Sensible Home: Tips for insulating garage, basement walls
Dear Jim: Our family is growing and we need more living space. I plan to convert our garage into a bedroom and build a carport. What is the most efficient way to insulate the masonry garage walls?
– Monica H.
Dear Monica: Converting an existing space in your house into living space is far less expensive per square foot than making a room addition. Since you are not starting from scratch, it takes more planning to make it energy efficient and comfortable for all types of weather.
Whether you are converting a garage or a basement, which also is a common project, the wall insulation techniques are similar. Since the underground temperature stays more constant than the outdoor air temperature, you may need less insulation thickness for a basement-to-bedroom conversion.
The major difference when insulating is the flow of water vapor through the insulation. In all but the most humid climates, vapor flows from indoors to outdoors for above-ground walls and from outdoors to indoors for a basement. This impacts which side of the insulation should have the vapor barrier.
Before you begin your project, get quotes from some contractors about making the conversion for you. Many companies have predesigned insulated wall and ceiling systems specifically designed for this purpose. It may not cost as much as you think as compared to your buying all the materials.
Conversion systems with insulated fabric-covered panels are ideal for a bedroom or home theater where sound is a concern. Ones with a snap-in vinyl attachment system are good for moisture resistance. Also, the panels can be snapped out at any time to gain access to the block or brick walls.
The easiest way to insulate the walls yourself is to build 2-by-4 studded wall framing on 24-inch centers and insert fiberglass batt insulation. For your garage, staple the vapor barrier to the studs. The only drawback to this method, particularly if your garage is small, is you lose floor space. Use pressure-treated lumber where it touches the concrete floor.
In order to save floor space, attaching thinner furring strips to wall and insulating with rigid foam insulation is another option. It has higher R-value per inch thickness. Rigid foam insulation panel are available which are designed to fit over the strips. When using rigid foam insulation, it must be covered with drywall, not just paneling, for fire safety.
Although walls are an important area to insulate, as is the attic, don’t forget the floor. A chilly concrete floor can make the entire room feel cold and adding carpeting may not be enough. Install breathable-type resilient panels on the top of the concrete before the carpeting.
The following companies offer wall insulation materials and systems: Certainteed, (800) 782-8777, www.certainteed.com; Champion, (888) 847-5705, www.acousticwallsolutions.com; Dow Chemical, (800) 441-4369, www.dow.com; Johns Manville, (800) 654-3103, www.jm.com; and Owens Corning, (800) 438-7465, www.owenscorning.com
Dear Jim: I try to use my window fan at night instead of the window air conditioner. I was wondering if it is more efficient to run the fan on low speed instead of high because it uses less electricity on low?
– Roger D.
Dear Roger: You are better off running it on high speed for a shorter length of time. This will allow you to wait to turn it on later when the outdoor air has cooled down more. Run it on low after the room is cool.
If your area is very humid, it may be better not to use the window fan if you air-condition during the day. Bringing that humidity into the house may make your air conditioner run more in the morning and cost more overall.
Send inquiries to James Dulley, The Forum of Fargo-Moorhead, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit www.dulley.com