by Lloyd Alter –
CC BY 2.0 Lloyd Alter/ pre-renovation blower door test
When you go to the doctor, you don’t tell him what your blood pressure or pulse is, he tests it. But when you go to your contractor and ask if your new house met code requirements for air tightness, most of the time they will just say sure. But the 2015 International Energy Conservation Code (which is American, not even recognized nationally, let alone international) requires that the house gets tested for the building equivalent of blood pressure, which is air tightness. Few states have picked up on this, and as of October 3, New York State has made blower tests mandatory.
The standard adopted in New York is for 3 air changes per hour at 50 pascals of air pressure difference, which is not particularly hard to achieve. But according to 475 High Performance Building Supply,
…even at “just” 3.0ACH50, increasing the airtightness of the building envelope will make a huge difference for the comfort and the energy efficiency of projects built to current code. These minimum code requirements are there to not only warrant the safety of the construction, but also to lower energy usage that will help achieve climate protection goals – while making buildings more comfortable and resilient.
It certainly is not as low as the Passivhaus people would want (they go for only 0.6 air changes) but building science expert Joseph Lstiburek makes a persuasive case that it is a reasonable and achievable number. (See his hilarious take on it here). Joe calls blower door tests “a quality control thing.” Which is exactly what we need.
Lloyd Alter/CC BY 2.0
Blower door tests cost a couple of hundred bucks and take a few hours of preparation, so it is no wonder that builders complain and that they are not required everywhere. Getting to 3.0ACH50 requires some care; 475 notes (and lists some of their products in this):
We know that building to 3.0ACH50 is possible for contractors that pay sufficient attention to details, such as using gaskets around pipes and cables, taping sheathing, using good quality weather resistive barriers with taped overlaps, connecting all window openings with the right tape, and using INTELLO Plus as an interior air barrier. Last but not least, the floors and ceilings must be continuously connected to the air barrier. If these steps are taken, houses should easily pass this code requirement.
It’s not so hard to hit the standard and it is not so onerous to ensure that the work is done right; as Ronald Reagan used to say: “Trust, but verify.” Good advice. Every state and province should require this and if they don’t, the home buyers should.
UPDATE: Here is a great explanation from the Urban Green Council.