How to insulate an attic

Household 2 min read

Properly adding insulation to your attic can help make your home more comfortable by keeping it cooler in the summer and warmer in the winter. Plus, it can reduce energy bills and make your home eco-friendlier. When the sun beats down on your roof in the summer, the insulation is a barrier between the sun’s rays and your home. During the winter, it helps prevent the heat inside your home from escaping.

There are several different types of insulation from which to choose. We asked Valli Moore, president of RBH Insulation, about the different kinds and which one she thinks works best for an attic.

What are the different types of attic insulation?

Batt or Blanketed

This type of insulation comes in large pieces, usually 16 or 24 inches wide and 3.5 to 12 inches thick. It’s typically made of fiberglass, and you lay out the pieces between the floor joist beams to insulate the attic.


Blown in insulation is available in fiberglass and cellulose, made from ground-up newspaper treated with a fire retardant. It’s made up of millions of tiny particles that you pump into the attic with a blower truck.

Spray foam

Spray foam insulation is like shaving cream — you spray it, and it expands. It’s used often in new construction but not as much in existing homes.

Rigid board

This type of foam board fits between the framing joists. However, Moore says she would never put rigid insulation in an existing attic.

What’s the best insulation for an attic?

Moore works in Southern California, where there are two main types of insulation contractors typically use in an existing home: fiberglass (either blown-in or batts) and cellulose-blown insulation.

Moore recommends the blanket or batts insulation if there’s a leak, electrical problem, or something else the homeowner needs to repair. “With blanket insulation, the blankets can be lifted away, the repairs can be done, and the blanket can be put back,” she says.” With cellulose or blown-in, you’ve got zillions of little particles that need to be moved away for those repairs to be done.” If you plan on hiring a contractor, check out our list of important questions to ask a contractor before you start.

How much insulation do I need in my attic?

The amount of attic insulation you need depends on the size of your attic. To calculate the right amount for your attic, you must determine the area of the space. If your attic is 1,000 square feet, you’ll need 1,000 square feet of insulation. If it’s 750 square feet, you’ll need 750 square feet of insulation.

If you have an older home, it’s a good idea to understand what attic insulation previous contractors might have installed. Materials like asbestos, which contractors routinely use for insulation, can be a safety risk in older homes. Learn more about how to test for asbestos in your home and how home insurance may cover asbestos removal.

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