Air test
Entry posted by jamieled
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Only a short update for now and a distinct lack of photos. I'll put something more interesting up in the next week or so. Suffice to say that combining work with trying to get to completion has been quite difficult. Throw into the mix that my other half is shortly due to have twins and you understand why I'm often getting comments like 'do you ever think you've maybe bitten off a bit more than you can chew?'.
One milestone recently was getting our air test done. I've decided to write a bit about this as a) There seems to be a fair bit of interest in this on buildhub and b) our result is not quite as I'd hoped and so I thought a few musings on this might help others.
I haven't had the actual test report through, but from the results I saw on the screen, we ended up with a value (no laughing please from the passivhaus crowd) of around 3.4 m3/m2/hr. This is fair bit higher than I'd hoped for, but as I'll explain below, maybe not too surprising.
The guys who ran the test spent a bit of time wandering round trying to find leaks and allowed me to do the same. There were no areas of the house where they could find significant leakage, but one or two small leaks easily dealt with. This obviously leads to the question of where it's all going. For reminders, our house is built from 300mm I-beams, filled with cellulose and then boarded with OSB on the inside, with all joints taped. All the services are ducted in and the ducts sealed. Windows have expanding foam strips around them and are taped. I don't think I'll ever know where the weaknesses are, but my suspicion is now around either 1) the OSB itself and 2) Where the 1st floor joists meet the outer rim board (a detail I failed to think through before it was too late).
If I look back on some of the build, I think that I probably didn't spend enough time figuring out some of the detail earlier on. That said, I had a distinct lack of housebuilding experience when we started, and so I spent a lot of time trying to figure out the basics of drainage, roofing, cladding etc etc... It's now quite clear to me that if I was to have done better on some of these small airtightness details, then I'd have had to either take a lot longer on the build or go down another route (perhaps buying a kit with a minimum guaranteed airtightness?).
Anyway, disappointing thought it is, we're in November, it's about 2 degrees outside and the house is toasty and will keep its heat well into tomorrow. While there would have undoubtedly been some benefit in getting it more airtight, it's a lot better than anywhere else we've lived. Frankly, my disappointment was pretty short-lived as we have more important things to worry about. Final bits before I can apply for completion are the access ramp and some outside drainage. Oh, and then the twins might arrive...
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