Air sealing is one of those confusing topics that sparks a lot of debate. Is too much sealing a bad thing, something that could be detrimental to indoor air quality? Or should buildings be sealed as tightly as possible to prevent air leaks and save on energy costs? Proper sealing can definitely reduce energy costs, which passes on major savings to homeowners—and, there are ways to mitigate indoor pollutants so that indoor air quality isn’t an issue. Let’s take an in-depth look at what air sealing means, common sealing strategies, and some weatherization specifics pertaining to Boston homes!
What is Air Sealing?
To put it simply, air sealing is the process of stopping drafts. This is done through lots of different strategies, from upgrading insulation to sealing around windows and doors. Weather stripping, caulk and foam insulation are common ways to close up drafts, which tightens the building’s thermal envelope. The process is designed to keep conditioned air where it belongs—cool air indoors in the summer, and cool air outside in the winter.
Does Air Sealing Trap Indoor Pollutants?
Good sealing can trap indoor pollutants. However, this doesn’t mean that builders should deliberately allow drafts or weaken the building’s envelope. Rather, if indoor air quality is an issue, then sources of the pollutants should be sought out and eliminated. This means if there are unvented heaters, then proper vents should be installed for them. Another common pollutant is water vapor, particularly in kitchens and bathrooms. This can cause mold problems and other issues, but excess moisture can easily be mitigated with exhaust fans and other venting solutions.
Common Air Sealing Strategies
Homes are notoriously full of places for air to escape. Whether the project is new construction or a retrofit of an existing home, there are dozens of places to check for potential air leaks, and each of these areas has its own best solution for stopping a potential leak. Here are some of the places to check as well as strategies to prevent leaks!
- Attics: Attics are often one of the major sources of air leaks within a home, and that is because not only does heat tend to rise and escape through the attic, but there are plenty of places for heat to make its escape—around chimneys, through poorly sealed soffits and so forth. To make sure an attic is properly sealed, it helps to create a checklist. Not only will you need to make sure that the space is well insulated, but you’ll need to use spray foam or other materials around chimneys, vents, electrical boxes, the attic hatch or access panel and elsewhere.
- Rough Openings for Windows and Doors: When windows and doors are drafty, the problem is often because the rough opening wasn’t sealed properly. Fortunately, even if this is a retrofit project, it’s a relatively easy fix. Simply remove trim and use spray foam to fill in the gaps between the opening and the window’s frame.
- Leaks around Pipes: This is another common way for air to escape, and it’s another easy fix. Here, you can use spray foam to fill in gaps around pipes or conduit. In moist areas or around pipes prone to sweating, use caulk instead.
- Exhaust Fans: There are a couple of considerations for exhaust fans. The first is the case itself, which should be sealed with metallic tape or caulk to prevent leaks while the fan is in use. Then there’s the opening for the fan, which should be filled with spray foam to prevent additional leaks.
- Whole House Fans: These are popular ways to vent excess heat and humidity, but they’re also a potential source for air leaks. To ensure fans don’t leak air when not in operation, they should come with a couple of important features. Covers for the fans should be gasketed, and the covers themselves should be insulated to at least R10 to help minimize loss of conditioned air. As with any indoor-to-outdoor fixture, you’ll also need to take care to use spray foam or caulk around the fan’s frame to prevent leaks there, too.
- Weather Stripping Doors and Windows: Whether on new installations or on a job to stop leaks in existing doors and windows, weather stripping is key. It should be sturdy enough to withstand things like friction and seasonal temperature changes as well as the wear and tear caused by the opening and closing of the fixtures. For different doors and windows, you’ll need different types of weather stripping, but when installed properly, it can save homeowners up to 20% on heating and air conditioning yearly.
The Mass Save Program
In Massachusetts, there is a program that can help homeowners tighten up air leaks at little to no cost. If you want to recommend it to clients, it’s called the Mass Save program. This program offers home energy assessments to search for areas in need of air sealing, and if leaks are found, then some sealing is provided to the homeowner at no cost. Learn more about the program here!
As you can see, air sealing is a complex process with lots of places throughout a home that need to be evaluated for leaks. But, it’s a worthwhile process that will end up saving the homeowner lots of money on energy costs!