Q: I recently spoke with an insulation contractor about insulating my 100-year-old house with a sprayed-on foam. Somewhere around R-40 is the recommended insulation for this area, but he said that his product's R-14 was sufficient. I never got a clear answer from him as to why that would be so, but it seemed to revolve around the fact that his product seals rather than just insulates. Do you have any information on this stuff, or know who else to talk to? --Marshall B.

A: There is a difference between insulating a building and sealing it, so the contractor is correct in that regard. However, I sense he is also making some misleading and overblown claims about his product.

With standard blown-in fiberglass attic insulation, bits of fiberglass are blown into place with air. The loft of the fiberglass/air combination creates millions of tiny air pockets, which in turn slows down the movement of heated air from the house and helps keep that heat from being lost and therefore wasted.

Another part of any good home weatherization package is to seal against air infiltration. Homes that are drafty waste heat by allowing warm air to escape to the outside, and also allow for air movement inside the home that greatly affects how comfortable the occupants feel. Sprayed-on foams such as what you describe are wonderful for sealing air leaks, since they expand to seal the tiny cracks and crevices in a way that fiberglass insulation doesn't (nor is it intended for that purpose). Foam also has air pockets trapped within it as it expands, and is a very good insulation product. However, in both cases - with the foam and with the blown fiberglass - as the products compress over time some of that insulation value is lost. This is often more of a problem with expanded foam then it is with the fiberglass.

R-value, which indicates how well a material resists the passage of heat through it, is a consistent, calculated value. So when the building codes require R-38, that means R-38, whether it's from fiberglass, foam boards, sprayed foam, or any other material or combination of materials. And while the foam does offer some definite sealant properties that will contribute to a warmer home, that certainly does not account for an additional R-14 in insulating value.

I would suggest that you contact whichever local utility company supplies the fuel you use as your primary heating source - electricity, gas, etc. They can provide you with a wealth of information about weatherization and insulation, and can assist you further with what will work best for your home and who the reputable local insulation contractors are. They can also typically arrange to do an energy audit on your home to show you other ways besides just insulating that you can save fuel and improve comfort, and that is something I would highly recommend having done - especially on a 100-year-old house.

One final thing. I'm a little uncomfortable with the claims being made by this contractor, so if you choose to proceed with this hiring this company, I would verify all their license information; ask for and speak with references of other homeowners they have worked for in your area; ask for specific information on how long the energy savings for your home will take to pay back the investment in their product (make sure this is specific to your home, not a generic statement); ask for specific guarantees in writing of what their product does and how long it will last without a significant decrease in R-value; and finally ask for documentation for the building department as to how their product meets current building codes.

Q: My wife and I want to put a film on the windows of our house, but what we've seen look like the ones that go on your car, with all the little bubbles in it. Can you suggest something better? --John W.

A: There are literally dozens of different types of tinting films available, depending on what you want to accomplish. Some films are used to block heat from coming through the window in warmer climates, while others are used to keep heat in the house in colder climates. Films can be used to lessen UV rays to protect furniture from fading, or they can be used to provide privacy by keeping those on the outside from looking in while those on the inside can still look out.

Your best bet would be to contact a local glass company and discuss the various options with them. They'll be able to either do the work for you or recommend someone who can, and most will sell you the materials if you want to undertake the project yourself. As to the bubbles you saw, that is typically the result of either poor preparation or poor installation - or both. Window films are not particularly difficult to apply, but you need to make sure the glass is clean and not too hot, and you need to carefully follow the manufacturer's instructions.

Incidentally, some types of film can trap so much heat in the glass that it can damage the insulated glass seal, and thereby void the warranty on the window. Be sure and discuss this with the glass company when selecting film for your particular installation.