What are the easiest, most affordable ways of insulating a crawl space?

Insulating a Crawl Space

Insulating a Crawl Space

I've been trying to do some remodeling of an older house, and I hope you can help. I have some crawl spaces underneath the house in order to get underneath for any kind of work that has to be done. Is there anything that can be used to put on bottom of floors to help keep the inside floors warmer? I've heard about spray-on insulation or regular insulation, but I'm not sure about these.
Linda P.

Advice from Retired Contractor on Insulating a Crawl Space

As a retired contractor, I have seen various methods in insulating under floors in crawl spaces. In doing this myself, I found two methods that will work and save you from "eating" the insulating contents and getting it in your eyes.

The first method uses the insulated aluminum faced board that air condition companies use to make their ductwork from. A 4 x 8 sheet can be cut with a razor, utility knife and straight edge. When cutting, make the pieces two inches wider than the space between the floor joists. Then with the straight edge in place, cut a one-inch strip that is one inch wide along each side of each panel on the long side, usually eight feet. Do not cut through the aluminum facing, but from the insulation side, leave just a one-inch aluminum strip on the sides to fasten to the joists with a staple gun, aluminum two-inch tape or cross pieces of other materials. This is a two-person job with one outside cutting the panels and the other under the crawl space relaying measurements and fastening ready panels passed to them. Tape the joints.

The second method uses two- to three-inch thick Styrofoam panels from any supplier. Cut panels by checking the inside dimensions of the spaces between the joists and cutting as described in method one. Cutting them 1/2 inch wider than the inside measurement allows the installer to force the panel tightly between the joists by "wedging" them in place. After putting in place, two-inch tape can seal any gaps that may exist. The foregoing methods may not provide the R Value of rolled bat, paper insulation, but they will save your eyes, keep you from breathing fiberglass, and help you avoid the aggravating work of trying to make roll insulation "stay put."

Please remember that you must use safety goggles and a safety rope to go to your partner outside in case of emergency. Also, use a face mask to keep from breathing airborne particles of insulation. (Glass fibers FLY!)

Keep Floors Warmer and Pipes from Freezing

Quite a few years ago, we would often have frozen water pipes in our crawl space in the winter. My husband used the sheets of solid Styrofoam that are two inches thick to insulate the crawl space walls. In most cases, he measured and cut the Styrofoam and was able to get a tight fit without nailing anything. I have found this to keep my floors warmer in the winter, and it has stopped the pipes from freezing as well.
Denise from Nebraska

Lay Down Plastic Sheeting

We have a sand crawl space under our kitchen. Laying down plastic sheeting on the sand, as a vapor barrier, helps keep our floor warmer. It was not very expensive, but itís very effective.
Elaine in NJ

Is It Worth Doing Yourself? Do the Math

Yes, you can put any insulation on the bottom, but I'd suggest leaving it to the professionals. However, if you're determined, using cans of insulation spray can be done at a high cost. Do the math and decide which is more cost effective, and then call a recommended professional in your area.

Safety First

My crawlspace insulation is fiberglass batting, the same stuff used between studs. It's held in place by coat-hanger-weight wires between the joists every few feet. The wires are just a bit wider than the space and are just held in place by tension. If you go this route, you'll be crawling around on your back reaching up, so be sure to wear safety glasses to keep the fiberglass out of your eyes. In addition, I have a vapor barrier under the house (giant sheet of heavyweight plastic).

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