Insulating Crawl Space is Good Way to Save on Energy Costs

Q: Due to an extreme mold problem caused by a faulty plumbing installation, all flooring and subflooring are being removed from our 60-year-old house. Therefore, it is time to insulate the crawl space, which has never had insulation.

Is there a preferred type of insulation you could recommend? Our climate is mild central coast California with winter lows in the upper 20s and 30s.

A: With energy prices on the rise, it would be a good idea for all homeowners to consider adding insulation and sealing air leaks that allow conditioned air to escape from the living areas.

Before you replace the floor system, the perimeter walls of the foundation need to be insulated to an R11 or R19. The higher the R number, the more resistance to thermal transfer the product possesses.

I found an excellent U.S. Department of Energy Web site (www.ornl.gov/~roofs/Zip/ZipHome) that instructs you to enter your ZIP code and information about your home's construction and energy systems. The site will then calculate recommendations for insulation of

the attic, walls and foundation. This is valuable information that can dramatically increase your energy savings. You can then select the type of insulation you want to use.

I would recommend you consider Icynene, a spray-on expanding foam insulation for the foundation's perimeter walls (www.icynene.com). Icynene is water- and mold-resistant and should be installed by a qualified contractor.

If you choose to do the work yourself, I would recommend rigid extruded polystyrene panels, which are lightweight and can be cut with a crosscut saw and applied to the foundation walls using an adhesive or by nailing to the sill plate. Foundation vents should be sealed to prevent air leakage and humidity problems, however, you will need to provide conditioned air to the crawl space.

A heating/venting/air-conditioning contractor (HVAC) can show you how to properly condition the crawl using existing ductwork or with a small fan installed in an opening in the floor.

Also make sure to remove all debris and vegetation from the crawl space, then cover the soils with a 6-mil vapor barrier. A recent innovation, Clean-Space, encapsulates the walls and soils with a heavy 20-mil vapor barrier, which prevents moisture migration and radon gas from entering the crawl space environment. The CleanSpace approach is expensive, but it is preferred in place of a standard vapor barrier.

To locate air leaks, wait for a windy day, then use the smoke from a lighted incense stick to check the interior openings of windows and doors, attic doors, and electric outlet and switch openings on exterior walls. Sometimes the leakage is so apparent that you can feel the air flow with your hand.

Caulking and self-adhesive weather strips are an economical and easy to use to seal unwanted air leaks. Home and hardware stores can provide you with rubber gaskets that fit behind the face plates of outlets and switches.

If you have older, single-pane windows, consider window replacement, selecting energy-efficient double-paned windows, or install storm windows if that fits your budget. The point is to do something now, because energy prices are only going to get higher. The days of cheap energy are behind us.

Send e-mail to C. Dwight Barnett at d.barnett@insightbb.com.

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