The role of air tightness testing in energy efficiency
Imagine that the Okanagan is having one of it’s really cold days. You pick out a warm coat, hat and gloves, put them on and walk outside — without zipping up your coat. While parts of you are fully covered, cold air is going to continually sneak into the opening of your jacket. No matter how insulating the jacket is, if cold air gets through you are not going to be comfortable.
No matter how warm your jacket, if you don’t zip it up the cold air is going to get in
The same thing goes for your house. The walls of your house are meant to keep the weather outside in two ways: first with good insulation and then by sealing out air leaks. ASHRE standards say that homes should have a minimum of 0.35 air changes per hour (ACH). You can think of this as replacing 35% of the home’s air every hour or think of it as taking nearly three hours to completely refresh the air. Often people counter that a leaky house is “healthy” due to lots of fresh air. A typical house exchanges its air every 15 minutes, much more often than what is required for fresh air. You will actually be able to detect this current as cold drafts and you will certainly notice it when you pay your heating bills. Well insulated houses exchange a steady stream of air with the outside, while leaky houses can have rapid air exchange when it is cold and windy and less air exchanged when it is warm and calm.
Since reheating the house every fifteen minutes is a waste of energy, the BC Energy Step Code has included air tightness testing into the very first step of the code. If you are building a new house where the BC Step Code has been adopted (Kelowna, Penticton and Lake Country, soon Revelstoke, West Kelowna, Vernon, Peachland, Summerland and Salmon Arm) your builder will meet with an energy advisor. The advisor will use a large fan to pressurize the house and will measure the number of air changes per hour and locate where the house is leaking. The builder then has the opportunity to fix the leaks inexpensively before the house is completed.
If you live in an older house, is it worth having an energy advisor test your house? Absolutely. They can identify the source of the leaks, some of which can be easily fixed. You can do it yourself or hire a contractor. However, the current BC Step Code only applies to new houses and buildings. There are plans in the future to write a specific step code for renovations.
Canada as a whole is due for a building code update. The National Building Code (NBC, small buildings like houses) and the National Energy Code for Buildings (NECB, for larger buildings) are in the process of being updated to a step code. Unfortunately, the public comment period happened in May, while many of us were glued to COVID news. During that time the code was revised to remove the requirement of airtightness testing. This is unfortunate — not only does air tightness testing bring the energy advisor into the process early enough to improve the building, but you cannot get maximum efficiency out of a building that is actually leaking air.
You cannot get maximum efficiency out of a building that is actually leaking air.
Gerry Sawkins of 3West Building Energy Consultants says “At this time the NBC 2020 is not released and is slated for late 2021. Until it happens, all bets are off but it is a mistake if they eliminate it [air tightness testing] completely…in the long term BC currently requires testing and for NBC to not require testing is a big mistake.”
READ MORE: A new way to build
That brings us back to the coat analogy — it is not enough to have a warm winter coat. You actually have to zip it up.
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Kristy Dyer has a background in art and physics and consulted for Silicon Valley clean energy firms before moving (happily!) to sunny Penticton. Comments to Kristy.Dyer+BP@gmail.com
Kristy’s articles are archived at teaspoonenergy.blogspot.com