Niall’s virtual diary archives – Sunday 13th November 2016

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Sunday 13th November 2016: 2.46am. Link shared: https://passivehouseplus.ie/magazine/new-build/west-cork-passive-house-raises-design-bar

Went to visit the unusual passive house below today (lengthy article about it linked) which was a four hour round trip drive. An engineering triumph no doubt, floor to ceiling sliding windows almost entirely throughout and a non-cube and therefore hard to prevent air leaks layout, yet requires I think the architect said measured at just 8kWh/m2/year which is far below the upcoming EU Near Zero Energy Buildings (NZEB) mandatory maximum of 45kWh/m2/year from 2021 onwards. The view was really amazing with all that glass and such an amazing location, but I find much worry with the surely enormous cost of the build. My budget would max out at €250k assuming the banks are kind to me, and forget about anything like a house like the below for such small change.

I also, personally speaking, found the air a bit stuffy with so many people in the house. Passive houses are nearly airtight so too many people breathing can be hard to dissipate so much CO2, plus Megan noticed how hot it becomes so quickly in a single room when the sun lands where it rapidly become unbearable. You are supposed to manually crack open two windows to create a cooling through draft and indeed they have insect preventing meshes built into the windows exactly for that, but I have to say I found that whole manual approach to emergency ventilating a room a bit underwhelming if understandable if you're trying to minimise energy consumption and get the occupants proactively involved in that.

Personally speaking I'd use the passive house energy savings to treble or quadruple the ventilation flow. Lots of ducting pumping air in from the ground and out from the ceiling as a sort of American style central air, albeit with much larger ducts and far slower fans so it's unnoticeable. Ideally it could adjust itself automatically to individual room load so if fifty people all bundle into a single room, the ducts in that room go full belt. No idea if this is possible, but that's what I'd want personally - similarly to those energy saving lightbulbs, rather than sit in poor quality light saving energy I'd use the energy saving to increase the illumination significantly for the same cost as incandescents. What I want is the same for my house, and that it auto adapts to balance the whole house without me doing anything. And for a realistic budget.

Don't get me wrong, the 2021 NZEB efficiency limit would still be met. Much the same as the difference between LED bulbs and CFL bulbs, LED are considerably more efficient than CFLs but the cost benefit is far lower because in absolute terms 40% of pennies is still pennies. Similarly, a certified passive house might be several times more efficient than a 2021 NZEB house but if you're spending less than a grand a year for your entire NZEB home then dropping that to a few hundred euro per year isn't actually that much in the bigger picture. Better instead in my mind to spend that few hundred euro on a far improved fresh air supply. It's worth it.

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