It doesn't matter if you have a brand new house, most attics are under-insulated, and it is costing you money. The Michigan Uniform Energy Code only requires the builder to put R-30 insulation in the attic. The U.S. Department of Energy recommendation for our area is R-49.
You can easily determine the R-value of your attic floor by inserting a ruler down one of the floor joists and measuring the depth of the insulation. At right are the Department of Energy's approximate R-values for existing insulation. The measurements include settling.
If you decide to install the insulation yourself, you can use fiberglass batts or blow in loose-fill cellulose or fiberglass. Most people install batts because it is very easy and the exact R-value of the fiberglass batt is listed on the package.
The Owens-Corning Web Site, www.
owenscorning.com, can give you a great deal of helpful information on fiberglass batt installation and determining the amount of insulation you need.
Your current insulation is between the floor joists in the attic. It is important to fill up the space between the top of the old insulation and the top of the floor joist. Apply the next layer of insulation perpendicular to the first layer. The final depth for R-49 fiberglass batts will be about 16 inches.
When adding insulation, always buy insulation that does not have a vapor retarder. If you are adding insulation for the first time, buy the first layer of insulation with a kraft-paper vapor retarder and install it kraft-paper side down. This stops moisture from rising from the house and damaging the attic.
Insulating an attic
Materials needed: Fiberglass batt insulation; attic vents or baffles; spray foam to seal vent penetrations through attic floor; plywood to lay over joists to create a temporary floor for you to kneel on.
Tools needed: Work light; tape measure; utility knife; straight edge; lightweight, squeeze-type stapler; putty knife or shim for pushing insulation into place; work gloves; loose-fitting, long-sleeved shirt; OSHA-approved safety glasses; disposable dust respirator; long pants; hat; and boots.
1. Install temporary lighting and plywood flooring. Then carry the insulation you will need for the first layer up to the attic. Do not unwrap the insulation until it is in the attic.
2. Begin installing insulation at the outer edges of the attic and work toward the center. Unroll the insulation in place and cut to fit. Do not compress batt insulation because it reduces the R-value.
3. Install the second layer of insulation perpendicular to first layer.
4. Install attic vents or rafter baffles to assure the free flow of air from the soffit vents upward. Secure the vents in between the rafters.
5. Keep insulation 3 inches away from hot lights, chimneys and flues. Insulation can be snugged-up to recessed lights labeled "I.C." Insulation must be cut and stapled to keep it 3 inches away from all other lights and hot objects.
6. Stuff empty spaces around chimneys with pieces of unfaced insulation. You're done. You just saved a bundle of money.