Sept 2024 - 2 - Airtightness Testing - Builders Fan
A site where the airtightness target has not been met.
Builder unhappy, architect unhappy, everyone unhappy.
Luckily, the builder had the sense to do this test at a relatively early stage in the build, so the airtightness layer is still visible.
However, an airtightness tester can only stay around a site for so long, and at the end of the test window there were still many leaks being found.
So, it was recommended to the builder to get a fan and depressurise. As long as there are leaks that can be felt by hand, there are leaks worth fixing. The only trouble was how to calibrate the fan so that it doesn't pull too much.
Well, ideally, the fan used would have multiple speeds, and go slow at first so as to not build too much pressure and perhaps cause something to fail in the airtightness layer - a membrane pulling off the wall or ceiling, for example. In the end, we checked the pressure generated by this 2 speed fan on on its lower setting - 72Pa! So a bit high to be running for a prolonged period. Rather than block off the fan a bit, as happens with the airtightbness testing fans, the builder has opted to open a door or window a crack and allow some pressure to be relieved, and to continue looking for leaks.
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There have been specific fans developed for example this purpose - the Wincon from Proclima and the Irish made Zephair are examples, but these are hard to get your hands on these days.
Sept 2024 - 1 - HRV Filters
You hear about the importance of cleaning and/or replacing filters in the HRV systems, but it is seldom we in Greenbuild get to see them much after installation, as most of the houses we test with HRV are new houses, and older houses we test tend to have DCV or natural ventilation and so not have filters.
Recently, we tested a house completed near the end of 2023, where the owner was in a rush to occupy and simply hadn't gotten the testing done yet.
When I asked about the filters in the HRV, he said they hadn't been touched since installation. So we had a look and found this:
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Not a pretty sight!
Jan 2024 - 2023 in Airtightness, brief overview
Just for interest: the best and worst tests of the year in 2023
| Best Air Permeability test | Worst Air Permeability tested New build |
Worst Air Permeability tested Existing |
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| 1 | 0.193 - timber frame single home | 10.33 - new, fancy, home.
Finished and occupied. Would normally have been expected to be less than 5 m3/hr.m2. |
22.12 - Old Georgian Red Brick house, long time converted in offices and about to undergo more work. Just the older part of the building - not including the newer rear section |
| 2 | 0.384 - timber frame single home | 9.95 - School extension | 17.13 - 3rd Level instituation building, probably from the 1980's. |
| 3 | 0.437 - timber frame single home | 8.69 - terraced new house.
Many on this estate failing at the first test (i.e. worse than 5 m3/hr.m2); possibly because of jutting out stonework or single storey juts or overhangs. But this was the worst. |
14.86 - single home, cold in home survey |
The three best results are all from the same timber frame supplier this year, as they were in 2022. The best we tested that was not from them was q50 of 0.636 m3/hr.m2 on an apartment in a block, where a number of the apratments would be testing at 1 m3/hr.m2 or less; and an owner-builder self build at 0.704, which also met the Passive House standard for airchanges at 0.567 ACH @50Pa.
By the way, where the test is over the allowed limit, there is typically a retest on another day, following rectification works. We do not report on that here.
