Malcolm Isaacs from Construction Maison Passive (and CanPHI) came over today. We hadn’t seen Malcolm for quite a while; he’d been much more involved in the earlier stages and was responsible for supplying the CLT, wood fibre insulation and the Optiwin windows and doors that are the basis of the house construction. Malcolm was here to do several things…
The first was to conduct some repairs on the Motura sliding door on the south side of the house. This door, which was a new model from Optiwin and untested in practice until we installed one, had seemed not be as airtight as it should have been. Some of the gasketing on the bottom corner has also been damaged, although it’s unclear whether this was related to the same teething problems or whether it was to do with the conditions on the site. The company investigated and supplied us with some new gaskets and other components, which Malcolm brought with him to install. This involved the crew taking the very heavy sliding element out, adding gaskets, and replacing it several times until everything was right. One of the new gaskets will also require some specialist fixative for which we will have to wait until next week so it remains unfixed. Otherwise – it’s all sorted out.
The second thing was to do a blower door test. Blower door tests are absolutely vital in establishing the air-tightness and therefore, along with the insulation value of the building shell assembly, the energy-efficiency of the house. Old houses without a ventilation system actually require the shell to be less tight because otherwise there would not be sufficient air replacement for people to live and breathe comfortably, but a passive house with mechanical ventilation should be as tight as possible.
There are many sites that can help you understand how tightness is measured. Green Building Advisor has a good historically informed North American account here, and the Passivhaus Institut’s Passipedia provides the (European) Passive House perspective here. Basically, you seal up the house with specially designed materials and blow in air with a fan to pressurize the interior of the house until the difference between the exterior and interior is 50 Pascals. The fan is attached to a measuring device from which, you can then measure how much air is needed to be added to the house to maintain that 50 Pascals difference (in other words, how much air is leaking out), a value known as cfm50. If you know the overall volume of the house, you can then calculate a second, more important, value: Air Changes per Hour, ach50.
It’s amazing how standards have changed, and expectations still differ across the building industry in different countries. Green Building Advisor says that for normal building in North America, an ach50 of 20 is leaky, and 5 or 6 is tight. The toughest Canadian standard, R-2000, which is much tighter than anything that normally gets built here is 1.2, but the Passivhaus Institut insists on 0.6!
Enough background. How did we do? Well, even with the remaining unfixed gasketing on the Motura door, the house still achieved an ach50 of 0.44. We think we will probably get that down a little bit more when we finish the door sealing, but there is no point in doing anything more than that. It is well within Passivhaus levels and almost three times as tight as the R-2000 standard.
Finally, the third job today was to balance the Zehnder ComfoAir 200 Heat-Recovery Ventilation (HRV) system. Brent Carkner from TBC Mechanical Design had finished off the installation of the system earlier in the week, but few people, even in the industry, have the sophisticated active flow device needed to get the balance right. Malcolm has one of these and got to work on making sure that the same amount of air was being drawn in as was being sent out by the system. It’s now working pretty well, however he ran into some issues around how to adjust the power levels on this system, so he’ll have to talk to Zehnder and come back some time soon. Thanks, Malcolm!