I think I’m finally ready to do something about adding to my attic insulation. How do I begin and how much do I need?
– John P. Arnold, MO
The cold weather is bringing many questions such as yours. Checking your attic insulation for the correct R-factor is easy to do, and adding additional insulation is also easy.
With a flashlight and tape measure, go in to your attic and measure the depth of the insulation. If it is a loose fill cellulose, you multiply the depth of insulation by 3.5. So, if your depth is 8”, you have an R-factor of 28. Iif you have a fiberglass batt (fiberglass that has been rolled out), multiply by 3.2 per inch. So, if you have rolled fiberglass insulation, and it is 8” deep, your attic has an R-factor of 25 (3.2 x 8). Most experts would recommend having an attic R-factor between 40 to 50.
If you need to add more insulation, there are basically two types of insulation to choose from. One is to use a loose cellulose type, which requires a blower (and is usually rented free with a certain number of bags of insulation). However, this also requires a second person to help with the blower. The other type of insulation that is readily available is the fiberglass batts. This type can be done with one person.
If using the loose cellulose, the blower is placed outside and a hose is run through the house up to the attic, where someone will be dispensing the insulation as it comes through the hose. The person outside has the job of filling the hopper with the insulation. If you are wanting to increase the R-factor of your attic by 20, you’ll need to add about 6 inches more. The person in the attic does need to be careful of distributing the insulation in an even method, so that there aren’t any raised piles. They also need to be sure not to get the insulation too close to the perimeter, where gaps are needed for proper air flow.
If you’re going to use the fiberglass batts, be sure to use the “unfaced” insulation. This is the type that does not have a Kraft paper on one side. This paper serves as a moisture barrier, but since you already have one on the insulation when the house was built, adding a second barrier will only collect moisture, so be sure NOT to use the fiberglass insulation which has one side with Kraft paper. Laying the batts down is simple, but be sure to lay them perpendicular to the existing rolled insulation, or across the floor joists. In both cases, be sure to wear long sleeves, have a respirator mask and gloves, along with some sort of utility knife (if using the batts).
After adding insulation, you will probably notice the difference is the summer as well as the winter. There are many other things you can do to seal your attic and home, but this will help the most.
Time: About 4 hours for an average attic
Materials: Gloves, respirator mask, utility knife, proper insulation (and blower if needed), flashlights or light stand, measuring tape.