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, especially in terms of broken links or images.
- 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???
Latest entries: 
The neighbour was to install 24 metres of the 34 metre length at their expense, and I was to complete the other 10 metres at my expense. This may sound unfair, however my portion was the earth retaining portion and the quotes which came in before we decided this were about equal if we paid others to do it for us. I elected to use these ‘lego’ concrete blocks and install the wall myself instead of paying others, and thus saving myself about six thousand euro.
The neighbour’s contractor had installed the poles for his fence, but left them unfilled so I knew exactly what height my blocks had to reach in order to be flush.
Firstly, I dug a trench using the 90 cm wide bucket down to 240 cm below the top of their fence pole:
This usefully revealed subsoil, which isn’t noticeable from the photo for some reason. But when you’re there in person, the subsoil is a distinctly different colour from the topsoil, kinda rusty coloured brown instead of darker brown. The different colour really shouts out, you couldn’t miss it if you were there in person.
As I was on my own, I couldn’t use a thwacker which is a machine for pounding surfaces hard as it requires two people, so I had to resort to the tool used for at least five thousand years – a tamper. This is quite literally a heavy flat sheet on the end of a stick. You repeatedly whack the ground with it to pound the surface. It is very considerably more effort than the machine, but I can do it alone, and well it’s like an extended gym session, it’s highly fitness inducing.
Anyway, after tamping the subsoil flat and ensuring it was level in all directions using a level meter, I then poured a few wheelbarrows of two inch down crushed rock, got those level, and tamped those hard too:
Now I could drop in the blocks on a perfectly level, well supported base:
As you can see, I have at the end a support column which cantilevers support into the next ten metre run of the wall. For a normal cavity block wall two metres high, you’d have a support column every five meters or so. The reason that we can get away with one support column every ten metres here is the sheer mass of these blocks making them much more effective at pinning lateral forces, but also the width of the blocks being two thirds of a metre and more than easily wide enough to walk along. You can give this wall a good hard shove from the digger and it realigns, but it does not tumble. And that’s a six tonne digger I was shoving it with!
After that came lots more soil levelling, tamping, crushed rock layering, more tamping. I didn’t do the majority of this, Megan did the bulk whilst I shovelled crushed rock into the wheelbarrow and brought it to her. We had in fairness spectacular weather, only once in every three or four years do you get consecutive back to back sunny days in Ireland for multiple weeks. We were extremely fortunate to be doing this work in one of those rare extended sunny periods for Ireland.
It took two full days of work to lay the bottommost layer of blocks due to all the finicketyness. Laying the next two rows was done in mere hours:
All that attention to detail about ensuring everything was level and firm in the foundation shows its payoff by all the blocks neatly packing together tightly without gaps. If the right side looks unsupported, note that just behind it is a packed earthern mound support made by me with the tamper – you pour in soil recently excavated, and tamp it until it forms the same earthern mound shape at the back of the neighbour’s property. This supports the blocks from the neighbour’s side right up to the third layer of blocks.
Total cost of this was €68.10 inc VAT per block delivered X 24 plus 2 X €385 for six tonne digger rental and its diesel = €2,404 inc VAT. Compared to the quote we got for over eight grand … this has been quite the saving. What we gave up was our time (three days, arguably five if including the sorting and moving these blocks to where they would be used!), and the additional space consumed by the size of the blocks which eats out of our garden.
Equally, you are looking at the first quarter of our future walled garden where in the future a fair chunk of our food calories shall be derived! I expect to mainly grow potatoes and carrots in this walled garden. It will be exactly square, so the 8.4 metre inside you are currently looking at will become 70 m2 of walled garden growing space.
Assuming the typical ten tonnes of potato per acre yield in Ireland, that equals about 172 kg of potatoes per year. Less if also growing carrots, which would yield 112 kg if using the entire walled garden.
To put that in perspective, the average 2023 Irish person would consume about 60 kg in a year, mostly in the form of fries. I chose 70 m2 because it would roughly approximate half the annual potato consumption of five adults, so with carrots and maybe peas thrown in, that’s about one quarter. The idea is that if all our children flee us in years to come, we will rarely have surplus to needs. But if they end up staying because they’ll never be able to afford their own homes as I expect will be the case, then we get a substantial subsidy to our annual food needs.
And also: there is zero comparison between shop bought food and the stuff you grow locally. Our potatoes, carrots and especially peas will be amazingly tasty in a way you can’t get from supermarkets. So there is a qualitative aspect in there too.
Anyway, I’ll leave you with a wide view photo of the whole boundary fence between our site and the neighbour’s, taken in sunshine just before we departed to get Chinese takeaway:
Raw data: http://www.nedprod.com/studystuff/SSDsVsHardDrives.xlsx
This time last year I predicted:
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
This time last year I thought a recession would be upon us by now, as interest rates rose above inflation in order to bring it down. I still think that will happen, it just hasn’t happened yet – interest rates are indeed many times higher than last year, but inflation hasn’t really dropped by much. So either there will be recession sooner rather than later, or interest rates will have to rise some more. In any case, a recession.
I won’t predict that for this time next year, as clearly I suck at timing. Let’s look at the new numbers. Well, the big stand out thing is that Optane storage lept forwards in capacity per inflation adjusted dollar. Like so much so that it nearly entirely eliminated how much it fell behind flash storage, so now it’s nearly tracking flash storage improvements. Who knew that Intel disposing of Optane would lead to such price reductions for that technology? Here’s hoping that only improves much further still.
Flash storage saw a better than trend improvement, whilst spinning rust stayed on trend. Do you know something interesting? Flash has nearly returned to an intersection path with spinning rust for the first time since 2012! That’s kinda exciting, back in 2012 flash storage was still in its linear improvement stage, had that continued it would have overtaken and completely replaced spinning rust by 2018. Obviously the linear growth turned into exponential decrease, however with these most recent numbers the regression predicts both trends go parallel (and very close, though without crossing) from 2050 onwards.
I personally think that unlikely, you can’t eek out that amount of density from silicon, nor the cobalt based magnetic alloys of hard driver platters. So at some point well before then, I would expect both to stop improving and plateau absolutely.
The question is which will be first? My money is on silicon plateuing first. Spinning rust has been around in one form or another since the 1950s, yet improvements in data storage density have been sustained since then. Whereas silicon based storage density started much later, but saw much steeper improvements so it caught up. I still think it is a ‘flash in the pan’ compared to spinning rust, and it’ll peter out first.
Hard to predict however – much of why spinning rust can now achieve such data densities is due to sticking what was a mainframe a few decades ago onto each hard drive to crunch the maths necessary to pack data so densely. So both technologies are actually in lockstep, and if silicon stops improving, that’ll impact spinning rust as well.
I’m sure you remember the GARE, the Ground-Air Heat Exchanger which was a 46m length of 200mm diameter buried pipe through which the air intake for the house flowed, thus cooling it in summer and heating it in winter? Well, it’s been ditched, I just couldn’t justify its cost for its benefits. Getting the pipes from Germany to Ireland was quoting at €8,100 or so, and certainly a further €3k to install them. I tried getting cheaper pipe, HDPE which is best material for conductivity requires a specialist contractor to fuse them, and thicker PVC pipe which only requires solvant glue to fuse I would have had to laid two parallel runs to achieve the same efficiency, so once again, back towards the 8k + 3k cost.
Ground-water heat pumps would be the next obvious alternative, these being what most people think of as ‘geothermal’. These work via a buried hose about 1.5m deep through which runs brine water. The heat pump exchanges heat between the inside and the outside buried loop in either direction. These were somewhat popular 10-15 years ago, but as air-water heat pumps became de facto obligatory in new builds in the EU after 2019, the ground-water heat pumps have become difficult to purchase, plus they have risen in price along with recent build inflation. I reckon you’re talking €20k for one now, and another €5k to install it because they require a specialist design team to prevent them freeze locking.
I could just bite the bullet on an air-water heat pump, though they’re costing €15k or so nowadays including installation. But then I discovered that Zehnder have launched two add-ons for their ComfoAir Q range of MVHR ventilation units:
For €6,200 inc VAT one can get the Zehnder ComfoClime 36 which is an air-air heat pump able to cool up to 1.7 kW and heat up to 2.2 kW at COPs of 3.0 and 2.5 respectively. No external fan unit needed, which is nice, but it would dump extra hot air into the greenhouse in summer.
For €5,450 inc VAT one can get the Zehnder ComfoFond-L Q ST which is an air-ground heat exchanger needing lots of metres of buried PE pipe 32.26.2 dimensions. It only draws 70 watts maximum so clearly cannot be a heat pump. It has no performance data, however it surely would be as efficient as the GAHE, and is obviously cheaper.
Of those two, obviously I’m rather liking the ComfoFond as it slots right in instead of the GAHE. Maximum possible cooling remains the same as this is the heat capacity of air: if outdoor air is 25 C, and below ground is 10 C, then:
- 350 m3/hr is 1.75 kW of cooling.
- 450 m3/hr is 2.25 kW of cooling.
- 600 m3/hr is 3 kW of cooling.
Actual cooling will be less than that, but you don’t need much to drop a passive house internals by 1-2 C.
What’s nice about this not being a heat pump is that any old joe can install the buried loop i.e. me, because the coldest brine you’ll ever send down there is the outdoor air temperature, and via anti-freeze you can abaolutely guarantee it’ll never ever freeze. This makes the pipe design very simple, no T-branches needed to spread a freeze load across trenches, you can use a single straight run of pipe which further reduces the chance of later leaks etc. 150 metres of pipe is around €180, and trenching it with a digger is well within my abilities. As you’ll only be putting 3 kW through it, 150 metres ought to be plenty.
I had been budgeting €20k for the site prep and GAHE installation, I think that has now been reduced to €7k if I install the loop myself. This is good, as I suspect the M&E design costs are going to well exceed the €10k I allocated for them, but more on that in another post.
I reckoned that my company whose office is on the site would be justified in purchasing security flood lighting, so I picked up two 200 watt LED flood lights. That’s not 200 watt incandescent equivalent, that’s 200 watts of electricity consumption. They are unsurprisingly therefore rather bright:
Using a wattmeter I verified that it does indeed draw 200 watts. Once warmed up enough, that does drop to 193 watts, but that’s the physics of LEDs for you.
So just how much light is there? Remember my cove lighting? It outputs plenty enough light with which to read comfortably in a nice even spread. According to my phone sensor, it reads 105 lux from the couch which is maybe 1.5 metres from the roof, with the light reflecting down. With the floodlight pointing straight up and a box hiding it from direct glare, the phone sensor reads 750 lux just from reflected roof light alone. I’m strongly considering fitting these into the vaulted space in the house as uplighting, a few of them together would be pretty decent and even coverage, and if you vary the colour temperature between them then the CRI won’t be half bad either.
The unit claims 22,000 lumen, but I have no way of testing it other than what I’ve done. I can say that my workplace high lumen lighting solution which keeps me awake and working productively late into each night:
… emits 806 lumen x 5 = 4,000 lumen, and my phone’s sensor reads 400 lux when about 1.8 metres away with the phone pointing at the light. So to get nearly twice that after a 2.5 metre travel and a reflection suggests the floodlight may be telling close to the truth – it helps trust that the units appear to be manufactured in Britain, and not in China. They’re also very well made, with big hefty heat sinks on the back which do a great job of drawing heat away from everywhere else. I left it run for half an hour, then took these thermal images, firstly of the front and then the back:
(In case you’re wondering, yes my Hikmicro thermal camera finally got a firmware upgrade which retains the visual camera image. Turns out said camera is dog shit bad and the images are saved with severe JPEG compression, but it’s much better than nothing)
As you can see, the front remains under 50 C with only the outer frame conducting heat from the back. The back meanwhile, well it gets up to 70 C or so. This is good thermal design, I also had it on its back so the heat would rise, if it were facing down like its designers intended it would be still cooler again.
Anyway, these particular units are destined for poles raised high over the site. Just need to get the mains electricity activated – it was paid for 11th April, so nearly seven weeks ago now. Here’s hoping they get round to it soon!
Firstly, this is what they look like, this is the pile dropped at the front of the site:
They may look uninteresting at first glance, but they have some interesting characteristics. They are 1.4 tonnes in weight each, 1.4m long, 0.7m high and 0.68m wide. ‘That’s a weird width?’ I hear you ask? It’s explained by the volume: 1.4 x 0.7 x 0.68 = 0.666, or exactly two thirds of a m3. I paid €68.10 inc VAT and delivery for each of them. That makes them €102 inc VAT per m3, when ready mixed concrete is currently costing north of €140 inc VAT per m3 depending on delivery quantity. This makes them rather good value!
Most other suppliers were looking for €100-140 per block delivered, only one was looking for around €90. So I lucked out in finding a supplier keen to turn inventory into cash before the surely soon building downturn.
Pricing them higher than ready mix is somewhat disingenous of the sellers of these blocks however. They’re actually made from the leftovers in the ready mix trucks when they return to base due to a customer ordering more than they needed, so the concrete was already paid for once. Sure, the galvanised steel reinforcement frame which also provides a lifting loop might cost maybe €30, and the casts will cost a few bob, however I think these are likely quite profitable at over a hundred euro per block. At €68, well, I suspect he wasn’t making much profit if his input costs are what they are now – however chances are he was churning out those blocks over the past few years, and most of them were made back when concrete was a lot cheaper. In any case, they are vastly cheaper than a concrete block wall, never mind an earth retaining wall. They are bulky however, so you swap space consumed for reduced price.
Luckily due to having two merged sites I have the space to swap for reduced costs, so that works for me. Using the digger, I firstly sorted the blocks into ‘ugly’ and ‘pretty’, where ‘ugly’ is defined as blocks with chips in their sides and ‘pretty’ are blocks without chips in their sides (though they can have them at their ends). The ‘pretty’ blocks will be exposed to view permanently, so I want to be looking at a smooth-ish surface. The ‘ugly’ ones will be behind retained earth, so I’ll never see them.
I stacked the ‘pretty’ blocks in a newly cleared rear space I created with the digger, which puts them next to where they’ll be used after my neighbour finishes his part of the boundary fence.
You may be able to notice that the blocks at the back left the third row is sloppy. Those were my first ever attempts to get the digger to raise the blocks that high, and there is a skill to it because the digger really doesn’t like lifting 1.4 tonnes that high. By the time I got to doing the columns on the right however I had it down to a fine art, if I do say so myself. Each of those columns in 2.1m high, and I made sure when climbing over them that I could not cause anything to move nor relocate with all my adult strength. I can’t stop the local children climbing on them, but they definitely will never be crushed by a falling block, those blocks are extremely secure.
To lift the blocks one needs a 16 mm diameter shackle rated for two tonnes to fit the lifting loop in each block. I bought these from Amazon for an absurdly low price:
About £50 for all those shackles. Madness. Are they any good however? Well I did do my research, those are Titan Marine shackles, the low end (yellow) not high end (black) ones. They are made in China with the original Canadian manufacturer having been bought out by a Chinese company, and Practical Sailor’s 2015 review of anchor shackles found them absurdly better than rated specification in their empirical testing, they broke at 43% more load than their rating. Interestingly, the yellow ones performed identically to their black ones, yet cost a fraction of the price. One suspects that they are actually the exact same shackle, just with two pricing strata (alas, the black ones claim to be 67% stronger than the yellow, so snapping at 43% more means they fail their claimed specification).
Having been very mean to those shackles over three days, I can confirm that they did not even remotely deform nor bend nor even jam their pins. They absolutely breezed through what I put them through. This suggests that they are indeed very very strong. They did, annoyingly, produce a lot of metal slivers from grinding which become splinters in your hands. Most painful, and much tweezering was needed each night (I couldn’t use gloves, as I couldn’t screw or unscrew the shackle in the limited space with gloves on).
Whilst the ‘pretty’ blocks went into those columns, the ‘ugly’ blocks went to seal the back corner of my site where the western wall stops early – there is about a 3.5 metre gap there through which anybody could drive anything. I had been concerned for some time that that was the obvious place to steal building materials, so blocking it off securely was desirable. Let’s see anybody get through this in a hurry:
This is actually temporary, I didn’t have the time to do better last weekend. Some other weekend I’ll rent that digger again and redo that bit properly – I need to lay crushed rock foundations, compact that down to a firm flat layer, then lay the blocks straight with a connected L-shaped earth retaining wall. There will be a 1.4m wide space between that outer wall and the earth retaining wall, that is for plant and pumps and it’ll be mostly covered from the elements to keep the rain off it. This will make use of a spare roofing metal sheet which Irish rollforming threw into my order unexpectedly for free.
Getting that done will be a while away. Completing the neighbour’s boundary wall will be higher priority, but I’m blocked on his contractors for that.
Anyway, I have to admit these ‘lego’ concrete blocks have been a real joy to use. They’re easy to move around and lay with just me alone, unlike a lot of other building techniques. They’re a touch ugly true, but they’re vastly cheaper than labour doing a concrete block wall or especially retaining wall. They also make a most satisfying ‘clunk’ noise when you drop them in. And what adult doesn’t want to build stuff from grown up Lego blocks?
The big movement since the previous post on my future house build is that the AIB came back with a mortgage offer – apparently they’d issued it prior to the last post here, but it had gotten lost, only when I went asking about progress did they find it. Their Approval in Principle was for 3.25x income i.e. LTI ratio of 3.25x, where the legal cap is 4.0x for first time buyers like me. That would normally be a problem for most people (effectively it’s a ‘soft no’), however in my unusual case due to the remote rural location the valuation was always going to be the limiting factor, and we had never had any illusion about that from the very beginning. To remind people of the post from February, mortgage lending maximums are:
No more than four times your average income in the past three years (this is the Loan to Income limit set by the Irish government).
No more than the cost of construction (€700k).
No more than 90% of the final valuation of the completed property.
So everything was always going to hang around the valuation. The AIB ended up appointing Liam Mullins & Co estate agents as the valuators, they are the most successful of the local regional estate agents. In fairness to them, they did take their time to understand the build detail, the design detail which surprised me. They then surprised me even further with a €490k valuation, which seems rather high for the area!
Let’s compare that to other recent sales in the same estate. Price data is from https://www.propertypriceregister.ie/, the rest I culled from estate agent listings, the plans on the public planning applications website, and the CSO data for house price inflation in the P51 eircode district.
2023-02-14: 24 Ard Na Si, €390k.
- Four bedrooms, four bathrooms, BER B2, 316 m2, built 2009. €1,234 per sqm.
2022-05-08: 36 Ard Na Si, €265k.
- Three bedrooms, BER C2, 151 m2, built 2009. €1,755 per sqm (normalised to 2023 prices: €1,562).
2021-12-06: 32 Ard Na Si, €300k.
- Five bedrooms, 260 m2, built 2007. €1,153 per sqm (normalised to 2023 prices: €1,191).
2020-10-30: 2 Ard Na Si, €218k.
- Four bedrooms, built 2012. Not more than 160 m2, if so around €1,363 per sqm (normalised to 2023 prices: €1,644).
You’ll note the unusual price per sqm distribution peculiar to British and Irish house prices – we are unusual in the world by not following a universal price per sqm for a region which most of elsewhere does. Instead we price the first 120 m2 of any quality (no matter how bad) at an eye watering price barely affected by quality nor condition, then remaining m2 especially cheaply but with more account of quality and condition. This is due to the bimodal nature of house buyers in Ireland and the UK – there are lots of people who will take any house at all, and they tend to overly bid up the bottom end of the market which rather does a disservice to the non-wealthy (in any other country, they would live in high density apartments and would never consider owning a house, but that isn’t the culture in Ireland and Britain). Meanwhile, those who can afford to pay a little bit more get far less competition during bidding, and so can be more picky. It also means they (relatively speaking) get bargain housing in terms of additional space and quality/condition per euro spent.
You can see this in the above where there are two categories of house on the estate: let’s call them ‘premium’ and ‘non-premium’ (the plot sizes are all identical, so only the house affects the sale price). In 2023 adjusted prices, premium houses sell for ~€1,200 per m2 and non-premium sell for ~€1,600 per m2, a 25% discount per m2, but premium houses have at least 75% more floor space and so therefore cost more overall. Or, put another way, ‘non-premium’ housing is around one third more expensive per unit of living space than ‘premium’.
Having explained all that context, doesn’t the €1,570 per m2 valuation for my house (which is ‘premium’) look excessive? The CSO stats reveal something interesting: between 2012 and 2018 new house sale prices had a ~15% premium over those of used house sales, which would be a percentage consistently repeated anywhere in the western world historically speaking, as people do like brand new over used; however from 2019 onwards the new house price premium rose to a fairly astonishing ~75%, at least for the P51 eircode region.
Changing the eircode region reveals that the same phenomenon appears countrywide, but with different start dates. Cork southside is like the Mallow region, the new build premium jumps around 2019. Cork northside saw it jump from 2016; Naas saw it jump from 2015; Dublin 24 (south west) appears to have gained the premium as early as 2011, albeit consistently lower over time at ‘merely’ ~48%.
As to likely causes, I must admit to being a bit stumped. Significant first time buyer subsidies only came in from 2017 onwards, and they cannot explain more than 5-10% of the premium in any case. Britain has similar weird patterns in new build price premiums with a clear pattern of the highest premiums being in the historically least developed areas, same as what we’ve observed in Ireland above. The evidence is clear that the new build premium vanishes after about three years, so that’s effectively negative equity of 50-70% in year three unless house prices are generally rising, which is motor car type value depreciation. I’m going to have to put it down to the same phenomenon as with motor cars: humans are irrational about ‘new’, and the irrationality is particularly pronounced with what is deemed a premium brand or thing which isn’t really all that much better than the non-premium brand or thing, but people simply go nuts on them. A five year old motor car rationally speaking ought to be worth most of a brand new motor car – it’ll be barely more efficient, and wear and tear replacement parts won’t cost much for years yet to come. Yet motor cars consistently lose half their brand new purchase price after three years, and that’s been the case since the 1960s at least. Similarly, a five year old house ought to cost most of what a brand new house costs, very little would need replacing or maintaining. Yet, apparently irrationality says otherwise, as clearly Akerlof’s Lemons effect couldn’t rationally generate such large price premiums.
I assume that the estate agent’s valuation is meant to be for after three years not new, so on that basis they were rather generous to me in the valuation – they used the non-premium per m2 value rather than the premium value. Equally, if the bank seized the house when it were still new, it would be worth far more due to that new build premium. On that basis, the valuation was generous to me but fair to the bank. It’s not an unrealistic valuation.
Anyway, bringing all this back to my actual build, 90% of €490k =
€441k, which will cost me €2,700 per month in mortgage payments
to repay incidentally 
.
€700k - €441k = €259k as being the unborrowed cash sum that
we need to raise before September when the mortgage offer expires.
I don’t know if we can achieve that by then. Maybe. If not, we’ll
do all this again this time next year. As mentioned before, one is in
a terrible bind here – if I spend money on progressing the build,
I reduce the cash balance needed to get the mortgage, but if I don’t
spend money on progressing the build, I delay the build. And certain
things can only happen in the summer, when the ground is dry
.
This weekend is a long weekend, I have rented a six tonne digger with which to move a bunch of soil and relocate those lego concrete blocks away from the front where they are in the way. I am just praying that the rain holds off unlike the last time I drove a digger on that site, it quickly turned into a mud bowl.
The Ground Air Heat Exchanger (the ‘GARE’)
The GARE is simply 40 metres of dumb 200 mm diameter plastic pipe buried in the ground. The idea is that the house MVHR air inlet draws fresh air through the GAHE before it enters the house, so fresh air is brought closer in temperature to several metres underground i.e. cooler in summer, and warmer in winter. The heat exchange efficiency of modern MVHRs is so good that the GARE makes very little difference in winter, so its main purpose is to provide cooling for the house in summer. My probably not very accurate maths reckon it should be worth about 1kW of cooling, which for a normal Irish house wouldn’t be worth much. However, for a Passive House we have much much better air tightness, so that 1kW of cooling goes much further.
GAREs are rarely installed in the UK or Ireland, and mainly for commercial. It is nearly unheard of to install them for a domestic building in this part of the world, despite their being popular enough elsewhere in Europe and north of Africa. This is because only around 15% of the land in Britain and Ireland is suitable due to the wrong soil type or wrong internal pressure, plus you need to have the right kind of site as well. I specifically chose my site as I reckoned it ought to be unusually suitable for a GARE.
The installation plan looks like this:
A top down view doesn’t convey everything going on there: the GAHE enters the house via an underground 315 mm diameter pipe 2.5m long standing vertically on its end underneath the house. Until the GAHE 200 mm pipe reaches this vertical pipe, it slopes downwards during its entire length, so condensate from warm humid air meeting cooler earth drips downwards. When the vertical 315 mm pipe is reached, the condensate pools at the bottom where a level activated pump removes it so it doesn’t induce mould.
About half of GAHEs fail within their first decade due to mould buildup caused by pooling of condensate along the pipe. This is mainly caused by incorrect installation, but also due to heavy construction vehicles putting pressure above which puts unanticipated kinks into the pipe. To prevent that happening here, as you can see I have taken the pipe immediately away from the building rather than looping it around the building’s foundations as would be more typical. We bring it up next to the drainage ditch, and run it the full length of that ditch. The idea is that the static pressure of rainfall upon the estate will cause a constant underground flow of water towards the ditch, thus refreshing the heat capacity of the soil surrounding the pipe. This is what I meant about needing the site to be right, the site is within a river basin and so has silty soil which has high thermal capacity, and we also have static pressure driving underground water flow underneath the site. Most sites in the UK and Ireland do not have both prerequisites for a GARE to work well.
The top of the 200 mm pipe enters the 315 mm pipe 1.8 meters below the house. Most GARE installations use a 1% slope, we however shall be using a 3% slope from the house to the ditch to prevent later kinks introducing condensate pooling. The brings the top of the pipe to 1.4m below the ground which is too high, so to account for that as you can see in the diagram we create a retained wall raised garden to increase the depth. It must be raised no less than 0.1 metres to keep the top of the GARE its minimum 1.5m below ground (and in reality, we’ll probably raise it 0.3-0.5 metres with well manured soil).
After the GARE turns right, its slope increases to 4% under the current plans. This raises it by 1.2 metres by the time it reaches the western air inlet. At this point its top is only 0.2 metres below ground, however we have all along the rear a 2.0 metre high earthen wall which is at least 3.0 metres thick at its base. This ensures that the pipe is never closer to the air than 1.5 metres right up to the inlet, which should maximise heat transfer. The quite steep 4% slope is to prevent kinks from dumping a 2.0 metre high packed earth wall on top of the pipe, it’s a lot of weight and more importantly, it’s permanent so the ground under the pipe will never get the opportunity to spring back.
If I do say so myself, this use for the excess soil on the site after the foundations are dug out is quite clever. There is an existing low earthern wall plus an old spill pile from somebody else’s house. Adding that with the expected soil removal for my house should fill that wall and leave about 20 m3 remaining. I plan to turn that into my ‘holy pool’ water feature some day in the far future when I get both free time and sufficient money to do it. Disposing of the soil costs about €70 per tonne/€140 per cubic metre, so it also saves me money if I make use of the excess soil instead of spending more money to have it taken away.
As great as all this may look, I have a big problem: the GARE pipes are made by Rehau who are a Swiss polymers manufacturer. And as I mentioned earlier, almost nobody in Ireland nor the UK uses these, so getting them delivered to Ireland is going to be a real pain. I got a quote from their Irish exclusive reseller for over €7k ex VAT delivered. I can get the same pipes in Germany from an online shop for under €4k ex VAT delivered to Germany and its neighbouring countries. There surely must be a way of getting them from there to here for under €3k, even surely me driving a van there via ferry and back would be cheaper than €3k.
The longest pipes are 6 metre lengths which is problematic for pallet based freight, which maxes out at the 2.4m pallet. I could drop to 3 metre or 1 metre lengths, but that very substantially increases the cost per metre from €56 to €84. I guess I can try my luck on https://www.shiply.com/ or equivalents assuming that the German online shop is willing, it’s a light load at under 300 kg, just awkward that’s all.
The shed
Back last summer when I was ordering a garden wagon with extra large wheels to save me ever again moving concrete blocks one at a time by hand, I was looking on the vendor’s site for other things to buy for the fairly large delivery cost and I decided to also purchase one of their steel garden sheds. I originally intended to put it at the front, but then I realised that duplicated functionality already provided by the shipping container, so I then decided to put it at the back. However lots of other things were higher priority, so whilst I bought it in September 2022, I only got round to erecting it this month.
I spent a fair bit of time umming and awing on this one. If you want a quality steel shed, it is extremely hard to beat Britain’s Asgard who manufacture sheds. For the spec, I know of nothing remotely close in price – take their 7 x 7 ft model for about €2,000 inc VAT, it has 1.2 mm thick steel sheet walls and roof, comes with a built in metal floor (note this is rare in sheds!), and weighs 326 kg so it doesn’t even need anchoring to the ground for hurricanes. It would require a bit of effort to break into, more than a sledgehammer or screwdriver, an angle grinder would do it.
With hindsight, I probably should have got one of those, however what I got instead is a 225 x 225 cm (7.5 x 7.5 ft) pent shed from Sheds Direct Ireland for €754 inc VAT. In contrast to the quality permeating the Asgard shed above, this one has claimed 0.3 mm (I suspect actually 0.25 mm, see below) walls and roof with a 0.6 mm structural frame. It is screwed together by around four hundred screws, with all the screws easily accessible on the outside so anybody with a screwdriver can get inside. I found the OEM product listing at https://www.sunor.cn/product/Skylight-Metal-Shed/, with their Alibaba listing showing the cost for more than two hundred per order as US$140 each (which excludes shipping to Ireland and taxes), and also the weight as 68 kg per item.
Which is about one fifth the weight of the Asgard shed above (note that 1.2 mm divided by five is 0.24 mm, which is why I think the vendor’s claim of 0.3 mm thick panels unlikely), yet still two fifths the price once including the added costs: (i) I needed a heavy and raised base to keep the shed off the ground and away from rising damp plus to anchor it against hurricanes, which cost me €70 inc VAT for thirty-six solid concrete blocks (ii) I needed to level those blocks into a flat surface which cost a few dozen kg of sand (iii) €120 inc VAT for thirty concrete tiles to create a hard wearing floor, though arguably I’d have had to fit the same to the Asgard shed (iv) I had to buy a new long shackle lock costing €35 for it because its stupid door handles are too far apart for any of my existing padlocks (v) and finally, and perhaps the most important, is my very scarce and precious free time of which this Chinese shed consumed around three full days! Admittedly, this was spread out over many days these past two weeks, however I reckon about twenty-five hours went into prepping and constructing this thing. Which is very far from the claimed ‘two to three hours’ by its vendor …
As you might be gathering, there is a touch of buyer’s remorse here. I remember at the time of purchase I was very much thinking ‘either go quality or go cheap’ and I don’t particularly rate the 0.5 mm thick panels most of the ‘premium’ metal shed vendors in Ireland use. Sure, 0.5 mm is a world better than 0.25 mm panels, but do you know what’s world’s better again? > 1.0 mm panels. They actually have a good bit of solidity to them – not as good as the 2.0 mm panels on a shipping container for sure, but they don’t feel quite so ‘tinny’ any more. Whereas 0.5 mm panels definitely feel tinny – indeed, when I bought the one metal box roof panel for the western wall, I opted for the 0.7 mm panel for a little added cost rather than the 0.5 mm panel which most go for. That extra heft I certainly noticed lifting the damn thing, but I’m also very confident it will never rust through before I am dead, and therefore I will never ever have to redo that roof before I die. When you tap it, the panel ‘rings’ like a bell, which isn’t tinny.
My new garden shed wasn’t intended to live so long – in fact, I expected it to be scrapped well before I die as it’s in the way of my planned future reed bed system, and after the outhouse gets built that’ll be my next major expense work item. So I didn’t want to spend too much, and I guess one fifth the shed for half the price of the Asgard shed is the tradeoff you make.
All that said, Zhejiang Long Yard Industry & Trade make an above average product, relative to others I have experienced. Most of the steel sheet edges are folded back to prevent cutting your hands during handling, and I didn’t get cut once, so they did well there. The predrilled holes mostly lined up, which is better than average. In about four places the holes didn’t quite line up, causing some of the metal panels to bunch slightly which will let in a small amount of rain if there were a storm. There were only two places with completely missing predrilled holes, and those were easily drilled in by my own hand. They chose polycarbonate rather than cheaper and much inferior acrylic for the window. The instructions weren’t great – I’d look at them more as inspiration for writing your own instructions – but I’ve also seen far, far worse, and the numbers on the parts did match those in the instructions for the most part, except when they didn’t, none of which was a showstopper. One thing annoying about the instructions is the ordering of what to do in sequence, the design is actually better than the instructions give it credit e.g. they have a mini roof panel just big enough for your head to stick up through so you can easily screw in all the big roof panels without needing to hang over the roof from a ladder, yet the instructions completely ignored that quite nice design feature. There were sufficient quantities of screws, washers, bolts etc and then some, as it is good to have spares. As much as I’ve lambasted the thin steel sheet, it does have the one huge advantage of single handed ease of assembly because you can feasibly hold a whole sheet in an awkward position with one hand as you screw it in with the other hand. Good luck achieving that with 1.2 mm thick sheet, where assembly really does need two people start to finish.
I will admit it looks quite smart with its two tone paint job:
And, ultimately, once assembled it is sturdy enough and weatherproof enough to have solved what I bought it for. It’ll do. I can’t say I had any love for the quantity of time it consumed, the head scratching over what the instructions meant, or having at times to ignore the instructions because bits didn’t line up so I was going to have to think laterally. I’d have preferred an easier time of it, to be honest, given I had spent a grand overall on it. Still, it’s done now – well, actually, it isn’t quite done yet, I haven’t anchored it to the floor nor installed its floor concrete tiles, which you can see stacked there in front. Maybe by the end of this week!
House build spend
I undoubtedly overspent last year. In fact, due to bad record keeping by me we actually spent €10k over what we could afford, whoopsie. Which led to an unpleasant cash crunch after Christmas due to end of year taxes going out, and I didn’t quite have enough money.
Anyway, all that’s behind us now. My last update on this went up to 1st January 2023, and this will be up to 1st April 2023:
- Spent: €184,672
- Committed to be spent soon: €4,329
- Current three month averaged spend rate: €6,736 per month
The four biggest ticket items in the past three months were: (i) Lithium batteries (ii) 60.5 m2 of concrete ‘lego’ bricks (iii) Three phase solar hybrid inverter (iv) Concrete blocks and concrete tiles for shed.
I’ll almost certainly write a separate post about those concrete ‘lego’ blocks, which let you build a cheap earth retaining wall, so I’ll say no more about those for now.
Fairly obviously the big blow out spend these past three months were the inverter and batteries which I originally ordered last summer, and they finally turned up some eight months later. Those unlock me getting mains electricity activated on the site, which I have set in motion. That will cost me at least five grand, unfortunately the bank will require that a mains electricity connection be activated during the build, so you don’t get much choice (you may remember I did some calculations, and I reckoned it actually cheaper to buy and run a diesel generator even assuming they will need regular replacement than get a mains electricity connection installed and then pay its annual standing charge and running costs).
The second large upcoming cost will be purchasing those GARE pipes mentioned above, which needs to happen soon if I want them installed this summer as they have a three month lead time. Past those two big ticket items, I don’t expect any further large expenses in the next three months at the current time. If the AIB set achievable terms for any mortgage they offer, that might change quickly – I’ll need to bring on a structural engineer and a M&E engineer and each will cost at least 10k. And from June onwards, I would need to shell out a whole ton load of cash for any prepatory groundworks to install the GARE etc, which is a blocker for the builders commencing build. I suspect that would more than wipe me out for this year, I’ll need to wait to 2024 for more cash to continue the works.
I’ll start with the bad news: my mortgage broker who was handling the Permanent TSB and Bank of Ireland mortgage applications came back to me with unhelpful lending conditions. I had submitted the fixed price quote from EcoTech Homes which brings the house to Builder’s Finish for €606k, so to reach bare minimum viable for the purposes of ticking the mortgage lender’s definition of ‘completed’ at which point the mortgage turns into a normal not self build mortgage:
- Add structural engineering design: €10k.
- Add M&E engineering design: €10k.
- Add site preparation groundworks + ground-air heat exchanger: €40k.
- Add internal painting: €15k.
- Add kitchen, wardrobes, other joinery: €12k.
- Add bare minimum sanitaryware to reach mortgage completion tick box: €5k.
Total: €700k (rounded up)
Bank of Ireland and the Permanent TSB lend the following maximums for self build mortgages by first time homeowners, whichever is the lowest:
No more than four times your average income in the past three years (this is the Loan to Income limit set by the Irish government).
No more than the cost of construction (that would be the €700k above).
No more than 80% of the final valuation of the completed property.
It’s that last one which is my problem specifically, because there is absolutely no way that this property would be worth more than maybe €400k after completion, based on the historical property sale prices as recorded by the national property price register for that region. Therefore, the maximum that PTSB and BoI would lend me is €320k, leaving me €380k short.
At this point the two lenders varied slightly: PTSB wanted me to have the full €380k in cash in my bank account before they would lend a penny. BoI were marginally better: they merely want €350k in cash in my bank account before they would lend a penny. This cash sum must be unborrowed money AND I cannot take out any personal loans after they approve the mortgage, else the mortgage agreement becomes voided.
This creates a particularly large hurdle, because one needs working capital in situations where large outflows occur (stage payments to the builder) which are not replaced until large inflows to replace them happen (stage drawdowns from the mortgage provider, as self build mortgage pay in arrears so you need to front the cash for each stage).
I earn pretty well, but €350k in unborrowed cash is well beyond my means. It would take many more years of saving for me to reach that level of cash. Also, I could not spend any further cash on that site getting it progressed, because every euro I spend on it reduces the cash present hurdle those banks demand and thus puts me further away from acquiring a mortgage.
What is especially frustrating here is that those banks don’t disambiguate between a fixed price contract from a builder and going direct labour. The direct labour cost based on the other quotes I received I reckon is about €450k. The banks want to add +15% to that for cost overruns, so that’s €520k or thereabouts. Despite the obvious large gap in terms of risk and time over a fixed price quote from a professional builder, they treat those two quotes identically i.e. the cash hurdle that they demand before lending a penny drops by €86k, which is two years less time I would have to wait. But then I would have to manage the build myself, chase all the trades, and assume all the risk when a subcontractor does something which messes up the air tightness needed (or indeed anything else e.g. the foundations don’t match the superstructure, and they need to be with three millimeters of spec incidentally!).
This is bad news no doubt. There is one other self build mortgage lender in Ireland, which is the Allied Irish Bank. They’re still processing my mortgage application nearly two months after submission. They have the same lending conditions except that they will lend up to 90% of final valuation, so that’s an extra €40k. I am hoping given how long that they are taking and the extra paperwork they keep demanding that they will additionally offer a personal loan, which in Ireland is capped to €75k. That would supply €435k of lending, which would mean I need unborrowed cash in the bank of €265k before they would lend a penny. That is also well beyond my means, but it does lop a few years off how many more years I will have to wait.
In any case, the chances of commencing a build in 2023 now looks very unlikely . Key upcoming dates:
April 2024: Purchase contract requires build to be complete by this date, or the contract is breached. To be honest, even if the build started next month, given the delays in the building industry right now, completion by this date is unattainable.
December 2024: Commencement must begin before this date to get a refund of the 7.5% stamp duty paid for the transfer of land, which was €6,750. Also, the government subsidy scheme ‘Help to Buy’ worth €30k currently expires after this date.
The good news
Mains electricity installation is finally unblocked
Eight months after ordering the solar inverter and the lithium battery storage, those finally arrived while I was at Issaquah. I got the inverter mounted onto the wall ready for being wired in:
This is a 10kW Sungrow SH10RT three phase hybrid inverter. It isn’t the Fronius inverter I originally wanted, but those have lead times of three years right now, so if I wanted mains installed on the site any time soon then I had to choose a Chinese-made not European-made inverter. Sungrow historically are the most reliable of the Chinese inverters with a typical failure rate of 0.31% per annum for their last generation of inverters, this is actually slightly better than Fronius’ typical failure rate. They’re also a lot cheaper, and have some unique features e.g. a built-in mains isolator with < 30 ms switchover time i.e. they’re off grid capable by default, whereas the Fronius needs an expensive additional automated mains isolator added to it for similar functionality.
You do give up a bunch of stuff for the reduced cost however in terms of specification and flexibility. In particular, the Fronius can extract power much much better out of dull days where the solar panels aren’t getting much radiation. And the solar panel string configuration options are nothing like as flexible with the Sungrow, in fact, they are downright rigid, but as this will be a brand new install, we can design around that.
They also get quite hot during use, up to 70 C on the outside, unlike the Fronius which has active cooling. I have accounted for this with plenty of space around the Sungrow, including a metal roof which also doubles in keeping the sunshine off the inverter, as if it get too hot it cuts out.
One unique feature particularly useful to me right now is that the Sungrow is specifically designed to be detachable i.e. you can bring it out in the morning and plug it in, and remove it end of day into safe storage. As I don’t live there, this I will make use of on my site so it doesn’t get nicked.
Anyway, the reason I needed this before I could install mains electricity is because the ESB won’t give you a three phase mains connection unless you have onsite a three phase demand of sufficient power. They instead require you to install a small single phase at a hefty connection fee, then charge you a second hefty connection fee to upgrade the connection to three phase. As much as it cost me many months of waiting, buying these now saves me that second hefty connection fee. There is a further potential cost saving: most builders have to hire in generators which they of course bill straight onto you. If I have 20 kW of three phase mains power available onsite, that should eliminate the need to rent generators, and that will shave a further few grand off total build costs.
Other
I got the 2.5 mm2 three phase power cable and Cat 5 ethernet for the security camera trunked into the conduit for the far services box:
The blue back panel is a sheet of perspex I fitted into the metal back panel. This lets you drill in mounting screws without producing metal filings which are problematic for circuit boards i.e. the ESP32 microcontrollers which will eventually live in these service boxes.
I’m still working on the house (mid) services box, should have that done by end of this week.
I got the lighting inside the shipping container done, and an alarm fitted to the site office (note yellow siren up top):
Turns out that the double width LED strip consumes 113w, which you never know until you test it, as item descriptions for Aliexpress stuff tend to understate power consumption and overstate brightness. Excluding the power supply’s inefficiency, that is bang on 20w/metre, with the Aliexpress item listing claiming 16w/metre, so 20% understated which isn’t the worst I’ve seen. With the far end LED tube added that rises to 136w. The brightness in there is a bit overkill, the shipping container computer when I finish it will be able to PWM dim the LED strip down to perhaps as little as 40w and it’ll still be plenty bright enough.
The site office alarm is a Yale thing which works by AM radio waves. Aldi were selling them cheap for €70, about half their normal cost, so given how slow I am going on wiring up ESP32 boards to act as burglar alarms I figured this was worth the stopgap. It certainly works, the instructions it comes with are inaccurate so it kept going off during installation – indeed, the gards turned up at one point, which is nice to know that they actually do so when a house alarm goes off. With the help of the internet I figure it out, and it now is working as it should. It came with two PIR sensors and a door sensor, more than plenty for my little site office. Any attempt to knock anything off their mounts triggers the alarm, it also goes off if the radio signal gets interrupted. Not bad for €70. Only hassle going forth will be replacing batteries I think.
What comes next
By the end of this week I probably have to stop doing my own wiring, as a RECI certified electrician is needed to produce the ESB certificate of compliance necessary to get the ESB to install a mains connection. Wiring in 2.5, 4.0 and 6.0 mm2 leaf cable myself is one thing, wiring anything in which touches the ESB meter box (16 and 25 mm2 cable) is another. I have started chasing a RECI certified electrician, hopefully I’ll get him to turn up in the next few weeks.
Before any groundworks can occur, I need the ground-air heat exchanger pipes which are a special order with at least a six to eight week lead time, so if I want those installed this summer, I need to get a move on. I’ve started the process of ordering them and creating a storage holder for them in the shipping container as the bulk of those pipes won’t get put into the ground until after the house build is complete, so they’ll need to be stored for several years at my current rate of progress.
Other than that, everything else hangs around getting a mortgage decision, as until I know the exact hurdle they need me to reach, I can’t take any decisions. So here’s hoping that the AIB come back to me soon with a more helpful answer than the other two banks!
I’ve turned my attention since then to installing mains electricity into the shipping container, as I need much better lighting in there than my battery powered lantern. At the far end, I’ve raised the old florescent tube light which was in the kitchen of the house where I grew up – when they were renovating it, I claimed it from being thrown out, I’ve sat on it for years, and now it finally will go into use. That should put out about 5,000 lumen concentrated at the far end where it’s darkest. I’m also raising along one side of the container five meteres of double width LED strip angled 45 degrees downwards, and that should put out another 9,000 lumen. That should bathe in a fair bit of light eight metres of the twelve metre long container, and I reckon the door will illumate the first four metres just fine.
I made a bit of progress on the shipping container computer, but I got stuck for parts. I replaced the IRF520N solid state relays with IRF540N relays, as the latter ought to waste much less heat when derated to a 5v control signal. I found I had lost my 3.3v to 5v level shifters, so I had to order new ones. I soldered pins onto them today, so I just need to get everything wired up – well, and tested piece by piece carefully in case I accidentally shorted something.
Next weekend I head to Issaquah near Seattle for my first face to face WG21 committee meeting since the pandemic grounded all travel. I will be there for a week presenting four of my papers. I hope to get the mains lighting installed and fully functional in the shipping container before I leave, and I don’t have any ambitions this week beyond that.
One other big advancement which I think I got done is to get a mortgage application submitted. It took many more months than I could have ever expected to submit a mortgage application. Firstly we were blocked on my accountant to produce company accounts, which they didn’t complete until December. Then oodles of documentation had to be collated, because the bank/broker seems to think more information is always better, even though they clearly get overwhelmed by the complexity of it all. Then everybody seems to take at least a week and a poke from me to respond to say they need even more documentation. Nobody has actually confirmed that any application has been submitted yet, so I don’t actually know if it’s in. But that alone has sucked down a month, and the banks likely will take another six weeks to decide anything. So it’ll likely be mid April before I know whether a build commencement in 2023 is possible, or whether we’ll have to wait until 2024.
I’ve been disappointed at the lack of quotes from builders, out of thirty requests for quote dispatched, I got just one to take it to Builder’s Finish; one to take it to Second Fix; two for the superstructure only. That’s it. Some builders were blunt enough to say their order queue is full, and a passive certified build is added hassle for them which they don’t need to bother with by sticking with NZEB builds only. Last year Ireland broke its annual record for new build commencements, so no doubt that pipeline is full. However planning permission applications fell off a cliff last year, so I’m guessing that pipeline should start emptying out by 2024.
So maybe if the build commencement does get pushed into 2024, it’s no bad thing overall in terms of cost and build times. Still rather frustrating however, one is within spitting distance now. Just not there yet.
Satellite imaging
Oh, I did do one other thing: I bought an up to date satellite image of the surroundings of my site. This might sound like not a big thing, after all hasn’t Google Maps been shipping high resolution ‘satellite’ images for years now? However, firstly, Google Maps uses really old images, its one for my site are at least twelve years old, and probably fifteen. Secondly, Google’s ‘satellite’ images actually come from an airplane because the 5 - 10 cm per pixel resolution images Google has are definitely top secret nation state spy satellite type of resolution, and an airplane is way cheaper than one of those, even if Google were allowed access to one.
In fact, buying aerial images is straightforward in Ireland. If you go to https://store.osi.ie/aerial-imagery-map.html, for €31 you can get a 30 cm per pixel resolution image for my site. Unfortunately, the most recent images available are from 2014.
Up to date satellite images are until just very recently not for the retail customer to purchase. The reason is cost, you can purchase them yes, but they require you to buy the whole sweep, and it’s at least several tens of thousand of dollars. On HackerNews I noticed that a startup called SkyFi finally had the bright idea of parcelling out those images in much smaller chunks for much smaller prices, ones affordable to the likes of me.
SkyFi’s pricing for my location was US$4 per square kilometre, with a minimum order of five square kilometres, so US$20 before VAT. For that, they would provide an image which captures detail over 75 cm taken in the past year. They don’t have any higher resolution images for my location unfortunately, though they do have a multispectral image a few years old with less resolution, and much higher minimum order area.
Here is SkyFi’s 75cm resolution image from 26th March 2022 11:16am cropped to match the size, but definitely not the resolution, of Google’s Maps:
Undoubtedly the SkyFi image is a pale comparison to the Google Maps image. There are some sensor blowout issues from brightness, and the lack of detail is quite disappointing.
I reckon there is approximately between a ten and a sixteen fold difference in resolution, though note that your web browser may actually be showing you a reduced resolution edition of the Google Maps image, as it is quite high resolution. At 75 cm per pixel, my site there is a mere 53 pixels wide and 52 deep, the house might be 25 pixels wide by 10 high. This is probably such low resolution as to not be particularly useful, true, but much more important here is that I can get a recent satellite image of my site for a small fee. That is very new, and very exciting, because it really won’t take long at all for pixels per dollar to dramatically improve. Commerical imagery already comes in 15 cm per pixel which is 5x better, albeit SkyFi doesn’t offer that yet, their current best is the next grade up after 75cm which is 50cm which I doubt is worth the money for my use case, as it’s only one third better. SkyFi say they’ll be selling 10 cm per pixel images by 2024 however, and that’s not far off Google Maps’ quality.
Out of interest, I looked into how much it would cost to get a man with a drone out to take aerial shots. €550 apparently. For not much more, I could buy a mid range drone with 48 megapixel camera and capture my own aerial shots in glorious 5 cm per pixel resolution.
Apart from the thrill of seeing from the sky the fruits of your labours, I suspect aerial images aren’t actually that useful for a site as small as mine. Well, at least compared to a professional survey anyway. I have a measuring tape long enough to traverse the entire site, so if I need to figure out if something is or isn’t where it is supposed to be, I can just roll out my tape and have a quicker and cheaper answer than any other solution. In that sense, these satellite images are pure navel gazing.
Am I going to spend another €25 inc VAT to get the latest satellite image when SkyFi updates it in April? To see the roof I erected, my shipping container, my portable cabin, and my other works? The chances are high. I like navel gazing!
You can see the four conduits coming out of the ground, with 16 mm2 cable sticking out the top. I’ve since fitted conduit to connect those up and back to the central services enclosure, though I haven’t got to fitting the 25 mm2 earth cable connecting those 16 mm2 earth rods yet. Each earth rod is four foot something long, and is at least a half a metre under the ground, so in theory especially given the high water table there should be a good earth connection here.
Given I was hand shovelling soil, I took the opportunity to do a soil test:
I make that:
- Total height of settled material: 56 mm, maybe minus 2mm for glass = 54 mm
- Height of clay layer: 2 mm (3.7%)
- Height of fine silt layer: 23 mm (42.6%)
- Height of course silt layer: 29 mm (53.7%)
Which is a silt loam soil, which ought to be very fertile and excellent for the vegetables I intend to grow. Drainage will be an issue however, during all that rain during November it was extremely clear that the site struggles to clear all that rainwater on its own – indeed, the house being built next door the entire of their back garden flooded, and had at least four inches of water for the entire month. The only reason it didn’t flood into their house was because their back garden was overflowing onto my site, which won’t be possible after the wall goes in. I don’t know what they’re going to do about that, but I suspect that the builder will consider it not their problem and the new occupants will get an unpleasant and expensive shock after they move in. If I manage to catch them visiting I’ll mention it to them.
I suppose the only other thing where I’ve made visible progress is wiring up the intelligent solar charge controller:
Top right is the ESP32 board with PoE ethernet, though in fact it’ll be powered from the USB socket on the dumb charge controller. Underneath it is a 3Ah LiPo battery, so the ESP32 still has power when everything is turned off. Just above it is a small low power 120 x 80 OLED screen. There are four MOSFETs for PWM dimming a five metre dual column RGBWW LED strip for lighting the inside of the container; there is a relay to disconnect the dumb charge controller from the battery; there is a voltage and current sensor so we can measure how much is left in the 12v battery; and finally there is a coin battery powered real time clock, as the one in the ESP32 is well known to be garbage. I’m still missing a few bits – there is a 12v to 24v boost converter, as the LED strip runs off 24v; a tilt sensor still needs to go on to detect if the container is being lifted by a crane; I still await from China a 3.3v to 5v boost converter, as the relay needs 5v, and we need to be able to turn it on using the LiPo battery when everything else is off. The LED strip is able to draw 90 watts at max power, so max current draw should be under 8.5 amps, hence I fitted a 10 amp fuse.
The 12v battery was reclaimed from an old UPS, I reckon it might have 50-60 watt hours capacity in it, which means I can’t have that LED strip on at full brightness for more than thirty minutes. This kinda sucks, however I hope it won’t be too long before I get mains power, and then the 60v DC mains circuit can power the LED strip and not require anything from the battery. The battery then can serve its primary purpose as a theft alarm even if somebody cuts all the wires into the container before stealing it.
House build spend
As I mentioned last post, I am now out of money so my cash burn rate has significantly dropped, though I did take advantage of the November sales (Single’s Day on Aliexpress and Black Friday over here) to pick up some longer term items needed at discounted prices. My last update on this went up to 1st October 2022, and this will be up to 1st January 2023:
- Spent: €164,463
- Committed to be spent soon: €14,341
- Current three month averaged spend rate: €1,377 per month
The four biggest ticket items in the past three months were: (i) Quantity survey (ii) Three tonne digger hire (iii) Wifi and fibre optic router boards for house (iv) Conduit, concrete screws, conduit mountings.
We’re heading off to the US tomorrow to see Megan’s family, so no more work shall occur until we get back. Have a Merry Christmas everyone!
I did get this finished in the past month however:
Strictly speaking, it’s actually the last four months because I bought the roof sheets in July, and it’s taken me well over two months to get the wall painted and to erect the support beams. As much as that was painstakingly slow, the beams have been designed to aid installing wiring and lighting, so they will enable subsequent stuff to go quicker. And, I now have a sheltered place for the solar inverter and all the other wiring to be installed (plus, that roof is absolutely super when a rain shower comes in, you can go hide under it until the rain passes, or get a lot of cutting and sawing type of work done when it’s raining full belt). The roof panels cost a few hundred euro, as did the paint, as did the raising of the wall. I reckon €1,500 or so of materials has gone into just that little bit of wall. Crazy for what it got me, but that’s the cost of construction I guess. And still vastly cheaper than getting somebody in to do the same work.
I’ve got plenty to keep me busy left to go – conduit needs to be installed for ethernet, 16A three phase mains, local earth and 60v DC to run to the far end of the existing wall. RGBWW outdoor strip lighting needs to be installed under the roof, after waterproof flashing between the roof and the wall is installed (I await a few dry days in vain I suspect). I have two watertight large plastic boxes for wifi APs for each end of the wall, and two security cameras to raise each end of the wall. I have a 12v battery powered alarm system to install, with a roof mounted trickle charging solar panel, and some 50 watts of alarm siren to light the place up if somebody tries to burgle it. At some point the solar inverter will turn up, that and the lithium batteries will need installing. I have months of work ahead of me before I can move in as my daytime work office.
I’m currently working on that 12v system for the container. It will consist of one of my Olimex ESP32-POE boards, a 5m RGBWW PWM controlled strip to light the inside of the container, an infrared movement detector, oodles of 12v siren capacity, a 20w solar panel, a solar charge controller, and an old 12v battery reclaimed from an old UPS which after me reconditioning it appears to still be able to hold 50-60 watt hours. The total cost for all these parts was under €100, which puts the expense of that wall into perspective. Still, I need to wire this up and get a firmware onto it.
The solar charge controller is really cheap and dumb. It draws off the 12v supply to run itself obviously, but it doesn’t turn itself off at nighttime, so it therefore drains the battery for zero good reason. I am therefore going to insert a mechanical relay between it and the battery, and have the ESP32 physically disconnect it each night and reconnect it in the morning. To achieve this, the ESP32 obviously enough needs to know when the sun will rise and when it will fall. Complicating this is that one of the many quirks of the ESP32 is its shitty real time clock, it will happily wander by minutes per day if the CPU is running, but worse, if you put it into deep sleep then it wanders by hours, and obviously I intend to deep sleep it when it’s not needed. To solve the real time clock problem, I bought a cheap DS3231 i2c connected battery powered real time clock which won’t drift more than a minute per year, so now the ESP32 always knows the correct time and date. The next problem is calculating when the sun rises and sets for a given latitude and longitude and date.
The correct solution can be found at https://gml.noaa.gov/grad/solcalc/solareqns.PDF, and it involves lots of maths because the earth isn’t quite a sphere, and it doesn’t go around the sun linearly – it actually slows down and then catches up across the year as the other planets (mainly Jupiter) tug on it. The ESP32 only has hardware floating point for adds and multiplies, everything else is hideously slow, so whilst that is a once per day calculation, I was hoping to derive a simplified estimator of sunrise and sunset for a latitude by assuming that the earth is a sphere and its motion around the sun is linear. I think I have derived a correct simplification:
# Turn your latitude in degrees into radians
latitude = (52.129877 / 180) * math.pi
const1 = 12 / math.pi
const2 = -math.tan(latitude)
const3 = 0.40910517666747085283091311613373
const4 = 2 * math.pi / 365
def calc_sunrise_sunset(days):
diff = const1 * math.acos(const2 * math.tan(const3 * math.sin(const4 * (days + 284))))
sunrise = 12 - diff
sunset = 12 + diff
return (sunrise, sunset)
# Normally pass this time.gmtime().tm_yday
sunrise, sunset = calc_sunrise_sunset(81)
# Must be true at the equinox
assert abs(6 - sunrise) < 0.01
assert abs(18 - sunset) < 0.01
This costs a sine, a tangent and an arc cosine plus three additions and four multiplies. The trig functions will be implemented on the ESP32 as a sequence of Chebyshev multiplies and adds (maybe six of each per trig function?) giving maybe 20-25 adds and 20-25 multiplies, so I’d consider the above fairly optimal. It’s not the most accurate estimator as it is too simplified, it can be up to 45 mins out depending on the time of year, but for my needs I think it’ll do just fine.
Despite what I said earlier about not having any more money to spend, I did take advantage of the Chinese Singles Day sales to pick up an Anycubic Kobra Go 3D printer this past month for under €200 inc VAT delivered. This is a self assembled printer capable of printing in PLA, PETG, TPU, ABS and low temperature formulations of Nylon (just about!) to dimensions no larger than 20 x 20 x 24 cm. It’s very much conventional bog standard cheap 3D printer tech, albeit a very well put together package thereof, so you get what you get for the price point i.e. it’s going to be very slow if you want quality, but all the parts and firmware are the same as any other printer in this price bracket, so it’ll be very easy to maintain and/or upgrade.
My experiences with the printer so far have been extremely positive, given its price. It is perfectly calibrated i.e. 1cm in X, Y or Z on the computer is exactly 1cm in the print. I have been feeding it extremely cheap filament – as in, rock bottom cheap – and the results have been very good considering that. Here is the owl print Anycubic supply with all their printers for you to test its assembly:
This is the owl straight out of the machine uncleaned, and the small amount of ringing at the bottom came off very quickly with a knife. Look at the ears – that is a mightly overhang, yet they do not sag despite the printer going at maximum speed with a 0.2 mm layer thickness.
I’ve had the printer for a few weeks now, and this weekend after much earlier testing to ensure this final test wouldn’t be a waste of a lot of filament, I set it printing this over thirty hours:
(Note the roughness of the bottom half, and the smoothness of the top – a classic example of the effects of moisture getting into the filament. It doesn’t matter for our use case, we’ll be enrobing this with several layers of epoxy resin, which will produce a glossy ceramic-like finish)
That’s the full height (24 cm) and most of the full width and depth (20 cm) using a single thickness over-extruded wall i.e. if anything, absolutely anything, were out of balance or wrong this print would have failed. The nozzle is 0.4 mm wide, but I had it print this by depositing 0.6 mm of material (over extrusion). Obviously, this is highly prone to slipping unless the material is placed absolutely perfectly on top of the preceding material down to micrometre accuracy, and as you can see, the printer is capable of that, albeit it had to run at half speed. There was almost no fluff – only a marginal amount along the Y axis due to the bed slinger – no ringing, no holes, no deformations nor errors of any kind. If you’re willing to wait, this printer is supremely capable at half speed, the quality is second to none. What a more expensive model will buy you is speed, the 3D printing world is currently abuzz about the Ankermake M5 which costs 5x-6x more than mine, but also prints maybe 8x faster using proprietary nozzles and other fancy technology. Indeed, after a few years of stagnation, it looks like a real technological leap forwards is currently happening in consumer 3D printing – high end features typical in industrial printers are increasingly appearing in sub-€1000 consumer printers, and it’s not hard to imagine that in a decade from now for under €500 you’ll be able to buy a 3D printer capable of all non-organic materials printable under 350 C which can ‘plug and play’ turn out a fifty litre print within 24 hours with almost zero chance of print failure.
Speaking of print failure, I ended up spending as much as I did on the printer on preventing print failures. I bought a large sized filament dryer, an enclosure and vacumn seal bags with dessicant for the filament reels to try and keep the moisture out of them. Where I live in the south of Ireland typically has relative humidity exceeding 80%, and I’ll be keeping the printer outside in the garage where it is particularly moist (right now, condensation drips constantly from the roof!) as you can’t safely print ABS indoors due to the fumes produced. I’m hoping that between the filament dryer and the enclosure I can get away with printing in the garage, I certainly don’t have the space here inside the rented house.
I mentioned earlier that I very much cheaped out on the filament. Most filament if bought in Europe costs €20-30 per kg, and if bought from China once you add in the postage it is usually around the same for non-commercial quantities. Bulk filament manufacturers such as https://gst3d.eu/ will get you down to €15/kg if you buy > 10 kg at a time, but if you really want to get down to cheap cheap cheap filament then YOYI filament from Amazon kinda occupies the whole market below €15/kg in Europe at least. I picked up my YOYI filament for €10.50/kg delivered, to reach that price I had to buy 4 kg but I was allowed to choose any colours or materials (PLA, PETG, TPU, ABS) I liked. Remarkably, YOYI charge the same for PLA, PETG and ABS, only the TPU is more expensive.
Based on internet reviews, YOYI filament can deliver excellent results but it is finickety and intolerant. I’ve only had a bit of experience with it, however I can confirm other reviews that for the grey PETG, you need >= 230 C nozzle with a >= 80 C bed for the first layer if you want bed adhesion after which you can dial back to 210-220 C nozzle to reduce stringing. It’s kinda annoying having to hang over the printer until the first layer is done, so when Raspberry Pis return into stock I hope to kit out the printer with a Wifi Raspberry Pi based print manager and then I can watch and control it via Wifi connected camera from within the warmth of my home. Still, for a one third reduction in the cost of running – given the amount I expect to print – I’ll take it.
This brings me to why I bought the 3D printer at all – I have found myself increasingly needing custom plastic parts, and having to work around the lack of them is costing me time and money. I intend to teach myself over the next few weeks how to design end to end a 3D print – so far, I have taken other people’s designs from the internet, sliced them for my printer using my own hand and judgement, and so far so good it appears I understand the tradeoffs given that all my prints to date have been successful. But where I need to get myself is the capability to design and print say a durable custom waterproof case for an assembly of ESP32 automation board with various modules and sensors, which is almost certainly going to require PETG or ABS. PETG is the same stuff from which they make disposable drink bottles, so it’s quite durable and capable. However, ABS has the unique ability to be postprocessed using acetone i.e. if you ‘paint’ an ABS print with acetone it ‘melts’ the plastic, which means you can seal the print against everything other than organic solvants, which includes the rain. Unfortunately, printing ABS is both tricky and toxic, so I’m semi looking forward to attempting a print using the cheap cheap cheap YOYI ABS filament spool I bought, maybe next weekend or the weekend after.
Here’s an example of the kind of custom plastic part I need, these were printed a few hours ago in that YOYI grey PETG using a 0.1 mm layer rather than 0.2 mm to improve vertical strength and resolution:
Despite the low post-first-layer print temperature there was a bit of stringing, but it was very easily cut off to yield the above. These brackets aren’t pretty, but they are functional – they clamp any 65 mm wide circuit board, which is most of the Olimex stuff. That means I can finally mount the Olimex stuff onto an acrylic board, and that in turn means no more rat’s nest jumble of wires and modules with so much that can short or get loose or get tangled. Everything going forth will be fixed onto a solid board and immovable, woo hoo! Down the line, as mentioned earlier, I hope to print waterproof custom cases, but for now even these simple printed mounting brackets will be a big time and hassle saver.