Welcome to ned Productions (non-commercial personal website, for commercial company see ned Productions Limited). Please choose an item you are interested in on the left hand side, or continue down for Niall’s virtual diary.
Niall’s virtual diary:
Started all the way back in 1998 when there was no word “blog” yet, hence “virtual diary”.
Original content has undergone multiple conversions Microsoft FrontPage => Microsoft Expression Web, legacy HTML tag soup => XHTML, XHTML => Markdown, and with a ‘various codepages’ => UTF-8 conversion for good measure. Some content, especially the older stuff, may not have entirely survived intact.
- A biography of me is here if you want to get a quick overview of who I am
- An archive of prior virtual diary entries are available here
- For a deep, meaningful moment, watch this dialogue (needs a video player), or for something which plays with your perception, check out this picture. Try moving your eyes around - are those circles rotating???
You can find the posts here replicated onto Diaspora, if you prefer to subscribe there instead.
Due to being so busy, they could only spare me two days and those cost me more than six grand, but it certainly leapt me forwards a bunch. I got services ducting extended from their entry points at the driveway over to the western wall, specifically mains electricity, broadband, mains water and sewerage. 300mm of hardcore, crushed rock and a thin layer of gravel have been laid down. They felt that my wall was likely to fall down, so they pinned it with a new support column, which was made wide enough to plinth the solar inverter whenever it arrives, and they built up structural support for the far end which I had left open because concrete foundations needed putting in. That, in turn, meant I could seal and finish the ESB meter box, and it enabled me to install a 40ft shipping container:
This shipping container unblocks a vast array of other things as I finally have secure storage onsite – it was a critical blockage point, and without it not much else could proceed. As the photos show, it is a ‘new’ (once used) unit manufactured in China and it did a single crossing from China to Europe. It was expensive at seven grand, however used units are currently costing €5.5k, plus this specific unit is a High Cube rather than standard i.e. it is taller, and has 14% more space internally. I reckoned for the difference in it the slightly extra cost was worth it for a non-banged up unit that is guaranteed completely clean on the inside (which as the photos show, it is).
Most people now ask why buy instead of rent, as is normal for those in Ireland building a house? The reasons are: (i) I don’t expect to build for at least a year probably two as I wait out the coming recession, and rent vs purchase swaps value at around nine months (ii) I want to modify the container to add internal lighting, an alarm system, and forced air ventilation (iii) as a brand new container with modifications highly desirable by other Irish home builders, it should recoup a large portion of its cost when I sell it years from now.
This coming Monday the portable cabin should arrive, and once connected up that will finally give me a working toilet on the site, which would be amazing. And somewhere to shelter when it rains which isn’t my poor car! I’m going to wire it up so it’ll run off my petrol generator for the time being, then I can make cups of tea etc whilst sheltering inside from a deluge, which are common in Ireland. I have a small heat recovery ventilation unit coming for it, once I get electricity being generated onsite it should stop the cabin going mouldy as portable cabins tend to do if not frequently used.
Last few months I’ve been having to load everything in and out of my car per journey, plus my small rented house has been filling up with stuff purchased for the house. Being able to get some of that (the non-expensive stuff) out stored onto the site where it’s exclusively used would be most convenient and save considerable time not unpacking and repacking the car each time. Also, I was now able to order the solar inverter, the lithium battery storage, and the solar panels for the house as I finally have somewhere to store them. When they arrive (likely months from now, there are severe shortages of these items) I should be able to mount twelve of the panels onto the roof of the container, and that should generate 15 kWh of electricity per average day in December. That should be enough to space heat the portable cabin and run my work computer, and every month which isn’t December will generate far more electricity. I could just install mains electricity, however why pay its standing charge when I don’t have to?
In the past month or so I’ve found weekends and mornings before work to finish the construction of my wall, and because its mortar is so unstable due to my mistakes I needed to ensure it wouldn’t wash out with the winter rain, so I got a base coat of paint onto the inner side and I applied a cement and water paste to the outer side to seal the wall.
I’ll get two full coats onto the inner side before winter I would hope, weather permitting, and raise a one meter wide roof along ten metres of it which corresponds to the future outhouse. I’ll then be ready for whenever/if the solar inverter turns up to mount it onto the wall (you can see its plinth above).
Despite the delays in delivery of lots of critical bits, I suspect the single biggest constraint going forth will be my free time. I hope to invest as many mornings before work and weekends as I am either capable of or am allowed to. I’ll get there eventually, and once ready it will become my new place of work so I no longer need to work from home.
House build spend
My last update on this went up to 1st August 2022. I can tell you what the spend will be on the 1st October 2022, more or less:
- Spent: €157,769
- Committed to be spent soon: €15,448
- Current three month averaged spend rate: €12,096 per month
The four biggest ticket items in the past three months were: (i) Portable cabin (ii) Shipping container (iii) Groundworks (iv) Architect fees.
That is obviously rather a lot of money and most definitely is not sustainable – I am quite well paid, but burning twelve grand per month above living costs is very far beyond my means. The only good news is that this three month cash burn rate probably has peaked and will not become so high again until the main house build gets its deposit paid for it. And, I suppose when the inflation rate causes your cash to lose over 10% of its value per year, one of the best value preserving things you can do is get rid of your cash by swapping it for things which don’t lose their value as quickly. I certainly have achieved that anyway!
Apart from all the bitty stuff of wiring things up onsite etc, the next big thing is getting a mortgage application submitted. It is blocked on my company accounts and my 2021 tax return being completed. Hopefully that should happen soon, and we can set that ball rolling. Current backlogs mean we shouldn’t find out what our Approval in Principle value will be until maybe late November. Depending on what max borrowing limit they return, we might start searching harder for builders, or we might kick the can down the road for a year before trying another mortgage application and hope the house building cost proposition has become less insane. We shall see!
The reason I wish to speak of this phone is that my Samsung Galaxy S10 got itself into a boot loop on the first day I went on annual holiday in England, and given that I have ‘stuff going on’ right now and that my holiday rental has no wifi, I needed a burner phone capable of acting as a wifi hotspot for my laptop. I went to the local Tesco Superstore and bought the cheapest PAYG phone they had capable of a wifi hotspot, which was the Alcatel 1 2021 edition for £30 if bought with £10 of credit, which gives me 20Gb of data for the next month (a good chunk of which I have already used in a few days).
The Alcatel 1 phone has a terrible phone experience. It runs Android 11 Go, the edition of Android for low end phones, yet using it is like treacle. Assuming its touchscreen registers your tap at all, it can take up to fifteen seconds to react to your tap because it it so underpowered. It is capable of 4G, but lacks the processing power to download more than 250 Kb/sec or so due to its hideously slow storage. It has a TN panel display with almost zero readability off centre, it cannot be read at full brightness in direct sunlight, and it regularly misreads taps on the wrong items because you tapped sooner than it was ready for. Browsing the web on this device is truly horrible. Apps with any weight to them e.g. WhatsApp spend most of their time appearing to have hanged before eventually getting there. Even non-internet phone calls the phone can take so long showing you the accept or reject display that the call may time out.
The frustrating thing here is that with just a few minor tweaks, the phone experience would be acceptable. It has a quad core ARM Cortex A53 at 1.4Ghz, sure this is slow, but I know from my Android TV sticks that the experience doesn’t need to be like this. I would suspect that the storage is particularly shit, and if they fitted slightly less shit storage, the experience would be considerably better.
Equally, probably the £30 price tag would then get exceeded. I note that the next cheapest wifi hotspot capable phone that Tesco do is the IMO Q4 Pro for £60, double the cost of the Alcatel. For that you get on paper similar hardware specs, yet online reviews say it doesn’t suck anything like as much. I suspect that the cost difference went into storage and the higher resolution screen which is also IPS rather than TN, plus a bigger battery and better cameras. It sounds like an actually usable device as a daily driver, not masochistic like the Alcatel 1. Equally, for just £20 more again (£80), you can get yourself a Motorola e20 which has ARM Cortex A72’s and very decent hardware specs for that price point. As in, hardware specs which would have been near flagship apart from the screen only two years ago, though specification isn’t necessarily quality, albeit online reviews are extremely positive for the e20 for its price point.
As much as I am ragging on the Alcatel 1, I would have to say it is a whole lot of phone for the money. It does have a working GPS and Maps navigation, though I note that one’s position randomly wanders by about 20 metres, it does work. It does take pictures both front and back which are better quality than you’d think for a device at this price point: here is the ocean outside our rental plus a picture of me with Julia:
Those are not half bad considering. The latter picture was taken facing into sun, yet it did a surprisingly good job with applying dynamic illumination to the dark parts of the image.
Furthermore, it does make and take phone calls. You can send messages with it. It is a surprisingly good wifi hotspot, I get far better speeds from my laptop than it itself can do, I suspect because the wifi hotspot to 4G connection doesn’t touch its crappy storage.
Given that a decent dedicated wifi hotspot with 4G capability costs a lot more than £30 and doesn’t come with a battery, on that basis the Alcatel 1 is the best battery powered 4G wifi hotspot on the market by a long mile. On that assessment, this is a great bang for the buck device. Equally, I really hope that the next revision of their hardware chooses better storage. It would make one hell of a difference in usability as a phone. For now, this phone is very much a ‘little engine which could’ experience, as in, you’ll get there eventually, but you’ll be waiting a while.
(In case you’re wondering why I am buying the house solar inverter and batteries now which seems rather premature, it is because I need three phase demand in order to get the ESB to install a three phase mains supply. So I need these now if I am to avoid a second ESB mains installation charge, saving me €2k! Besides, the inverter actually lives outside, I’ll be mounting it on the wall I built below)
I have had the power at least to personally progress the bits I can do myself. To that end weekend before last I built my first concrete block wall in more than two decades:
I also got the temporary fencing raised at vast expense (I bought the fencing new rather than rented, it made more sense given how long I expect the build to take):
Whilst it was great to actually get stuff done instead of never getting replies from anybody, I am not the right person to be building concrete block walls! I was so slow at it that too much air got into the mortar mix from the concrete mixer, and that in turn made the mortar powdery rather than solid. It would eventually wash out with the rain, and then the wall would fall over, however I will be painting it well before then. It’ll do. I might also add that I pulled most of my upper body muscles, and their tendons all swelled up from the trauma. It was a great way of feeling old, unfit, and somewhat past it.
House build spend
It’s been three months since I purchased the site, so I can finally issue the first house build spend update! This will be a rolling spend average over the preceding three months, it will give an idea of the ‘velocity’ of the money flying out the door.
Up to 1st August 2022:
- Spent: €121,481
- Committed to be spent soon: €14,942
- Current three month averaged spend rate: €10,494 per month
This excludes the cost of the site, which was €90,000. The four biggest ticket items in the past three months were: (i) Stamp duty for land purchase (ii) Professional fees (architect, planning consultant, solicitor) (iii) Temporary site office deposit (iv) Aliexpress order of electronics for site lighting and three phase AC to DC conversion.
As I mentioned in the last post, I have spent well over €10k on components, a lot of which were sourced directly from China or directly from component manufacturers as bulk orders. It will cost me time to assemble this stuff by hand, and I need to wait many weeks for all of it to arrive, but it will save me a fortune overall.
Computer renderings of the future house
As mentioned last post, I invested several very late nights into mastering the conversion from Twinmotion into Unreal Engine 5. Unreal Engine 5 does a fair attempt at approximating ray traced quality images yet running at somewhat realtime speeds, at least on my anemic graphics card. I took these screenshots literally from the UE5 game I made of the VR model, and they are undoubtedly better than those from UE4, albeit with a few compromises over the (very slow) ray traced images that UE4 can generate. Note that this is derived from the February 2022 model, a number of small changes were made between this and what was submitted for planning permission.
Let’s start with an aerial view showing the entire site as a bird might see it. The lighting is accurate for April 1st at the exact latitude and longitude:
The main changes in what was actually submitted are additional skylights in the master bedroom (bottom right gable), and far more solar panels on the south roof plus more panels on the outhouse roof, as one needs explicit planning permission for so many.
These are the views from the main road looking at the front of the house and outhouse:
And these are from the back:
Walking in the front door through the lobby one enters the main living space, first entering the kitchen and then looking up:
Continuing from the kitchen past the greenhouse door into the living room:
UE4 didn’t do a bad job of rendering shadows, materials and reflections, but UE5 is very considerably better. Note that the ‘fur’ on the couch is actually furry. Note that the fridge’s stainless steel metal accurately mushes up reflections. Note that the kitchen island very nearly has perfectly accurate reflections, apart from a few rendering artifacts. And similarly, the shadows are complex, yet well defined and have an appropriate blur based on distance. All ‘for free’ in UE5.
Moving upstairs from the top of the stairs onto the bridge:
And then from the mezzanine looking down onto the Living Room – look at how well UE5 renders the reflections of the glass walls of the bridge, with the rightmost glass wall only having a partial reflection of the living room along its top because the bridge shadows the light from below:
The only other two rooms worth screenshotting are the Games Room and the Master Bedroom:
The games room image is another good example of UE5’s much improved light rendering. UE4 could only bounce white light without added effort from the designer, UE5 can bounce light based on the colours of the reflecting surfaces. So because the floor is brown, the light bounced onto the white ceiling is brown. If you adjust the season the sun beams land on the pool table and instead you get green illumination of the ceiling. All this also occurs ‘for free’ in UE5.
There are obviously more rooms in the house: kids bedrooms, shower-toilets, home office. But they’re bog standard rooms you’d see anywhere, so I didn’t bother taking screenshots. If you’d like to wander through the house in VR for yourself, I uploaded a copy to Twinmotion Cloud at:
https://twinmotion.unrealengine.com/presentation/xy1MGtTaLoDcB2Th Password: WLj1jHVq
How long that link will work for depends on Epic Games’ continuing generosity towards providing free cloud hosting and rendering for Twinmotion models, but for now it is good.
In a later post I’ll describe the POE-powered ESP32 based industrial microcontroller boards I ended up buying fifty of costing me over a grand, and how I plan to integrate those into Home Assistant. See you next time!
I’ll do a later post with pictures etc same as before, but tonight I’m going to be talking about some of the stuff I’ve bought for the house build. Since I took title to the land, I have spent as of today €9,952 on stuff for my land. Most of it will be deployed in some way before December, so it’ll be put to use soon. However other motivations were that inflation is eroding my savings at a cracking fast rate, so swapping cash now for inflation protected stuff I’ll need anyway is wise; also a lot of the stuff comes from Aliexpress i.e. China, and therefore takes two to three months to get to Ireland. So I order it now not needing it until October. I am not allowed to clear the site until September, but my hope is immediately after that to clear the site and do an initial set of groundworks to allow the placement of a temporary site office and a temporary storage container, along with installation and activation of services. I then order more stuff with long lead times, let them arrive on site over many months, and once the recession happens and prices become predictable only then will I start asking builders for quotes. Which is certainly a year away, could be more.
Next six months in any case will go on preparing construction detail by my team of designers. I’m currently seeking a Mechanical and Electrical Designer, and for the guy I have in mind I spent most of this weekend writing up this spec document, which others may find useful, so I post it here: My Passive House Plus Mechanical and Engineering Design Brief
My first new toy for the future house build: Security Cameras
Obviously a portable cabin and a storage container sitting on an empty site will be attractive to burglars, so I’m going to need security cameras to watch over them when I’m not onsite. The same cameras should watch over my house once completed, and be able to time lapse record its construction which I think will be fascinating to watch.
I didn’t have time to research what camera to buy, so I simply headed over to https://ipcamtalk.com/ and bought whatever they currently think is the best camera. Lazy I know, but I don’t have the time to do better. They think you ought to buy a 2K camera with 1⁄1.2 inch sensor, these have best in class unassisted night vision, however I really wanted a 4K camera for that twice better image detail. They have literally one choice in their recommendations for a 4K camera: the Dahua HFW5849T1-ASE-LED, also known as the Color 4K-X.
The forum has its own reviews of this model at https://ipcamtalk.com/threads/dahua-color-4k-x-in-depth-review.58999/ and https://ipcamtalk.com/threads/worlds-first-review-dahua-ipc-color4k-x-dh-ipc-hfw5849t1-ase-led-full-color-4k-camera.57013/, and yeah they basically think it the best new camera of 2021. As it is now 2022, the previous generation of cameras has seen price discounts and I picked up two of those with 3.6 mm lenses for €530 delivered to Ireland.
I gave them a quick test to make sure that they work. Here is my living space and kitchen in 4K crisp detail, mould patches and all in superb detail. Note how well the clock’s face resolves:
I now turn the lights off, and the camera automatically turns on its front warm white LEDs to add enough light to make a perfectly fine colour image:
It’s a little blown out by light reflection from the child’s playpen, but yes that’s a detailed, colour, image. Let’s turn off those illuminators:
What you can’t appreciate about the above picture is that it was completely black in that room. I could just about make out the window frames. I could literally see nothing else if I closed my laptop. Yet, this camera made that picture above. In case you’re wondering how blurry motion would be e.g. due to too much sensor gain, I waved my hand in front of it and whilst there was a little blur, it really wasn’t much. That camera just sees better than humans do, more like maybe cats do. It can see when you cannot.
Also note that it’s still a colour image! Note the detail in the tree branches outside – if you give any light at all to this camera, it’ll make good use of it.
I have to say that I am impressed. Mobile phones started seeing better than humans a few years ago, but it usually came with hefty motion blur and loss of colour and resolution. We’ve now reached a stage where there is undoubtedly a floor illumination level below which you get pretty much nothing, but as soon as you get slightly over that floor, you get oodles of detail and colour. Technology is still exponentially improving in this area for sure.
These cameras have a whole bunch of other clever stuff, like they can recognise humans and vehicles entering an area within the frame and send a request for a more powerful CPU to begin analysing the picture with AI. They have two way audio, they can play a really loud alarm sound. They aren’t particularly expensive either in my opinion for fully outdoor cameras. I am pleased with my purchase!
My second new toy for the future house build: Thermal Camera
You may remember my previous post when I received a FLIR One as a birthday present, and I found it very interesting to be able to see low infrared light. It had a resolution of 160 x 120, and via unofficial Android apps it was possible to unlock a 15 Hz frame update rate. Unfortunately, it didn’t last long, within a few months it had stopped responding when connected, so I sent it back for a refund, as it was not at all cheap if I remember rightly.
Thermal cameras are extremely useful for diagnostics of certain kinds of problem, and it is wise to record the construction of your house as it goes with a thermal camera, so problems discovered later can be more easily tracked down without expensively ripping everything out searching for a cause. To that end, I needed to buy a proper professional thermal camera, and I was displeased to find that FLIR cameras remain hideously expensive. Sure, you can recoup half the cost on the second hand market when you’re done with them, but that’s still a grand or so you’re blowing there.
I thus began looking for a ‘good enough’ substitute, some of which are US competitors to FLIR, some are Chinese marks. A recent new entrant to the thermal camera market is a Chinese company called HikMicro, which may or may not be related to HikVision (I suspect it’s a wholly owned subsiduary). HikMicro are most famous for their thermal hunting scopes which have been a huge hit especially in the US, because they deliver smooth thermal video, long battery life and high resolution for a small fraction of anything else on the market. No doubt like US made thermal equipment, there is a substantial military subsidy at work there making these cheap, but I’m not complaining as you’ll see shortly.
After much toing and froing, I eventually plumped for the just released – as in, last month - HikMicro Pocket 2 camera. This has a form factor just like a normal digital camera, with a large VGA resolution LCD touchscreen on the back, and it’s similarly point and shoot. It has a low infrared sensor of 256 x 192 pixels with 40 mK sensitivity and 25 Hz frame rate, a 8 MP visible light sensor, 50 degree wide field of view (most are far narrower), 16Gb of internal memory, dual band Wifi and USB C for transferring images, and is IP54 rated. You get all that for €700 inc VAT delivered at the time of writing, which sounds like a lot and it is. However the closest spec FLIR which is the E6-XT costs almost exactly three time more, and in terms of hardware spec is noticeably inferior to the HikMicro.
As is obvious, as a thermal camera the HikMicro is great – lots of resolution in there, often you don’t need the outlines generated from the visible camera to help recognition. You can set the temperature range manually before taking photos to ensure consistency across shots, and it’s tough to fault the hardware. The hardware is great value for money. The device feels fairly premium, a little plasticky, but definitely robust and the design is both well thought through and it looks swish as well. The waterproof membranes are a little obvious, but ensure you know it’s waterproof.
Let’s look at some images which diagnose a fault – here are the power wires leading up to my LED strip coving:
Let’s look at those in thermal:
Clearly, underneath the junction only one of the pairs of wire is carrying current, and it is mildly overloading the wire, raising it a few degrees above ambient. Above the junction, both wires are carrying current and therefore their temperature is ambient. I fitted two sets of wires precisely because I knew I would be pushing towards the current limits of this very cheap wire, and one set must have gotten knocked loose. As a diagnostic tool, this camera ticks every box you need.
Really it’s the software where things fall short, especially compared to the FLIR’s software. Don’t get me wrong, if you only care about taking thermal photos, this thing is great. A particularly cool feature is the device will do Wifi Direct and broadcast its image live, so you can connect in with you device of choice and watch the broadcast, same as you would with a smart TV from Windows or Android. From that you can then take pictures or record video. Nice touch! The HikMicro app slightly extends this facility with remote control, so effectively your phone becomes a remote control for the camera, which means you can stuff your hand with the camera down into really hard to reach into spots to get the view you want, then use your phone to remotely view and control it. This is a really great feature similar to FLIR’s premium Wifi capable models, and unlike the FLIR E6-XT, the HikMicro Pocket 2 is much less unwieldy to get into crevices. Just make sure you attach the wrist strap, lest it slip from your hand!
No, what I mean by the software letting it down is mainly these issues (note I tested the latest firmware at the time of writing, V5.5.25_220511):
- The UI is somewhat clunky and poorly designed, not really making good use of the touchscreen, and whatever software filter they have on the touchscreen makes it feel resistive instead of capacitive in terms of responsiveness (and yes, I did remove the screen protector it ships with, which does help).
- There is no way of recording video on the device itself, which seems extremely odd as it clearly can pipe video with audio to Wifi Direct.
- The hardware has a good microphone and apparently has a good speaker, yet the software makes no use of either. The microphone is piped into the Wifi Direct video just fine.
- The camera clearly captures and saves the whole visible image, 8 MP resolution if you choose that in the options. You can see that separate visible image when browsing the images on the device AND zoom into it by touchscreen swipe. Yet, you cannot access that image via any other means – you cannot export it, copy it elsewhere, access it. I tried the direct connection and the app. No joy.
- For some reason the fixed touch icons to the right of the screen are duplicated in the touchscreen UI, which seems redundant. Their backlight keeps turning off instead of dimming down, so you keep forgetting they are there at all.
- Exported images are always the VGA image shown on the screen in radiometric JPEG format. You get no other choice – you can’t access the original low infrared image, you can’t access the original visible image. You can’t get a 8 MP image with the thermal image stretched over the high detail of the visibile camera. Why not export all original data if they’re being stored on device anyway?
- I very much like that when you plug the device into a PC it appears as proper USB hard drive rather than as a MTP device like modern phones do. However, using a USB-C data cable to a USB-C laptop doesn’t work, nothing is detected. Only routing the phone’s USB-C port via a USB-B socket with a USB-C converter works. This makes me wonder if the device supports USB-C at all, and isn’t really USB3 with a USB-C socket?
As this is a just released device, improved firmware will undoubtedly follow, however I wonder if they’ll bother fixing most of the above before the next hardware refresh cycle occurs, whereupon they will surely want you to buy the newer hardware instead? I note that earlier thermal cameras in their range do have some of the above missing features, so I am assuming that this is a brand new firmware platform for them, and hence it missing features. Their firmware is a 128 Mb binary, so you’d really wonder what the hell they’re shipping in it given the lack of features.
Being a cynic, I suspect the potential of the hardware will remain unrealised, which is a shame, as for my house build record I’d really like to access the 8 MP visible images accompanying the thermal images. And capturing a thermal video with sound is useful on a windy day! Stll, as a straight shooting thermal camera this model ticks the box, and I am pleased with the cost benefit having tested it. I can live without video and original resolution visible images if it saves me €1,400!
I expect this time next year hard drive prices will have dropped back onto their long term trend line, and SSD prices perhaps will be flat. We shall see!
I called it right for hard drives, but I called it wrong for SSD prices which saw a better than trend improvement. Optane remained not just flat, but inflation adjusted flat which means Intel are proactively marking up Optane’s price with the inflation rate. Which explains why Optane remains a niche technology, as the performance per dollar gap between it and SSDs continues to grow .
Inflation in the past year in the US was something like 8%, so it is surprising that US dollars buy more hard drive and SSDs given the lack of inflation in the East where both are made. However, most raw materials and international trade is denominated in US dollars, so maybe inflation in the home market doesn’t necessarily mean loss of purchasing power outside it. After all, nobody is getting paid more, so Americans are getting poorer quicker than the Asian manufacturers whom only have to deal with raw material and energy price increases. In other words, the West is getting poorer quicker than the East because the West is seeing more generalised inflation, and I suppose that translates into a transfer of relative wealth from the West to the East. Thought about in those terms, I guess price drops could make sense from a Western relative viewpoint.
Looking forwards, it seems all but inevitable that price inflation will exceed 10% in the US and maybe even in the EU, though in Europe non-energy non-materials price inflation is being tamed by war’s effects on energy and materials supplies where outright lack of availability at any price means GDP is impacted, and that in turn dampens price inflation because the economy is weakened overall. I suppose where things get interesting is that lack of energy and materials supply also pushes up prices in the East, so I would assume that where computer components get manufactured is going to become rather more like Europe in the next twelve months i.e. everybody getting noticeably poorer because the cost of living substantially increases. That, in turn, probably means less demand for hard drives and SSDs, but also increased costs to raw materials and wages, so I’m going to suggest that both hard drives and SSDs will improve again this time next year as surplus capacity fights cost of manufacture.
The land transfer starts a countdown: In Ireland when you purchase land, you pay a stamp duty of 7.5%. If you commence the building of a dwelling house within thirty months from that date, you get a rebate because your stamp duty drops to 1% of the cost of the land and the building of the house less VAT. In my specific case, that’s worth about €1,500, so it’s worth aiming for.
The other big deadline is the end of this year: if I commence build before then, I get a €30,000 subsidy from the government. I very much doubt if we can get construction detail done before then, so we may have to think of some way of commencing a build before we know the precise detail of what we’re building. We’ll see how it goes.
A full nine months has elapsed since my last update on my P2P earnings #mintos! We’re running towards the end of this now I intend to start spending it – indeed, end of this month I’m going to disable the auto-invest and start letting the loans pay back into cash. It’ll take a few years for them to full pay back out, but from past experience a large majority will get bought out well before loan maturity.
|Month||Mintos annualised return for each month||Mintos non-earning capital||Moncera annualised return for each month||Afranga annualised return for each month|
A reminder that some money is tied up in non-earning Polish lender Capital Service, who will repay it eventually, but for now it drags down the annualised return rather significantly. If you exclude that non-earning capital, Mintos still does pretty well – I reckon about 11.5% in April, and I’m only investing in the super safe loans from DelphinGroup, which https://explorep2p.com/mintos-lender-ratings/ recommends highly.
Moncera (Placet Group) has been a bit of a disappointment since I started investing with them in March 2021, they’ve actually returned a touch under 10% annualised since the beginning. Around November 2021 I moved money out of Mintos because all the high quality loans there dropped to below 10% annual return. I moved them onto Moncera because they claimed theirs were over 10%. However there have been some cash drag issues, plus quite a lot of them have gone late, and that’s dragged down total return quite markedly. It’s not just Moncera, Afranga also saw cash drag and a large increase in failure to repay, most noticeable in the reduced return in April. So I suspect the war in Ukraine, higher living costs, and all the other kinda-recessioney stuff is beginning to bite in Eastern Europe.
Obviously, with inflation now running in the EU at 7% and climbing it rather ruins my strategy of keeping a portion of my cash in these p2p loans to offset losses to inflation. One is losing value in any case, and I’m going to need all my money by next year for the house build, so time to start winding all these down.
This may or may not be my last post on P2P investing. I may be coming into an amount of money soon which cannot be remitted into Ireland which will need placing somewhere. To explain, under Irish tax law non-domiciled people such as myself only pay Irish tax on monies I remit from outside Ireland into Ireland. All the money in these P2P investments to date has been post-tax money saved from income, but if I do come into money from outside Ireland then I’ll need to keep it outside Ireland so I don’t pay tax on it. These P2P lenders are domiciled outside Ireland and the loans are not invested in Ireland, so once my post-tax money has been paid out, I may reuse the accounts for pre-tax money. All this is months out whatever the case, but it may generate a few more posts here next year maybe.
(You may wonder why not put the unremitted money into an index tracking fund or mutual fund? Irish tax law currently ‘sees through’ non-domiciled status for investments in offshore funds domiciled in the OECD, which is pretty much all those which are safe, and taxes said offshore funds at a fixed rate of 41% rather than as income or capital gains. So you cannot put unremitted monies into offshore funds without creating a large tax bill. You might then think of shares in companies, but most countries charge a withholding tax on dividends, so they’re out. You’re now down to investing in gold, commodities or going synthetic with Contracts For Difference (CFDs) which are how you bet on the stockmarket – using CFDs you can synthesise an investment in something without doing the investment, and crazily enough the Irish tax authority is just fine and happy with that, which makes no sense to me. Because P2P lending is still too new, withholding taxes haven’t been levied on it yet, so for now at least this is an option)
Up until now capital preservation with easy access was the priority in my P2P strategy, so I have invested accordingly. If I wasn’t intending to remit investments for many years, then a very different P2P approach would make sense, one mainly based around secured lending. This should pay out around 11-12%, which is about what Mintos historically has done for me, but with much lower risk as collateral such as a building or a farm is used to guarantee loans. And if you want a bit more risk, you can also crowd purchase whole apartment blocks, take the rent from tenants as income, let the property value appreciate over a few years before exit. Then you can capture rising real estate prices in Eastern Europe, which is nearly a one way bet, at least compared to Western European real estate markets which see far lower growth.
And if you’re really keen on risk and have a long enough time horizon, there is p2p lending in aircraft leasing, artworks, sports cars and all sorts of niche things. Probably too rich for my blood, but glad to know it’s an option.
I am glad to report that the planners moved a bit quicker than expected, and we received notification three weeks ago that they intend to grant planning permission in early May if no appeals to the decision are lodged. If final permission is granted, then begins the process of purchasing the sites, which will take at least two months. I feel a little nervous about the purchase as sites have risen in price by about 15% since we agreed to buy them last year, plus I successfully cleared the previous planning blockers on that estate by getting local political representative John Paul O’Shea to intervene, so I have this horrible feeling that the sale will go wrong. Only when the land deeds are into my hands will I rest easier.
You can see the planning application and all the gory details at http://planning.corkcoco.ie/ePlan/AppFileRefDetails/224184/0, however to summarise there were only a few absolutely ordinary conditions imposed by the planner:
The proposed development shall be carried out according to the plans lodged.
A commencement contribution fee of €6,342.91 shall be paid to Cork County Council (this is based on internal square meterage of the property, and as much as it looks high, it’s less than half what it would be inside the city).
All new planting on the site shall be native in origin.
Any cutting of vegetation shall be outside the bird breeding season.
No muck nor debris to enter the public road from the site during construction.
Prior to commencement a connection to the public water mains is required.
To be honest, considering some of the conditions imposed by planners on previous developments in the same estate, these are very unimposing. Even only a year ago they were imposing a lot more onerous conditions. I suppose this is a new planner, from the preplanning feedback we really thought she was going to be even harsher, but in the end it turned out not to be so. I’m not complaining however!
The ecological report reckons the development could affect in the Blackwater Special Area of Conservation (these are protected under EU law):
- Floating river vegetation.
- Freshwater Pearl Mussel.
- Sea, Brook and River Lamprey (Eels).
- Migrating Salmon.
Of these, the Freshwater Pearl Mussel is the most likely to be impacted, despite them being about 60 km downriver. Indeed, in the application as I described last post I submitted a Habitats Screening statement on said Freshwater Mussels and how this development would not impact them. At that time the Council didn’t employ an Ecologist, which is why everybody had to contract one in, so I took a stab at writing my own report. That turned out to be superfluous to needs, but there was no way of knowing that at the time.
I guess the most surprising thing about the planning approval was the decision to permit materials other than smooth painted render everywhere. They permitted the low stone wall at the front, the charred wood in the middle, the zinc roofed porch, and the expansive glazing element at the front. They also had no issue with the large greenhouse at the back, and the entire of the south facing roof being solar panels. Surprisingly open minded of them.
The planning application for the larger twenty metre house went in a month ago, but it got bounced because I didn’t use yellow paper when printing the copies of the site notice in the application (I did use yellow paper on site). So I had to pay for another newspaper advert, reprinting and reerection of the site notices, and a bunch of other stuff had to be adjusted in the six copies of everything in the application, before I was able to resubmit it end of last week. Assuming it takes three months, that means we’ll hear back about it mid July, which hopefully will be around when I should get the title deeds into my hands. Obviously, if they just go ahead and approve that planning application, then it’s off to the races in terms of getting started on construction detail, but if they don’t approve, then we’ll need to figure out what to do next based on whatever the planner writes in their report as the basis for rejection.
In any case, none of this is anything worth worrying about for the next few months, so I can go focus on other things. My next non-work work task is proposing standardised secure sockets for C++, specifically the proposal paper for WG21. I need to bang it out using my very limited non-work time, and get it submitted and then that’s off to the races as well.
Then it’s all the other stuff I had hoped to get done or even started and I haven’t. Sigh. If only there were more hours in the week!
The preplanning feedback came back the week of Christmas, so we didn’t really get much time to digest it before everything stopped for the holidays. Things didn’t really get going until mid January, whereupon we started acting on the feedback (which I have slightly edited for privacy and clarity):
I have reviewed the proposal submitted and I would have the following comments to make in relation to same.
I note that the governing permission on the subject site is 00/4700. I would draw your attention to condition no. 3 of the original grant which notes the following
The construction of traditional type dwellings the siting, design, external finish and architectural standard of which shall be to the Planning Authority’s satisfaction and in harmony with the environment of the locality.
Reason: To ensure a satisfactory standard of design and layout for the proposed development in the interests of visual amenity.
I note the subject site is located within the development boundary, where the sites are zoned existing built up area. On this basis, the principle of the construction of a residential dwelling is acceptable.
In terms of the amalgamation of site no. 29 and 30 to facilitate the proposed development, I would have concerns in relation to the sustainable use of land and lowering the density of development within a defined settlement boundary. A strong justification for the amalgamation of the sites would need to be put forward at application stage, this should include analysis of no. of serviced sites available within the settlement boundary.
In terms of design of the proposed development, it is noted that the specifics of design and layout are usually addressed at application stage. However, I note drawings have been submitted with the preplanning request. On this basis, I would have the following comments in relation to same
- I would have concerns in relation to the overall scale of the proposed development in the context of the existing housing estate. The overall scale of the proposed development would appear from the submitted drawings to be excessive given its context within the existing housing estate and it would not be considered to be keeping in character with the existing dwellings in the estate.
- I note that the housing development comprises various styles of dwelling, however, there is still an overall general consistency of appearance. While a more contemporary dwelling could be considered at this location, it should still aim to be consistent with the general appearance and character of the dwellings in the vicinity of the sites.
- I would also refer to the condition no. 3 of the governing permission set out above which required traditional type dwellings.
As an update on the WWTP in the village, it is considered that there is some capacity within the treatment plant. However, all applications looking to connect to the plant going forward will be referred to the Executive Scientist and Ecologist. There is not too much more that I can say on this at this stage, however, updated information may be included in the new Cork County Development Plan which is set to be published in early 2022.
If the above seems vague, non-commital and rather hard to discern exactly what they want changed, that would be normal for preplanning feedback – nailing colours to a mast removes later flexibility. That said, after a bit of thought and study their feedback could be rewritten into more concrete terms thusly:
Despite that the current style guide is the 2011 guide (very shortly to be replaced with the 2022 style guide), we want this house to meet the 2001 style guide because that was the guide in force when the estate’s original planning was granted, and the existing houses were theoretically built according to that style.
(The reason this matters a lot is that the 2011 style guide bans gables, whereas the 2001 style guide effectively requires gables. We designed towards the current guide (i.e. gableless), so now we need to redesign around gables jutting out everywhere!)
No materials to be on the outside except light coloured smooth painted render, as that is what all the other houses in the estate are supposed to be (and which most certainly are not, as they acknowledged).
They don’t like the idea of one house spanning two serviced sites in a way which permanently reduces housing density, but left open a possibility that they could be persuaded if it did not set a precedent others could later reuse.
They think the proposed house and its framing too big.
Planning applications submitted from 2022 onwards will require an Ecological Impact Assessment, and one will need to prove that how one connects to the WWTP will not impact the Blackwater Special Area of Conservation which is protected under EU law.
To deliver on these we did:
Gable-ified the design, particularly the ‘shrunken’ house (more below).
Removed most of the non-smooth-painted-render materials, and shrank the area of what remain.
Made a second design of the house fitting into a 17 metre width rather than its original 20 metre width so it can fit into a single site. This ‘shrunken’ house became our fallback plan, the conservative option likely to get planning permission. It is this I submitted last Tuesday for Site 30 only.
Also, given the phrase ‘A strong justification for the amalgamation of the sites would need to be put forward at application stage’ it became obvious that we would need to hire a specialist Planning Consultant to help us write the planning application for the 20 metre house i.e. a former Planner who knows how to write in Planner-ese. Alas, Planning Consultants are expensive, quotes came in between €800 and €5000 some with long lead times. We ended up choosing a lady who could get started within a few weeks for €3000.
Removed the extended framing from the 20 metre width house and built it up higher with gables in order to make it look shorter and less different from the other estate houses.
I wrote a Habitats Directive Screening statement which followed the EU framework for describing how we will impact the Blackwater Special Area of Conservation both during construction and during the lifetime of the house. One normally pays an ecologist €800-1000 to write one of these, I cobbled mine together by exhaustively assembling all the Habitats Screening statements from preceding planning permissions in the same area, and I replicated the same points they made using similar language, but also customised it slightly to describe how our rainwater harvesting tanks are good for the Freshwater Pearl Mussels 64km downstream in the Blackwater by attentuating stormwater surges to the WWTP etc etc. We shall see if that sticks!
The ‘shrunken’ design
This 17 metre design looks very much like the 20 metre design submitted for preplanning I showed pictures of last post, but we had to make a fair few changes:
The loss of three metres of width means more spillage of floor space into depth, so both front gables come out a little further and a whole new gable appears in the back.
As we no longer have the width to put the home office over an internal bridge into the upper floor west, the eastmost front gable goes to two storeys and the home office goes into the upper floor there instead.
As the internal bridge no longer makes sense, the main vaulted living space area gets both wider as well as shorter. This makes a master bedroom infeasible in the westmost front gable, so we move the plant room in there as it is now comparatively small. The master bedroom now goes into the rear gable.
Otherwise, apart from size changes, things remain as they were, though energy efficiency according to the PHPP takes a dive of about 20% because there is much more surface area than before for less internal floor area. Also, the margin for minor builder error in airtightness to reach the Passive House Plus standard shrinks from 40% to a mere 24%, a 67% reduction .
I am fortunate that Twinmotion 2022 beta had come out since the last post, and using it I was laboriously able to make ray traced images this time. They look a lot better than those from the previous post, though I had to dial down the quality settings severely given my emaciated graphics card. Note that these are missing the greenhouse on the back and a few other minor changes.
There is also the master bedroom and the games room:
Heading out of the master bedroom, which has a door opening into the back garden, the back of the house is remarkable only for the number of solar panels on the roof:
A reminder that the lean-to greenhouse on the back was yet to be added, and the green ethereal building next door is a hypothetical house. Moving around to the front:
As you can see, we have hacked back the surface area of unapproved materials severely, with the northern glazing column reduced from three wide panes to two narrow ones, and the bottom half broken into a forward extended metal porch, albeit without much metal showing. This shrunken design surely should tick the planner’s boxes.
Now that the shrunken design on the single site 30 is submitted, our next task is to prepare the planning application for the 20 metre wide house in collaboration with the Planning Consultant. No doubt she will write the application in a way that if it gets rejected, it is designed to go straight into An Bord Pleanala, the national appeals mechanism for planning. That takes a further four months and yet more money in fees of course.
However there is a third option – submit a third planning application for the same land, this time with the shrunken house occupying Site 29 but with the boundary around both sites, possibly also with the outhouse from the slightly larger house. It can thus be argued that Site 30 has not been consumed nor made unavailable for future development in any way. Whether this is worth doing, or is feasible, depends on how the Planners react to the 20 metre wide house: if their primary objection is that the extra three metres of width renders the other site permanently consumed, or that three metres longer makes the house too bulky compared to neighbouring houses, but otherwise they don’t object, that would seem the obvious path forwards. If, on the other hand, it is the fundamental principle of granting planning on amalgamated sites at all as it would set a precedent, then it probably doesn’t matter what you put on those two sites. We’ll only find out when the Planners deliver their verdict.
Assuming that getting a verdict on the single site application will take four months, that puts a decision into June, with a decision on the dual-site application probably landing in July. Completing the purchase of the site might take two months starting from June, so nothing more could happen anyway until August. If it then goes to An Bord Pleanala, I suppose concurrently we submit planning application number three and we should hear back from both of those around December 2022. We then could begin detailed construction drawings which I can’t believe would take anything less than four months, probably six months, given that the Energy Consultant will be in there, as will a M&E consultant and probably a garden designer. Thus only in June 2023 would one be ready to approach builders for construction quotes as the upper bound, with the lower bound no earlier than January 2023.
Both are rather a long time away, though almost certainly by then price inflation should be getting tamed by interest rate rises and a slowing economy should debottleneck materials and labour supplies. I’m also not entirely sure that even if we booked construction by the end of this year would it actually speed anything up given the backlog in the self build industry, though it would almost certainly cost us more. So, in all probability, it will be 2024 no matter what we do before construction begins.
My original plan was to build the outhouse first and install services into it, this would let me commence building and thus be eligible to draw down €30k of government subsidy, lest the government reduce that next budget. I’m also minded that commencing the mortgage sooner rather than later would lock in a lower fixed interest rate for the first five years. Might it be doable by September of this year, give it two months to get approved, then submit commencement for December in order to claim the subsidy? Maybe, though it’s a bit tight.
Let’s just hope that the government extends the subsidy into 2023!
So yeah, I just went ahead and inputted the house design into PHPP v9.6 straight away and this post is about what it spat out, because it contains quite a few surprises. To remind folk so later makes sense, we intend to meet the Passive House Classic standard and the RIBA 2025 challenge for this house, with stretch goals for the Passive House Plus, the RIBA 2030 Challenge, and the Passive House Premium minus PV generation:
Irish 2019 NZEB BER A1 House
German Passive House Classic
RIBA 2025 Challenge
|Stretch goal 1:|
German Passive House Plus
|Stretch goal 2:|
RIBA 2030 Challenge
|Stretch goal 3:|
German Passive House Premium
|Heat & Ventilation Energy:||≤ 25 kWh/m2/yr||≤ 15 kWh/m2/yr|
|≤ 15 kWh/m2/yr|
|≤ 15 kWh/m2/yr|
|Air Leakage:||≤ 3 m3/hr/m2||≤ 0.6 air changes per hour|
|≤ 0.6 air changes per hour|
|≤ 0.6 air changes per hour|
|Wall & Floor Insulation:||≤ 0.18 W/m2K||≤ 0.15 W/m2K|
|≤ 0.15 W/m2K|
|≤ 0.15 W/m2K|
|Window Insulation:||≤ 1.4 W/m2K||≤ 0.8 W/m2K|
|≤ 0.8 W/m2K|
|≤ 0.8 W/m2K|
|Total Energy Use:||≤ 120 kWh/m2/yr||≤ 60 kWh/m2/yr|
|≤ 60 kWh/m2/yr|
|≤ 45 kWh/m2/yr|
|≤ 35 kWh/m2/yr|
|≤ 30 kWh/m2/yr|
|Embodied lifecycle carbon emissions:||≤ 1200 kg CO2e/m2||≤ 800 kg CO2e/m2|
|≤ 625 kg CO2e/m2|
|Potable water consumption:||≤ 125 litres per occupant per day||≤ 95 litres per occupant per day|
|≤ 75 litres per occupant per day|
|Indoor CO2 levels:||≤ 900 ppm||≤ 900 ppm|
|Indoor VOC levels:||≤ 0.3 mg/m3||≤ 0.3 mg/m3|
- Passive House Classic is a low energy house, approximately twice better than the current best rated house under the 2019 EU Near Zero Energy Building (NZEB) regulations (Passive House Classic long precedes EU NZEB, and indeed strongly influenced the design of EU NZEB which is why they look so similar).
- Passive House Plus is a net zero energy house, over a calendar year it generates about as much energy as it consumes by generating energy in summer and consuming an equivalent amount in winter.
- Passive House Premium is a net generating house in that it contributes much more to the grid than it consumes. Because in Ireland there is no feed-in tariff for solar PV, and when they introduce one next year it will pay at desultory rates and has a low annual cap for maximum payment, it is not economic in Ireland to generate much excess electricity on-site. One can still aim for a stretch goal of ≤ 30 kWh/m2/yr total energy use however, and to put that in perspective, what an Irish BER A2 rated house uses only for space heating is what a Passive House Premium uses for everything – cooking, showers, all electricity use etc.
How I configured my PHPP model
Firstly, I must stress the following:
- I have never taken the Passive House Designers Course.
- I basically just filled in the PHPP v9.6 spreadsheet using common sense, a fair bit of head scratching, and occasionally peeking inside the equations to figure out what the hell they mean and/or what the error messages were going on about.
- I did not invest time on inputting detailing such as thermal bridges nor exact shell layer composition.
What I modelled:
- Climate: PHPP defaults for Cork Airport in Ireland, albeit with altitude reduced to my site’s.
- U-Values: Three building assemblies of a single 0.5m thick shell giving a u-value of 0.147 W/m2K, each for ground floor, first floor, roof.
- Areas: Fairly close approximations of shell areas from plans.
- Ground: Fairly close approximations of shell areas from plans with u-value of 0.11 W/m2K. I left all other values at suggested defaults.
- Components and Windows: I approximated Munster Joinery’s Passive House range of windows and doors, Velux’s Passive House range of roof windows, the Zehnder ComfoAir 550 as the MVHR, and the ShowerSave 20 ltr/min waste water heat recovery unit. As per the design described in earlier posts, there is no heat pump employed here.
- Shading: I put full temporary sun protection on the south facing roof windows, as these will have external mechanical shutters. I put 70% shading on the south facing wall windows due to an external mechanical blind on the games room and the summer plants in the greenhouse.
- Ventilation: As my site is windy, I chose a moderately protected site with wind hitting it from all sides. I set the worst possible air tightness, 0.6 ACH, and made the shell air tightness layer somewhat elastic by 10 m2 for the whole house. I configured 30 m3/hr of ventilation per person, and chose its suggested default of 180 m3/hr of ventilation for the house. I told it to run that constantly for 24 hours per day. I chose two metres of inlet and outlet air ducts, and a subsoil heat exchanger to represent the earth tube with efficiency of 60%. It reckons that with all that combinated, the total ventilation system should achieve 75.2% effective heat recovery, with the earth tube basically paying for the other losses around the 75% raw efficiency of the MVHR unit.
- Summer Ventilation: I configured an automatic bypass of the heat recovery on the MVHR, and set a 0.32 ACH for ventilation which is +50% of the winter ventilation, as suggested by the help box. Unfortunately the subsoil heat exchanger doesn’t appear to be factored in, so to account for it reducing the incoming air by maybe 60% of the difference to ground I increased that ventilation to 0.66 ACH to make the numbers come out about what look to me about right for a 0.32 ACH via a long deep earth tube.
- Domestic Hot Water + Distribution:
- For Space heat distribution I configured 10 m of distribution pipe of 15 mm diameter with 24 mm 0.04 W/mK insulation @ 75 C temperature. Radiators are best run at 55 C to prevent them producing a scalded metal smell – or indeed burning people – but a thermal store sits at 75 C, so I have to choose 75 C here (in practice one would use a thermostatic mixer drawing from both the top and bottom of the tank to reduce the radiator temperature).
- For DHW useful heat I left the defaults as was (16 ltrs/person/day for showers, 9 ltrs/person/day for hot water) but configured a shower drain water heat recovery unit as described earlier for a 16 ltr/min ten minute long average shower with heat recovery into the cold water feed for the thermal store’s DHW inner tank and the shower cold water feed. This gave a 55% whole system shower heat recovery.
- For DHW distribution I left the flow temperature at 60 C, and configured 20 m of circulation pipe of 15 mm diameter with 24 mm 0.04 W/mK insulation. I added a further 10 m of individual pipes off the DHW circulation pipe with six tap openings per person per day every day of the year.
- For Storage heat losses I chose a DHW and heating tank with 5000 litres capacity @ 75 C to represent the thermal store. Assuming a 2x2x3 metre airtight box insulated with Kingspan Sauna Satu with a u-value of 0.023 W/m2K = 20 m2 that gives a heat loss rate of 0.46 W/K.
- Photovoltaics: I configured sixteen of my cheap 375w Trina honey solar panels on the south facing roof at a 35 degree slope under the assumption that more cheap panels is better than fewer expensive panels. This has a maximum generation capacity of 6 kW. PHPP lets you enter their detailed functionality such as crossover voltage and the inverter’s details, and it thinks this install in my climate and this house would generate 6023 kWh of electricity per year for a materials cost of €4.7k, which is equivalent to €0.04/kWh if amortised over twenty years.
- Electricity: I left the defaults for all the appliances as-is, except to add an always on computer server consuming 875 kWh of electricity per year.
My PHPP model results
Yeah, so PHPP is ridiculously detailed:
|Heating degree hours - External||10.9||9.7||9.9||8.6||7.0||4.9||3.7||3.7||5.0||7.2||8.9||10.5||90||kKh|
|Heating degree hours - Ground||6.0||5.7||6.3||6.0||5.3||4.7||4.4||4.1||3.9||4.7||4.9||5.5||61||kKh|
|Losses - Exterior||1428||1281||1307||1134||923||643||486||488||652||943||1173||1382||11840||kWh|
|Losses - Ground||197||185||207||196||180||162||156||149||142||165||168||186||2093||kWh|
|Solar gains - North||64||80||170||257||364||398||379||279||204||121||72||48||2436||kWh|
|Solar gains - East||8||9||19||32||39||41||37||28||23||14||8||6||264||kWh|
|Solar gains - South||355||335||535||743||726||687||640||602||636||473||395||295||6421||kWh|
|Solar gains - West||27||35||68||114||129||126||114||99||89||55||35||24||914||kWh|
|Solar gains - Horiz.||0||0||0||0||0||0||0||0||0||0||0||0||0||kWh|
|Solar gains - Opaque||52||63||124||203||240||248||226||185||154||95||62||42||1695||kWh|
|Internal heat gains||458||414||458||443||458||443||458||458||443||458||443||458||5396||kWh|
Of the heat losses due to the shell, 929 kWh per annum is lost by ventilation (both intentional and unintentional). The southern glazing accumulates the most heat for obvious reasons, however due to the extensive raised high northern glazing it’s not a small accumulation there, which I found surprising. Internal heat gains (appliances, showers, cooking, people etc) are substantial, and you’ll note they are constant throughout the year. This is ‘baseline’ heating, and too much of it will cause overheating in summer.
Speaking of overheating, PHPP thinks it will be minimal, on four days per year (0.9%) in July might internal temperature exceed 25 C. If I add external blinds on the northern glazing that does fall to 0.5%, which probably isn’t cost beneficial.
Of the 5396 kWh per annum of internal heat gains, 4127 kWh is from electrical appliances and the remainder comes from the thermal store losing heat (222 kWh), domestic hot water (1055 kWh) and the remainder is distribution losses. In terms of monthly, that’s 344 kWh/month electrical appliances and 88 kWh/month domestic hot water.
Finally let’s look at the photovoltaic gains from the roof solar panels month by month, and note that the solar panels will generate more electricity than the house uses for everything for the months of April - September. This will be important, as you shall see later:
|Solar radiation on tilted surface||44||51||95||147||160||158||145||127||116||75||52||35||kWh/(m²month)||1204.9||kWh/(m²a)|
|Total monthly yield||221||258||478||742||800||784||715||629||577||377||262||179||kWh/month||6023.2||kWh/a|
|Losses through shading situation||0||0||0||0||0||0||0||0||0||0||0||0||kWh/month||0.0||kWh/a|
Does PHPP think this house design meets our goals and stretch goals?
PHPP thinks this house design has a Primary Energy Renewable (PER) demand of 38 kWh/m2/yr, which is well under 60 (Passive House Classic) and 45 (Passive House Plus). It is not low enough (though see later) for RIBA 2030 nor Passive House Premium.
Showers and sinks it thinks will consume 25 ltrs/day/person of hot water, which is about 30 ltrs/day/person once mixed with cold down to 40 C. Toilets are supplied by rainwater, so most of the remaining potable water use will come from washing dishes or clothes. Assuming the washing machine and dish washer are run once per day, that adds 15.5 and 4.5 ltrs/day/person, giving a total of 50 ltrs/day/person. Assuming that cooking and drinking water wouldn’t exceed 25 ltrs/day/person, I’d say the RIBA 2030 challenge for potable water use should be met.
The RIBA 2030 Challenge embodied lifecycle carbon emissions is mostly down to what building material you choose – concrete is very bad, wood is good. If you choose wood for everything, unless your builder does something really weird, one should come in easily under 625 kg CO2e/m2.
Finally, because 6kW of PV panel doesn’t generate enough electricity, we don’t meet the generation requirement for Passive House Plus (it requires generation ≥ 51 kWh/m2/yr if PER demand ≤ 38 kWh/m2/yr, which ours just about meets). We would need to fit +50% more solar panels to meet the generation requirement.
Correcting the Primary Energy Renewable (PER)
As I mentioned on a few occasions now, PHPP assumes that you feed your excess PV generated electricity back to the grid. It has no facility for indicating that you’d want to do anything else with that excess electricity e.g. heat the thermal store so nighttime electricity doesn’t have to. An added wrinkle for Ireland is that there will be a cap on the payment for your contributions to the grid, at the time of writing the details are not clear, but it seems that the rebate will be capped to 30% of your total including PV electricity consumption (how they are going to validate this is beyond me, but that’s the current thinking apparently).
We need therefore to correct PHPP so as little nighttime electricity to heat the thermal store is used as possible, which by definition will lower total direct electricity usage and therefore reduce PER demand.
My 5000 litre thermal store if completely full @ 75 C contains 322 kWh of space heating or domestic hot water. One would keep no less than 50 kWh of space heating hot each night, so that leaves 270 kWh to buffer sunny days across overcast days. I thought it would be interesting to also model a 3000 litre thermal store, which contains a maximum of 193 kWh and so its buffer is 143 kWh.
Annual figures from above:
- Total electrical appliance usage: 4128 kWh
- Total space + DHW heating: 3723 kWh
- Therefore total house electricity consumption: 7851 kWh (+ 841 kWh for pumps, ventilation etc)
- Estimated electrical appliance replaced by PV solar during daylight hours: 1296 kWh
- Estimated ‘spare’ PV solar electricity which normally would feed into grid: 4727 kWh
From this we can say that the feed in payments will be capped at 2355 kWh per year, which at €0.065/kWh is €153.
|Max electricity supplied by solar for electrical appliances during daylight||47||55||102||158||172||170||156||137||125||81||56||38|
|Solar electricity remaining||174||203||377||584||628||614||559||492||452||296||207||141|
|Domestic hot water heating||88||88||88||88||88||88||88||88||88||88||88||88|
|Tank days between sunshine||6||7||13||30||30||30||30||30||30||24||10||5|
|Thermal tank contribution||-671||-528||37||454||533||526||471||404||361||117||-345||-717|
|Thermal store capacity||50||50||87||193||193||193||193||193||193||193||50||50|
|Mains electricity contribution||87||101||188||348||533||526||471||404||361||117||103||71|
|Mains electricity demand||-968||-818||-242||-186||-172||-174||-188||-207||-219||-263||-490||-1023|
You might notice the ‘Tank days between sunshine’, this is the average number of days that the buffer in the tank can supply all space heating and domestic hot water for the average day in that month. So, if in December it were -6.8 C, the store would run out twice quicker as that is double the differential from the monthly average, whereas if were +13.3 C, the store would run out twice slower (this being half the differential from the monthly average). The 3000 litre tank gets you a bit less than a week in winter average i.e. sunny days, which tend to come in bursts in the Irish winter, need to occur at least once per week. From experience I find this rather too optimistic, so I’ve assumed that due to the limited spare capacity in the thermal store, in the winter it will only capture half of the sunny days and the rest goes back to the grid.
Annual for 3000 litre tank:
- Estimated mains electricity contribution as thermal store was full: 3310 kWh (45% reduction, due to cap earns €153)
- Estimated mains electricity demand from appliances or because thermal store was empty: 4951 kWh (37% reduction, or €288 of night rate electricity saved)
|Tank days between sunshine||11||13||24||30||30||30||30||30||30||30||18||10|
|Thermal tank contribution||-584||-427||37||454||533||526||471||404||361||117||-242||-646|
|Thermal store capacity||50||50||87||322||322||322||322||322||322||322||80||50|
|Mains electricity contribution||0||0||0||219||533||526||471||404||361||117||0||0|
|Mains electricity demand||-881||-716||-242||-186||-172||-174||-188||-207||-219||-263||-288||-922|
‘Tank days between sunshine’ is nearly double for the 5000 litre tank, and I think it likely that a burst of sunny days would occur every ten days or so in winter, so the thermal store should be able to absorb all excess PV.
Annual for 5000 litre tank:
- Estimated mains electricity contribution as thermal store was full: 2631 kWh (44% reduction, due to cap earns €153)
- Estimated mains electricity demand from appliances or because thermal store was empty: 4459 kWh (43% reduction, or €339 of night rate electricity saved)
Something interesting here is that a 5000 litre tank is only about €600 more than a 3000 litre tank, so that is a payback time of twelve years or so given the electricity savings of €51/yr.
In any case, for either size of tank diverting excess solar to the thermal store makes a big difference to mains electricity consumed, primarily because all domestic hot water is covered by solar PV. If we adjust PHPP’s PER worksheet to add a ‘Thermal storage’ offset of mains electricity consumption, with 100% of DHW supply from the solar panels throughout the year and the remainder offsetting space heating:
- For 37% demand reduction (30% of space heating, 100% of DHW) of 3000 litre tank, PER demand drops to 26.9 kWh/m2/yr.
- For 43% demand reduction (48% of space heating, 100% of DHW) of 5000 litre tank, PER demand drops to 24.4 kWh/m2/yr.
Both of these are under Passive House Premium’s maximum energy consumption of 30 kWh/m2/yr, so in this sense both stretch goals 2 and 3 have been reached. However because the generation of electricity by the house is far below what it consumes (1627 - 2188 kWh), it does not meet the minimum generation requirements, and therefore Passive House Plus (let alone Premium) is not achievable.
As much as fitting +50% more solar panels looks tempting to reach Passive House Plus, that adds an additional capital cost of €2.2k or so, and because of the feed in cap, the effect of the added generation on our annual electricity bill of a mere €1000 or so is not going to be much. In other words, it’s not economic. Equally, for just a small added capital outlay one might fit an oversized solar inverter, and if the government in the future remove that cap, adding more solar panels later is easy.
Why did my crude model overestimate total energy consumption by so much?
Summary of my hand made crude model from the last post:
- Primary energy demand for the proposed house would be around 11,000 kWh.
- This is for 260 m2 of living space, which gives a 41 kWh/m2/yr which is well below the limit of 60 kWh/m2/yr required for Passive House Classic, and is even below the 45 kWh/m2/yr limit required for Passive House Plus.
PHPP came in at 79% total energy use of my crude model. There were two main causes:
- My crude model assumed far more DHW goes on showers. This is because I forgot to scale the numbers for hot water consumption only (I used total flow), and also because I modelled five adults, whereas PHPP hardcodes modelling 3.2 adults.
- My crude model assumed more air leakage due to doors being opened and closed etc.
- I had basically put a smoothing estimator for the thermal store rather than anything more rigorous like the above, and whilst not a bad estimation for me effectively sticking my finger in the air, it was a bit off.
If I fixed those, it pretty closely matched PHPP which was reassuring!
Anyway, I’m glad to report that our house design is finally done. After a mere five months to secure the rights on our site, our architect Stephen O’Leary from Cork based Rebel Design Studio only could get started these past few weeks. As you may remember, in my original post in August, I had already had a crack at designing the whole house, including layouts internal and external, designing its ventilation, heating and electrical systems, and I had prepared a thirty-five page brief dense with detail. Stephen took that design and rendered it into 3D, along with a few variants and then finally a fourth design which was entirely his, albeit thematically similar.
Getting the VR headset to view architecture
I had bought an Oculus Quest 2 specifically to wander around these concept designs in VR, so I tried importing the Twinmotion renders into Unreal Engine 4 and then generating an Android mobile binary targeting the Oculus. Unfortunately, Oculus’ Android doesn’t implement Mobile HDR, and when you disable HDR, all the Twinmotion assets render as sheets of entirely all white or all black – i.e. useless. If you enable Mobile HDR, the binary doesn’t work on the Quest 2 at all.
This was rather unfortunate, so I had to fall back to the Oculus Rift emulation function of the Quest 2 whereby a PC renders the VR and the image gets blitted over a USB cable to the headset. Alas the Windows Oculus software sucks monkey balls, it just silently refuses to work if you don’t get everything exactly right, and it provides zero help messages nor clues as to what is wrong with it. Literally trial & error black magic to get it working. Awful experience, but I got there in the end mainly through a lot of Google searching of people having the exact same awful experience as me. Thanks Facebook .
Unreal Engine 4, at least if you stay on the PC, works really rather well in VR with very little added effort, and my recently bought AMD Radeon 6600 XT renders such simple 3D models as these like butter. Without me coding anything up, it’s a very basic experience, you esssentially fly around with the keyboard and you have free range look with the headset. But, it’s enough to get the job done in terms of evaluating the concept designs.
Yes, Twinmotion also has a VR viewing option, but if you try it you’ll find it sucks. As it’s also UE4 based, I have no idea how they managed to make it suck so badly. In any case, importing your Twinmotion file into UE4 is so straightforward it’s the obvious workaround. Also, if you package up your UE4 game into a standalone binary, even a laptop with Intel integrated graphics will do a passable job of rendering it, whereas for some reason Twinmotion’s standalone viewer binaries suck badly on Intel integrated graphics. Again, same bloody engine, no idea why it’s so bad.
(Incidentally, if you’d like UE4 to make it look really pretty, try turning on ray tracing. Looks gorgeous on the outside, but inside everything’s too reflective, and I didn’t find the time to figure out how to dial back so much reflection. The pictures below were rendered actually by my laptop’s Intel integrated graphics using a standalone packaged game without ray tracing enabled)
My original design
Stephen had rendered my original design mostly as I had it into 3D. The general design was that of a bungalow, but with victorian style raised ceilings on the ground floor, and a reduced width loft conversion upstairs spanning three quarters of the house length. The design showpiece was a roof to floor open vaulted space for the living area, with a raised mezzanine reading and library area overlooking it. I had chosen the golden ratio for width to length, but I had been worried that it just wasn’t wide enough to have the ‘church hall’ effect I was seeking. Looking at the images without VR it seemed reasonable (note these are rendered by BIMx not Unreal Engine):
Once into the VR however, my fears were confirmed: the vaulted area felt ‘pokey’. Stephen’s rendition deviated from my original design, I actually had the vaulted space wider, and the mezzanine was lower and jutted into it around the middle, all of which was going to require expensive steel beam structural support. However, his wasn’t a million miles away. The problem was – and it was only really obvious once in VR – that the height to width ratio just wasn’t there, and as the house already had a 180m2 footprint, and I wanted all bedrooms on the ground floor, extending it another five metres just for the main living space seemed inefficient.
Another issue was that I had chosen a ten metre wide building, which leaves nine metres wide internally (the raised ceilings were to admit additional light to compensate for the added width). Stephen was adament that this would not fly with planning, who seek eight metre wide buildings. I know that some rural one off houses get away with ten metres, but as we are building on an estate, the best Stephen felt possible was a roof not peaking in the middle such that the front roof of the house would match the others on the estate, and the back roof would be consequently much longer and steeper as a result in order to stretch the width out to ten metres.
That seemed reasonable, but it rather ruins the roof symmetry of my original design in an unpleasing way. As you’ll see later, Passive House Plus (< 45 kWh/m2K) isn’t achievable without the ratio of total house shell area to floor space being below a certain ratio, and the eight metre maximum width requirement makes that virtually impossible. Passive House Classic (< 60 kWh/m2K) is still just about within reach however.
The final design as being submitted to preplanning
Stephen’s own design had taken my original concepts and done something rather different with them: If you imagine an S-shape whereby your living room opens up into the vaulted height as you approach the kitchen, the kitchen terminates the ground approach but then you sweep upwards onto your mezzanine library reading area, that’s pretty much Stephen’s design. The clever thing here is you now get the width proportional to the height that my design was lacking – actually, you get oodles of width, it’s about 2x width for the height, but as it’s an S-shape, it breaks up that width in a fluid flow.
Obviously, using so much of the house’s length and height to achieve this effect leaves insufficient space for all of the rooms I had in my original design, so two of the four bedrooms get partially extended out the front of the house, leaving a space in the middle for a tree where the front door is, which is then brought as-if into the vaulted space by a whole ton load of glazing:
(If you’re wondering why there is a transparent house next door, it’s because the site next to us is empty. The white houses are existing neighbour houses)
To then round out the protruding bedrooms, we run a cage around the house to encompass the patio outside the living room:
You no doubt notice the greenhouse at the back – myself and Megan are keen on growing a fair proportion of our annual fruit and vegetables, so we have a full house length three metre wide lean to greenhouse. The house’s exhaust air from the MVHR vents into this greenhouse, filling it with extra CO2 and moisture, but also constantly ventilating it. You can see a full house width of raised tanks above the patio, these actually sit above part of the master bedroom and living room – they harvest rainwater from the roof for the greenhouse. It should be possible to store 8000 litres up there, with additional harvesting tanks for the greenhouse as the wind dominates from the south west, and thus it is the south and west faces which receive the most rainfall.
However that large greenhouse comes with a big cost: no direct glazing on the south side of the house, because where the greenhouse joins the house it must be wall. Equally though there is a big benefit: the extensive groundfloor glazing is almost entirely blocked in summer by all those plants, but for the rest of the year it permits significant solar ingress, as is obvious from the sunshine falling through in March. That means solar heating for eight months of the year, but no overheating in summer.
Finally, let’s look at my proposed back garden and the enormous thermal store I want (as explained in in my original post in August):
You may have noticed that the site is actually two sites joined together, yet even with the 0.35 acres that affords, there isn’t really that much of a back garden. The brown walled patch is a walled garden for growing things perfectly happy outdoors and for which valuable greenhouse space is a waste – potatoes and carrots are excellent examples, they grow even better outside than in a greenhouse. That leaves not a massive garden once everything else is considered. It’ll do, but given all the money I spent on two rather than one sites, it does feel a little underwhelming. At least it’ll keep the mowing effort down I suppose.
(Indeed, the most likely reason we think this planning proposal will be rejected is ‘inefficient use of serviced sites’ i.e. we used two serviced sites for one house, which therefore deprives others of a potential house. Never mind how pokey small those sites are!)
Finally, witness my thermal store! It’s really massive. It dominates the utility/plant room. To the left of it will be the MVHR and any heat pump if it turns out we need one of those (we currently think that as a passive house, a heat pump won’t have cost benefit). The remainder will be washing and drying machines. But just look at how big that thermal store is, it’s 2m wide x 2m deep x 3m high including lots of insulation! Contains 5000 litres of water storing approximately 200 kWh of hot water. With the insulation I have planned, it should leak around 40 watts of heat into the house, so about one third of a human adult being in the house i.e. eminently tolerable.
As described in that earlier post, the thermal store gets heated by any excess left over from the solar array on any sunny days. As it’s so massive, and passive houses need so little energy, that thermal store if completely full is enough to provide domestic hot water and space heating in winter for around a week in a worst case scenario e.g. Beast from the East outside temperatures with mains electricity off for the entire week. In normal scenarios, it should be able to carry the energy gathered from a few sunny days in winter for up to a month, thus offsetting the need to top up the thermal store using cheap night time electricity.
It’s a very simple system, albeit highly unconventional when almost everybody else would just fit a heat pump. However my maths says that oversizing this tank only costs a bit more than a grand more, whereas a heat pump costs at least eight grand including commissioning. Sure, the heat pump might deliver up to 5 kWh of heating for 1 kWh of electricity, but because it requires periodic expensive servicing and probable replacement after fifteen years or so, and you really don’t need much heating for a passive house which reduces the return on investment, if you work it out it makes more sense to oversize the tank and solar panels and use cheap nighttime electricity to charge the tank if needed. Also in favour of this is that a heat pump can always be fitted later (ideally when they’ve become cheaper), whereas a tank this large has to be designed in from the beginning.
Anyway this is the design being submitted to preplanning this week. We shall see how it goes!
Incidentally, so later makes sense, we intend to meet the RIBA 2025 challenge for this house:
|Irish 2019 NZEB BER A1 House||German Passive House Classic||RIBA 2025 Challenge|
|Heat & Ventilation Energy||≤ 25 kWh/m2/yr||≤ 15 kWh/m2/yr (40% better)|
|Air Leakage||≤ 3 m3/hr/m2||≤ 0.6 air changes per hour (72% better)|
|Wall & Floor Insulation||≤ 0.18 W/m2K||≤ 0.15 W/m2K (17% better)|
|Window Insulation||≤ 1.4 W/m2K||≤ 0.8 W/m2K (43% better)|
|Total Energy Use||≤ 120 kWh/m2/yr||≤ 60 kWh/m2/yr (50% better)||≤ 60 kWh/m2/yr (50% better)|
|Embodied lifecycle carbon emissions||≤ 1200 kg CO2e/m2||≤ 800 kg CO2e/m2 (33% better)|
|Potable water consumption||≤ 125 litres per occupant per day||≤ 95 litres per occupant per day (24% better)|
|Indoor CO2 levels||≤ 900 ppm|
|Indoor VOC levels||≤ 0.3 mg/m3|
Getting from my original design to this final design
Once it became obvious that Stephen’s design was much superior to my original (hardly surprising!), we dropped my design and focused on bringing into his the essential features we wanted.
Poor Stephen had to work very hard these past few weeks. Our initial round of feedback took me three hours to type out and it was pages and pages of text. As he modified things to meet our feedback, the amount I had to write each round of feedback iteration kept shrinking until it reached zero. There was also quite a fair bit of teaching, as what I’ve designed here is non-standard, and I needed to explain why what I wanted was sensible, or indeed how it even works at all. Because it’s an overall systems based design, everything relies on everything else to make sense, no single item makes sense on its own. Stephen in fairness to him kept plugging at it until we got over the line this past week.
Stephen has taken the Passive House Institute’s design course, but this will be his first Passive House. To be honest, Passive House is a touch overkill for the mild Irish climate, most of the value is their PHPP software for modelling the house which is orders of magnitude better quality than the 2019 NZEB DEAP model. I can see most clients getting the most value from generating a high fidelity PHPP model rather than actually going for full Passive House certification, which greatly limits your construction choices whilst also adding on cost.
Most of the changes to the original concept were induced by the master bedroom. In VR, it was originally obviously too small, and purely to solve that we ended up extending the ground floor house length from 18m to 20m. In order to add in a porch to prevent heat loss when entering and exiting the building, we ended up having to rotate the master bedroom en suite to the middle of the house, and combined with the added two metres that made the master bedroom wide enough and long enough. However in terms of compromise over our original design brief, it has been the master bedroom which has taken the brunt of things. Stephen very much wanted us to move the master bedroom upstairs where there was a lot more design freedom, so in the end we had to choose compromise if we were to stay on the ground floor.
The other significant design change was to raise the mezzanine upwards in order to form storage for the games room next door, but also to raise the reading and library area further away from the living space so it is more separated and peaceful.
Estimated materials cost of this final design
One can fairly easily estimate house shell areas from the plans: Total wall area: 301 m2; Total roof area: 285 m2; Total floor area: 181 m2; Total wall glazing area: 61 m2; Total roof glazing area: 9 m2. Total indoor volume: 1243 m3. Total living floor space: 269 m2.
Straight away from those one can calculate:
- Heat Loss Form Factor (HLFF): 3.11
- Surface to Volume Ration (SVR): 0.674
- Glazing as a percentage of footprint: 39%
- Percentage of roof is flat: 31%
A passive house aims to get HLFF below 3.0 and SVR below 0.8. As you can see, we achieve the latter but not the former thanks to the vaulted ceiling taking away a good deal of floor space, which hurts HLFF. SVR is well below 0.8 however, so the design is ‘compact’ relative to the typical Irish build which is around 1.0. Unfortunately energy requirements are per m2 of living floor space, so as you can see this vaulted ceiling will hurt us.
If one estimates the following materials costs inc VAT: Wall 0.15 W/m2K €250 per m2; Floor 0.11 W/m2K €100 per m2; Roof 0.13 W/m2K €300 per m2; Wall glazing 0.8 W/m2K €700 per m2; Roof glazing 0.7 W/m2K including mechanical external shutter €1,550 per m2, then we arrive at a materials cost estimate of €239,571 inc VAT.
They say for a typical Irish house that materials are usually 40% of the final all-in bill, so that suggests a total build cost of almost exactly €600,000 inc VAT. That is about €200k more than I am able to raise in terms of finance, so I’m really hoping I’ve overestimated my costs here. Another common ratio for passive house builds is that passive house grade materials will be 55% of the final cost excluding professional fees because most builds are manufactured in a factory offsite and assembled onsite in under two weeks which significantly reduces onsite costs. If so that is €436k, which is still €50k more than I can raise. I guess we shall see!
Estimated energy efficiency of this final design
What I’m about to do next will be very inaccurate compared to a DEAP energy model let alone a PHPP energy model, but let’s take a guess at energy efficiency.
- There are 0.1 uncontrolled air changes per hour due to leakage, which for the above indoor volume is an uncontrolled ventilation rate of 124 m3/hr.
- The indoor temperature is 21 C and the outdoor winter and summer temperatures are 2C and 15C respectively.
Then assuming air carries 0.33 W/m3K of energy and the component W/m2K listed above, the shell heat loss in winter would be -3.763 kW and in summer it would be -1.188 kW. Note the lack of time in those numbers: we are saying that if inside is 21 C and outside is either 2 C or 15 C, then that is how much heat is leaked from inside to outside by the shell materials and air leaking through the shell (note that 0.1 ACH for a passive house which cannot exceed 0.6 ACH in a hurricane would be quite a windy day, however don’t forget people opening and shutting doors).
Let’s go a bit further by assuming:
- The MVHR unit has a heat recovery efficiency of 80%.
- It runs at 150 m3/hr.
Then we can calculate that the heat loss due to intentional ventilation will be -0.188 kW in winter and -0.297 kW in summer. That might seem surprising – the reason why is that the MVHR in summer will be in bypass mode i.e. not heat recovering.
Let’s go even further by calculating heat gain from solar radiation. According to the PGIS database for our site location:
- In winter 50 kWh/m2/month lands on the roof, and 10 kWh/m2 will land on a vertical window. As there are 730 hours in a month, and glazing might retain 50% of the heat entering the house, this is 0.034 kW/m2 and 0.007 kW/m2 respectively.
- In summer 140 kWh/m2/month lands on the roof, and 80 kWh/m2/month will land on a vertical window. This is 0.096 kW/m2 and 0.055 kW/m2 respectively.
Applying this to my glazing:
- In winter, the roof and wall glazing would add 0.724 kW to the house.
- In summer, with the external shutters covering the roof glazing and plants in the greenhouse covering half of the ground floor southern glazing, the wall glazing would add 1.19 kW to the house.
What remains now is how much heat the house generates from being lived in. I can tell you that for my current two storey 60 m2 rented house, between cooking and various devices using electricity, we consume 0.534 kW, which excludes showers or heating. Add in five human adults’ body heat 0.38 kW and five 75 litre showers per day with wastewater heat recovery @ 75% = 0.182 kW, I reckon there is a minimum baseline heat generation of 1.096 kW, which may be an underestimate given just how much illumination I plan to fit to this future house.
If you now tot up this baseline internal heat generation with the solar heat gained by the glazing, the shell heat loss, and the ventilation heat loss, you get:
- In winter, there is a negative 2.13 kW.
- In summer, there is a positive 0.802 kW.
Or, put another way, in winter we must add 2.13 kW, and in summer we must remove 0.802 kW, to keep the house at 21 C.
You now may understand why I intend to fit an earth tube which I reckon will subtract -0.97 kW in summer, thus turning an overheat into a negative 0.168 kW. Most will point out that a heat pump can just as easily run in cooling as in heating, however note that my cooling here comes completely free of electricity cost, it’s just the considerable capital cost of installing an earth tube here (they cost only a bit less than a heat pump, though as a dumb pipe in the ground their service life well exceeds my lifetime).
It’s an interesting question whether a thermal store + earth tube + wastewater heat recovery will beat a heat pump. I think it will, which is why I chose this design, but for a BER A1 Irish house, because it uses twice as much energy, a heat pump really does make sense as its return on investment is much better. A heat pump does deliver up to five free kWh for every one kWh of electricity used, however a thermal store lets you capture all those occasional sunny days you get even in winter in Ireland, and an earth tube lets you cool your house without any electrical cost at all. Wastewater heat recovery means long showers aren’t dumping energy down the drain. So once you factor in how hideously expensive periodically topping up the refrigerant gas in a heat pump is vs the added expense on night rate electricity, and given a thermal store + earth tube + wastewater heat recovery unit has identical capital cost to a heat pump, I reckon they’ll come out pretty close in terms of total lifetime financial cost.
Indeed, from a passive house calculation perspective, the heat pump is definitely preferable because its embodied carbon cost (which is very significant) isn’t included, nor is the fact its refrigerant gas which slowly leaks out is a known climate warming gas. This is why the RIBA challenge is important – it makes you consider that exchanging improved energy efficiency for much worse impact on the planet is not a good deal.
Note in all of the above that our site is unusual for Ireland in that having two river deltas to either side makes an earth tube unusually effective, most sites in Ireland would see nothing like as much benefit from an earth tube. This made my choice here much easier than it would be for most other sites.
Note also that wastewater heat recovery makes sense only in a passive house where domestic hot water consumption is a large proportion of the total annual energy consumption. In an Irish BER A1 house, you effectively get hot water as a side benefit from the heat pump. It’s a different set of tradeoffs.
Estimated annual bills for this final design
Firstly, 31% of the roof being flat puts a fairly heavy loading on home insurance. One might expect to pay 40% more annually, maybe +€160 a year.
The baseline electricity load is what it is, including standing charge of €300 and assuming more of it lands in the expensive daytime rate (€0.25/kWh daytime vs €0.10/kWh at night) I’d estimate the baseline electricity bill at €1,118 inc VAT per year.
If it were winter constantly for three months of the year i.e. 2C throughout, and no space heating were needed for the rest of the year, and solar diversion from occasional sunny days supplemented 20% of the space heating during that time, I’d estimate the electricity needed for space heating charged at night time rates to cost €501. This gives an estimated annual bill of €1,619 inc VAT.
To put this into perspective, for my current two storey 60 m2 rented house I spend €840 a year on electricity and about the same again on kerosene for space heating, which is about 11,500 kWh in total giving 192 kWh/m2/yr which is a BER C2 rating, and I can absolutely guarantee you that the indoor temperature is nowhere near 21 C in winter e.g. as I type this right now at 3am it is 18 C in this room. This, incidentally, includes a solar domestic hot water collector which they say reduces your annual heating bill by 10-15%, without that this house might be BER D1 rated.
Can this design be passive house certified?
If any of the estimates above are anywhere close to correct, primary energy demand for the proposed house would be around 11,000 kWh, almost the same as for my current rented house. However, this is for 260 m2 of living space instead of 60 m2, which gives a 41 kWh/m2/yr which is well below the limit of 60 kWh/m2/yr required for Passive House Classic, and is even below the 45 kWh/m2/yr limit required for Passive House Plus.
That no doubt it an underestimate. If preplanning smiles on this proposed design, I look forward to seeing what PHPP returns for this house and how it compares to my very rough workings above!