Two Options Available to Insulate Walls of Crawl Space, First Aid for the Ailing House uexpress

Two Options Available to Insulate Walls of Crawl Space

by Henri de Marne

Share on Facebook Share on Twitter Print Article

Q: In the winter in the Chicago area, the coldest room in our house is the family room. The house has a basement, but only a crawl space under the family room. I have wrapped the heating ducts with insulation. What kind of an R-value insulation should I use on the crawl space walls? The walls are cement. How do I fasten the insulation to the walls? — Illinois, via email

A: There are two ways to insulate crawl space walls.

Whichever method you choose, first insulate the band joists. The easiest way is to cut R-19 or higher fiberglass batts of the right width (16 or 24 inches) one inch bigger than the depth of the floor joists to ensure a tight fit. If you choose unfaced fiberglass, carefully staple 6-mil plastic over the insulation on all four sides.

One method is to insulate with rigid foam insulation, but make sure that the concrete walls are clean by brushing them off with a large stiff bristle brush.

Apply walnut-sized dabs of polyurethane caulking compound or Styrobond every foot or so to the concrete walls and adhere 2-inch thick XPS rigid insulation panels of whatever size you can get into the crawl space to the walls by pushing hard on them.

The other method is to staple R-19 fiberglass batts to the mud sill (member onto which the joists are set) and drape them down to the soil, which needs to be thoroughly covered with 6-mil plastic in any case. It is best to cut the batts about one foot longer than the distance to the soil, bend the batts over the plastic floor cover and hold them in place with bricks or whatever is heavy enough to do so.

Crawl spaces whose soil is covered with plastic do not need vents. Vents allow cold air in the winter and unwelcome moisture in the summer. They should be closed and insulated.

If you leave the basement access to the crawl space open, some of the basements heat can also help.

Q: In looking at installing ceiling exhaust fans in our bathrooms, my contractor recommended Panasonic models. I see that it markets an Energy Recovery Ventilators (ERV), model FV-04VE1, and I would like to know if you have an opinion on them. My intention would be to use them in conjunction with a condensation sensor, such as their model FV-WCCS1-W — and, of course, the extra ductwork.

At 0.8 sones, its going to be very quiet, but it circulates only 40 cubic feet per minute and quite pricey — more than twice the cost of its 80 cfm ceiling fan with built-in humidistat.

The bathrooms are on the second floor of a two-story house in Massachusetts. Each bathroom is just under 70 square feet, with typical ceiling heights.

Is there a compelling reason to go with an ERV, and if so, can you recommend a more economical solution? —Massachusetts, via email

A: ERVs are very helpful and desirable for whole-house ventilation. They condition the air being brought into the house while exhausting conditioned air in both summer and winter. They do save energy.

However, they are not worthwhile for small bathrooms. You would never recover the initial capital investment in energy savings.

The use of bathroom fans is to remove excessive humidity, and that can be done more economically with a simple, quiet fan ducted to the outside through a gable wall. If the fan is controlled by a timer, it will shut off automatically in the time chosen.

A bathroom fan with a humidistat requires seasonal changes to account for the changes in RH (relative humidity). Otherwise, it would run constantly in the other season from which it was set. It is not worth the expense.

Q: We have been snowbirds for the last four years and really worry about our 1857 Cape Cod for the four months we are away. Weve had friends look in on it occasionally, but we still worry. What is the best way to winterize a home? We have an oil furnace, which runs year-round. It is serviced every year, but is probably 15 years old. Thank you. — Vermont, via email

A: Since you run the furnace year-round, set the thermostat to 45 degree Fahrenheit and install a warning system that will telephone several people who have agreed to be in charge of notifying your HVAC contractor and have a key to your house.

You can find such alarm systems on the following websites:;;;

Another way is to have a licensed HVAC contractor winterize your home. He or she will make sure that the clothes washer, dishwasher and all fixtures are properly winterized.

If your heating system is warm air, there is no need to do anything else, but if it is a boiler and you have a hydronic heating system, antifreeze can be added to it, but its efficiency will be somewhat reduced.

But I would be hesitant at shutting off the heat completely, as some of your furniture and other possessions may be damaged by the cold. Although there are many vacation houses that are winterized and left without heat for the entire winter, such homes may not have possessions that are susceptible to harm.

Leave a Reply