Air infiltration, building airtightness, indoor air quality and air sealing provide unique challenges for us at Advantage Home Performance. We recognize that if a house has excessive air leakage the house will be uncomfortable and expensive to heat and cool. The other extreme is a house that is too tight and does not have any provision for fresh air ventilation will be more susceptible to indoor air quality problems. This article focusses on homes that are too leaky. For a more in-depth discussion about building airtightness, combustion safety and controlled ventilation, see our article on “Indoor Air Quality”. Our goal, given our customers budget and the realities of a building, is to find the level of building airtightness in which we get the optimal level of comfort, efficiency and indoor air quality.
Measuring building airtightness
A blower door is used to measure a home’s level of airtightness. We can determine fairly quickly if a house is leaky, tight or about right given the size of the house and the number of occupants living in it. The blower door also permits us to calculate the approximate size of the hole that would be created if all the unintentional holes were combined. We use this information to help us determine what solutions would make the house more comfortable, energy efficient, healthy and safe.
Another benefit of using a blower door is that it can lead us to the unintentional holes or air leakage sites. Most homeowners are under the false impression that air leaks around windows and doors. Most homes are full of hidden holes that let conditioned air escape. These same leaks can negatively impact the performance of the insulation. In Arizona, leaks in your attic from plumbing penetrations, electric wires, light fixtures, and building chases that are not capped off represent significant energy losses. Sealing these air leaks is a critical step to improving the overall efficiency and comfort of your home.
Small air leaks
Larger air leaks – air barrier work
Recessed light fixtures (cans)
Insulating a house attic with spray polyurethane foam (SPF) insulation on the underside of the roof deck is the best way in almost all cases to insulate and air seal an attic. This is especially true if the air distribution system (duct system) is located in the house attic. The benefits of an unvented attic with cathedralized foam insulation are numerous; more energy efficient, noticeably less dusty, much quieter and fewer insects. The downside of this approach is cost. Unfortunately, it is very expensive to remove existing insulation and then to insulate with spray polyurethane foam. For more information about this approach see our article “Spray Foam Insulation for existing homes.”
Building airtightness & indoor air quality
We adopt four strategies when performing air sealing work in our customer’s homes to help ensure that we don’t compromise indoor air quality. The first is to address potential indoor air quality problems beginning any work. We look for potential combustion safety issues as a result of air sealing and duct sealing. We look for source control issues like kitchen fans that don’t vent to the outdoors, scented candles, damp crawl space or anything else out of the ordinary.
The second strategy is to encourage the use of fresh air ventilation systems. If we are going to install a fresh air ventilation system in a house then we seal the house as tight as we can. Fresh air systems can be simple and relatively inexpensive and they can also be sophisticated and provide state-of the-art air filtration of incoming fresh air before it goes through the heat exchanger. When economy is important we use an upgraded the bathroom fan to a Panasonic fan that can be run at a very low speed 24/7. We also install fresh air ventilation systems with HEPA filtration on the for customers who are concerned about allergies.
The third strategy is customer education. Articles like this are designed to help motivated customers decide what they want to achieve in their homes. Our belief is that good information drives the decision making process.
The fourth approach is not to perform air sealing if the customer is only interested in insulation. We are happy to do this. This is what happens in the marketplace every day with almost all insulation companies. Our goal is to give customers options. We also are not interested in doing mediocre work. We are not interested in blowing more insulation in an attic when what the house really needs is air sealing and air barrier work.