Q: Do I need to add insulation to my existing home?

A: There is almost nothing you can do that will have as big of an impact on your home energy bills as insulation. Insulation is the ability of your home to store temperature. Just as your coat can hold in your body temperature on a cold day, insulation holds in the temperature of your house. The more you have, the better it works, and the lower your heating and cooling bills.

Figure: chart showing how heated air leaks out of your home. A third of it goes out through the floor, walls and ceilings. from www.healthandenergy.com

You spend a lot of money to heat your home. Hot air rises and leaks out of your home through the walls and every crack and crevice. As you can see in Figure 11-3, the walls, floors and ceilings are the biggest sources of leaking in your home.

Each year the amount of energy lost through un-insulated homes in the U.S. is equivalent to the amount of fuel delivered through the Alaskan Pipeline. The costs of adding insulation to your home will pay for itself in a matter of months in a mild climate and in just weeks in a severe climate.

When to insulate your existing home
For a new house, you should add as much insulation as will fit into the walls. For an existing home, adding insulation to finished walls is much more difficult.

If any of these things are true about your home, then you should consider insulating your home:

Types of insulation:
We measure the effectiveness of insulation using R-value, which is its’ thermal resistance. The higher the R-value, the greater the ability a wall can hold in temperature. Many different types of insulation are available:

Batt Insulation (R-value: 2.9 – 3.8 per inch)
Loose, fluffy batts of pink fiberglass are the most common type of insulation. Batts fit neatly between the studs of your wall framing. Unfortunately, the fiberglass is filled with chemicals and can irritate your lungs.
As an alternative, choose formaldehyde-free and recycled cotton insulation. One brand uses old blue jeans as the source of their cotton, making the insulation batts blue in color.

Loose Fill Cellulose (R-value: 3.1 – 3.7)
Dry, loose fill is sprayed into closed up walls, or into attics and hard-to-reach places. It works great for existing walls that you don’t want to open up completely. Unfortunately, loose fill insulation tends to settle like flour in a jar, leaving areas uninsulated.
As an alternative, choose natural cellulose made from recycled newsprint. It is treated with natural chemicals to make it fire resistant.

Spray in foams (R-value: 3.6 – 6.2)
These spray-in place foams are sticky and expand to fill the entire wall cavity. Although they cost more, the have a much higher R-value. Since they expand to fill every nook and cranny, they work much better at insulating your home. Avoid any foam that uses CFC’s (chlorofluorocarbons) to expand.
As an alternative, choose natural soy based foams. They are healthier and offer all of the benefits of spray foam. This is my favorite choice.

Rigid foam board (R-value: 3.9 – 7.0)
Stiff boards of insulation are used at the edges of a concrete slab, over concrete basement walls, or anywhere space is tight. They are more expensive per inch than other types, but rigid boards get a much higher R-value. Avoid formaldehyde products.
As an alternative, choose polyisocyanurate or extruded polystyrene (EPS).

Installation advice
The key to insulation is making sure it is installed properly. Make sure the insulation is not compressed, especially on the edges and around wiring. Make sure it’s in contact with the wall or ceiling, as even small gaps will have massive impact on R-value.

Location, location, location…
Insulation doesn’t just go in the walls. Be sure to remember to include insulation in these areas too:

• Attic: be sure to insulate the floor and roof of your attic.
• Foundation: more than half of your heat leaks out of the edges of your foundation slab. Insulate the edges prior to erecting the walls.
• Crawlspace: An average of 80 percent of the air in your moldy, dank, cold crawlspace will end up in your house. Insulate the floor to prevent this.
• Hot Water Pipes: adding insulation wrap to the hot water pipes is simple to do and especially important for pipes in crawlspaces.