Home Energy Savings Series: Wall Insulation
If you feel as if your house is never quite as warm as you’d like and you’re not sure why, the answer may lie behind your walls. Inadequate insulation for walls can be a key reason your energy bills are higher than you’d like. ENERGY STAR® says properly insulating walls can also help reduce outside noise; decrease pollen, dust and insects entering your home; lower the chance for ice dams on roofs; and help with humidity control.
Ideally, your home has a continuous barrier of insulation, from your attic all the way down to your basement and including all your interior and exterior walls. A coat, after all, isn’t as effective if it’s not zipped. Until the 1960s, though, standard wall insulation codes for homes did not really exist. This means that if you’ve got a home built before then, chances are good that your exterior wall insulation or interior wall insulation might be inadequate or even nonexistent if you live in a really old home.
Insulation is basically a coat for your house: It slows the flow of heat, ideally keeping more of it where you want it — either inside when it’s colder outside, or outside when you’d prefer not to melt in your home. Like a coat, the thicker (generally) the insulation, the warmer the house in the winter. A down parka is warmer than a thin fleece, right?
Before you decide whether or not you need to add exterior wall insulation or interior wall insulation, you’ll want to take a few other steps. Check for air leaks (which could include some easy DIY fixes to your leaky home). An energy audit makes sense, too, since that can illuminate other places where your home is letting energy escape.
Assuming you’ve determined a need for insulating walls, here’s what you need to know to get started.
How to look for adequate insulation for walls
While you are looking behind your walls to determine how much interior wall insulation or exterior wall insulation your house currently has, David Darling offers this plan to check your wall insulation in his Encyclopedia of Alternative Energy:
- Check the walls next to an unheated space such as a garage or basement. Often insulation is exposed in spots like these so you can easily see the types of insulation and measure how much exists.
- Check exterior wall insulation.
- Turn off power to the electrical outlet.
- Remove the outlet cover and shine a flashlight into the crack behind the outlet area. You should be able to see interior wall insulation.
- Pull out a small piece of insulation so you can see what type of insulation your house has and measure its thickness.
- Check a few selected outlets upstairs and downstairs. Wall insulation in one part of the house does not mean your entire house is insulated.
- Check and measure insulation in any crawl spaces. The thickness will help you determine the R-value.
Types of wall insulation
Now that you’ve got a sense of how much insulation your walls have, you’ll need to consider types of insulation and pay attention to R-value as you decide how to insulate walls. R-value is a number used to explain how much heat flow is restricted by a certain type of insulation. Different R-value levels are required for different parts of your home but basically the higher the R-value, the better your insulation. Energy.gov has a handy chart to see what kind of R-values your home should ideally have in different climate zones.
We have focused on how to insulate walls for existing homes rather than how to insulate walls on a house under construction, under the assumption that if you’re building a new house, you’re working with a contractor and architect who are going to inform you about best practices for insulating walls. Energy.gov recommends the following types of wall insulation for insulating walls:
- Spray foam wall insulation: Spray foam wall insulation can be used to add or increase the amount of insulation in existing walls, making it ideal for existing homes. It can be applied using small spray containers (if the space is small) or in larger quantities. The foam in spray foam wall insulation expands after it is sprayed into or on cracks, creating airtight barriers. Foam insulation comes in two forms, Energy.gov says: closed-cell and open-cell. Closed-cell, considered the most effective of the spray foam wall insulation options, has cells that fill with a gas that ensures the foam expands more completely. Open-cells are not as dense and are filled with air. Foam insulation can expand to 100X its volume, home renovation expert Bob Vila says, noting that the addition of spray foam wall insulation is a home improvement that will both pay back over time with lower energy usage and increase a home’s potential market value.
- Blown wall insulation: This form of interior wall insulation is great for existing walls and hard-to-reach places, and is blown in using special equipment. It can be made of rock or slag wool, fiberglass or cellulose.
- Block wall insulation: Concrete block wall insulation is generally foam board that is placed on the inside of the wall in existing homes to beef up interior wall insulation. An unfinished basement, for instance, might be a likely candidate for this type of insulation.
- Cellulose wall insulation: Cellulose is one of the materials commonly used in loose-fill or blown wall insulation. Cellulose wall insulation works well as existing interior wall insulation and can be used in hard-to-reach places or wall cavities. It’s generally blown into place.
So now you know more about insulating walls, including the types of insulation to use. Don’t forget the rest of your house’s “coat.” We’ve got you covered for attic insulation and basement insulation, too. We also offer insulation for light switches and outlets, a good starting point for insulating your walls.
