How to Insulate a Loft Crawl Space


Insulating an attic crawl space will help maintain a consistent temperature in your home and will also help lower heating and cooling bills. This is more important if you plan to covert this unused space into usable living space. It’s not hard to do even if the area is not readily accessible. Here’s how to insulate a loft crawl space.

Step 1

Figure out how much insulation you have in your attic crawl space by measuring its thickness. If your attic crawl space doesn’t have insulation yet, skip to step 2. If there is insulation in your attic crawl space and it is in good condition, you can simply add more insulation as needed. Use the guidelines in the next step to determine how much insulation you need.

Step 2

Figure out how much insulation you will need. Insulation is these days measured by its resistance to heat movement and rated with the letter “R” and a number after it. For example, an attic crawl space with 12 inches of quality insulation would be given a value of R-30, whereas 6 inches might have a value of R-15 (heat will travel through 6 inches of insulation two times as fast as 12 inches). It is recommended that you use R-30 insulation (or higher) in your attic crawl space. It is important to note that different brands of insulation have quite different R ratings. Visit the site listed in the resources below to determine how much padding you need for your attic crawl space.

Step 3

Decide if you want to insulate the attic crawl space with loose/blown insulation (cellulose, fiberglass, rock-wool or cotton) or batting (cotton or fiberglass). Using a rented blowing machine to install loose insulation may be easier if the crawl space is hard to reach. Batting has to be precisely cut and fitted to maximize insulation effectiveness.

Step 4

Remove any stored objects from the attic crawl space.

Step 5

Make note of vents or electrical cables that might be in the attic crawl space (carefully install insulation around them).

Step 6

Lay down a polyethylene moisture barrier on the side where the warmest air will be. This means the moisture barrier should be on the bottom of the attic insulation if you heat your home most of the year, and on the top if you run your AC most of the year.

Step 7

Install the insulation in the attic crawl space by using the blowing machine or carefully cutting fiberglass batting and placing it between the joists.

Step 8

Take extra care when installing insulation near vents or electrical cables and leave about 3 inches between any potential heat source and your layer of insulation.

Tips & Warnings

Don’t compress the insulation when installing it – compressing it will only reduce its effectiveness.

Check out the resources below this article for more information on how to lower your heating and cooling bills and related projects.

Always wear face protection when installing insulation. This means wearing goggles, a face mask, gloves and clothes that cover all exposed skin.