Insulation may not sound like the most exciting topic. But if lowering your heating and cooling costs while being more comfortable at home is something that grabs your interest, it’s worth taking a few minutes to review the basics of home insulation. With a little know-how, you can assess your home’s insulation yourself and determine if you could benefit from an upgrade.
How Does Insulation Conserve Energy?
Insulation creates a thermal barrier that helps your home hold onto the treated air coming from your HVAC system. Heat is always trying to move from warmer areas to cooler ones, which means that it’s infiltrating your home in the summer and escaping in the winter. This effect of thermal energy cannot be stopped entirely, but with sufficient insulation, it can be dramatically slowed. The end result is that your HVAC system runs less often, reducing what is usually the single largest energy expense in the home.
Does My Home Have Enough Insulation?
The answer not only depends on the type and amount of insulation you currently have, it depends on where you live. The colder your climate, the more insulation you should have.
The U.S. Department of Energy offers insulation recommendations across eight different climate zones. Just find your zone on the map and refer to the information below for guidelines on insulating attics with little or no insulation, floors, uninsulated walls and insulated walls.
These recommendations are stated as “R-values” — an important standard of measurement when making insulation upgrades. The higher the R-value, the more effective the insulation.
R-values vary based on the type, density and thickness of insulation. When you’re shopping for fiberglass batts, for instance, you’ll see R-values like 11 for 3.5-inch-thick batts and 25 for 8-inch batts because the batts don’t vary in thickness. But when it comes to insulation like blown-in cellulose fibers, you’ll need to first calculate the amount of cellulose it takes to reach your target R-value, and then install the insulation to that depth.
In order to perform these calculations, look for the R-value per inch of the various insulation materials you’re considering. R-values per inch range from about 3.1 to 4.3 for most materials, including fiberglass batts, mineral wool and blown cellulose. Denser insulation types like polyurethane blocks and spray foam insulation can have R-values per inch in the 5.5 to 6.5 range.
If you plan to use a single insulation type, just divide your recommended R-value by the R-value per inch of your chosen material to find out how many inches you need in each area. You can also use multiple overlapping insulation types by calculating their R-values separately and adding them up to reach your recommended R-value total.
What Type of Insulation Should I Use?
Each type of insulation has its own advantages. For some insulation projects, there’s one type that’s clearly better than the rest. For other projects, there may be several comparable options and the choice may come down to the cost or difficulty of installation.
Most common insulation types:
- Batt insulation: Batts are like thick blankets, and can be made of fiberglass, mineral wool or other fiber blends. It’s popular because it’s cheap, effective and easy to install, especially between the rafters in an attic floor.
- Blown-in insulation: This type consists of small, loose shreds of cellulose, fiberglass or mineral wool. As the name implies, it’s installed using an air pump and large hose that blows the insulating material into every nook and cranny, making it ideal for adding insulation to finished walls and hard-to-reach areas.
- Spray foam insulation: Professional installation of this insulation type is expensive compared to others, but it provides superior R-value per inch and is especially durable. Spray foam is also a superior choice for sealing air leaks.
- Rigid block insulation: Most insulating blocks are made of foam board or polyurethane and provide R-values per inch superior to batts and blown-in insulation. But because they’re rigid, they’re often impractical for adding insulation to existing structures. They’re ideal for installing in new construction.
Now that you know the basics, you can check out the insulation on your attic floor and even add more on your own as a DIY weekend project. But for a whole-home assessment that includes the hidden insulation in your walls, you’re often better off retaining the inspection services of an installation professional.