Heat rises. This simple concept has brought us innovations such as the chimney and the hot air balloon. Yet it’s also one of the sources of our biggest energy costs every year, as heat from your home or business is depleted throughout your attic. This heat loss is part of why 50-70 % of your home’s energy costs are tied up in your HVAC system. Don’t think that it’s limited to cold parts of the country, however. Heat gain in areas where air conditioning is a major part of your utility costs is just as big of an issue. Even worse, 90% of homes have insufficient attic insulation, leaving the homeowner open to high HVAC costs. Part of the issue, though, is having the right insulation in place. How do you know what will work best for you? This easy guide will help you find the right solution for your attic’s needs.
Do I have enough?
The first step is to determine whether your attic has sufficient insulation. Get into your attic and look at the insulation to determine the type, then measure the depth of the insulation. You’ll then want to calculate what R-value that will give you and compare that to how much insulation you need in your area. This will help you figure out whether you need to add insulation to your attic.
What kind of insulation will work best?
Here’s a quick look at different types of insulation you may want to use in your attic:
- Spray foam: Though it has a slightly higher initial installation cost than other types of insulation, closed-cell spray foam is the gold standard in insulation, especially if you’re dealing with areas that are too narrow to reach the right R-value with other insulation products. Why?Polyurethane spray foam averages R-6.5 per inch. If you have to insulate the old farmhouse with 6-inch oak rafters, you can still achieve an R-39. Whereas the same space with other insulation types would not exceed R-19, you get double the insulative value in the same amount of space. It also expands into cracks and gaps, creating a better seal from the outside.
- Batting: This is one of the most common types of insulation used, as it is easy to install and requires no special equipment. It can be made from fiberglass, mineral wool, natural fiber or plastic fiber. It comes in specific widths and is placed between studs or rafters. If you have plans to finish your attic into additional living space, using batting on the rafters is a great option to consider.
- Blow-in: This type of insulation can be fiberglass, mineral wool or cellulose. If you use cellulose, make sure it has a mold retardant — to prevent mold and mildew problems if it gets damp. If your attic already has loose insulation on the floor, you may be able to add more blown-in insulation on top to bring it up to the level it needs to reach. Unfortunately, blow-in insulation tends to settle, making it less effective as times goes on.
- Sheet foam: If you can add insulation when re-roofing, sheet foam is a great option. It has the same higher R-value as spray foam, but doesn’t require extra equipment to install it. Though it’s tempting to cut sheet foam to place in rafters and walls, it’s difficult to do this correctly. If there are any gaps around the foam, hot air can leak to your roof decking, causing moisture and ice problems. This is a problem that insulators sometimes see when homeowners do the insulation themselves — without understanding the overall system.
As you can see, attic insulation is an important part of your home’s overall energy efficiency. If you add insulation to your home’s attic, don’t forget to seal around protrusions through the roof or side walls, such as wiring, pipes or vent stacks, and remember to insulate areas that cross between your home’s heated and unheated areas, such as pull-down attic stairs.
Speaker, author, building scientist — Stephen Davis has been in the insulation and construction industry for 30 years. He is currently the North American Product Manager – Insulation Systems, for Accella Polyurethane Systems, LLC. Davis is involved with product management, product innovation, and providing building solutions to internal and external clients.
U.S Department of Energy, Insulation Fact Sheet
Insulation Institute, How Much Attic Insulation Do I Need?
U.S Department of Energy, Savings Project: Attic Stairs Cover Box