| Insulation and Air Quality |
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Most of us know what it's like to sit in a drafty, uncomfortable area of a home, like around windows or doors. And some of us may have noticed how stuffy our homes can get when we keep the windows closed for the entire winter or summer. But you may be surprised to learn that these two problems, drafty and stuffy, are likely related. A properly designed and installed insulation system combined with air-sealing techniques, which seal gaps and openings, can minimize drafts and uncomfortable spots. When a home is sealed tightly to keep out drafts, however, the air can feel stuffy and stale.The solution is to install a ventilation system to help keep indoor air fresh and clean. A good balance between insulation, air sealing and ventilation contributes significantly to how comfortable you and your family are inside your home, how energy efficient your home is and how good the quality of the indoor air is. If you're having a home built, be sure to talk to your builder about how they're addressing this critical balance.
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Insulation bundles a home up against the elements, so that you and your family can stay warm in winter and cool in summer.
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Insulation: A Home's ClothesPart of the solution to a drafty home is proper insulation. Homes stay warm in winter much like people do -- both need heavy clothes covering all their exposed parts. Insulation, a home's clothes, should be placed in all areas that face the elements, including the foundation, exterior walls and the roof. (These three areas combined make up what's called the building enclosure.) Not having insulation in one of these areas is similar to wearing a coat but no gloves. We'll talk more about insulation basics and types in upcoming articles. Features and Benefits of Air Sealing Another solution to a drafty home is air sealing. There will be openings in the building enclosure for windows, doors, outlets, pipes and any other component that needs to come in through your wall. The insulation stops around these openings, leaving small gaps in the building enclosure. Air can leak in and out of even the smallest of gaps. Not only does this air leakage lead to uncomfortable drafts, but it can also reduce the energy efficiency of your home. If cold air leaks into your home in winter, you'll need to turn up the thermostat to stay comfortable, which makes your heating system run more often and for longer periods of time. This results in more energy use and higher energy bills. So, not only does the building enclosure need to be well insulated, it also needs to be well sealed around openings and at joints and connections so that air doesn't leak in or out. To keep heated or cooled air inside the home and to keep outside air from entering the home, the insulation in your home should be sandwiched between interior and exterior air barriers. Different materials can serve as an air barrier. For example, the main internal air barrier of homes in cold climates is drywall, because it is the most continuously applied material, covering exterior walls, ceilings and floors. The external air barrier can be one of two materials: - Housewrap.
- An Exterior Sheathing, like foam board or oriented strand board.
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Expanded foam sealant around windows stops air leaks.
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Both materials need to be sealed at the joints and connections to prevent air and moisture from leaking in. For an air barrier to be completely effective, it must be continuous, meaning there are no gaps or openings through which air can leak in or out. But, as we said earlier, you have to make openings for windows and doors in exterior walls, and any gaps or seams those openings create need to be sealed. The construction materials commonly used for air sealing include expanded foams, foam strips, weatherstrips, weatherproof tape and caulking. Following are some instances in which these materials are used:- Expanded foam around windows and exterior door jambs.
- Foam sill sealer between foundation wall and sill plate.
- Weatherstrips around the edges of windows, doors and attic hatches.
- Caulking or foam strips between floor sheathing and bottom plate.
- Caulking or expanded foam to seal holes cut in top and bottom plates and floor joists for wiring and plumbing.
The Importance of Ventilation in an Insulated and Air Sealed Home In a well insulated and sealed home, you should be cozy and comfortable. But because there isn't much air leaking in and out of the home, you could be feeling a little like you're living in a bubble, without fresh air. That's why many homeowners are electing to have a ventilation system installed. A ventilation system lets in fresh air while pushing out stale air and moisture (from kitchens and bathrooms, for example.) For more information on ventilation, see the "Don't Forget About the "V" in HVAC" article in our "Home IQ" package.
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Power-assisted combustion appliances, such as this water heater, contain a fan to help exhaust combustion byproducts to the exterior of the home.
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Another aspect of the home that can affect indoor air quality is a combustion appliance. These are appliances like water heaters and furnaces that use natural fuels, such as gas or oil. As a general rule, it's important to stay away from naturally vented combustion appliances, which draw air from inside the home to burn fuel and rely on a home's natural air pressure to remove the combustion byproducts. In a tightly sealed home, it's easy for naturally vented combustion appliances to backdraft, which happens when byproducts from a combustion appliance are pulled back into a room rather than pushed outside. Byproducts from a combustion appliance may include water vapor, carbon dioxide and sometimes deadly pollutants, such as carbon monoxide. Backdrafting occurs when the air surrounding the appliance is depressurized. (Pressurization relates to the air pressure, and is beyond the scope of this article. For our purposes, we'll say that depressurization can happen in a home, and can cause backdrafting, which is why it's important to stay away from naturally vented combustion appliances.) To prevent backdrafting, avoid naturally vented water heaters and furnaces, and ventless fireplaces. Ask your builder instead to use power-assisted or closed combustion water heaters and furnaces, and direct-vented fireplaces. Power-assisted combustion appliances contain a fan to help exhaust combustion byproducts outside of the home. The Relation Between Insulation, Air Sealing, and Air Quality Like a person's parts, a home's parts are related to each other. For example, your eyes and brain work together to translate the images you see on your computer monitor into something you understand. In a house, the insulation system is related to air sealing and ventilation, which affect air quality. So changes a builder makes (or doesn't make) to one system can positively or negatively affect how the others work. Be sure to talk to your builder about the following: - What measures are being taken to air seal around windows, doors and other openings.
- Whether a ventilation system is being installed, and what the additional costs are if it's optional.
- Whether power-assisted combustion appliances are being installed.
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