Q: My home was built in 1960 and it’s not insulated. It is in Alameda, Calif., near San Francisco. It’s one story, has stucco on three sides and has an unusual wood front. Is there any insulating material available that can be applied to the exterior of a house and is not too expensive? What is the best type of insulation for the attic?

A: We’re not aware of any stand-alone insulation product for application to the exterior of a home. If you were planning to re-side your house with vinyl or aluminum siding, it is installed with a layer of insulation between the new and old siding. But new siding is expensive and, we think, not very good looking. If the goal is simply to insulate the house, we don’t recommend it.

Short of re-siding, exterior walls can be insulated by boring holes at the top and bottom of each stud bay and blowing insulation into the cavity. The finished result will look OK on the stucco (after it’s patched), but the front of your house will have visible wooden plugs.

The San Francisco Bay Area climate is temperate. Because cost seems to be an issue, we suggest you forgo insulating the walls, and concentrate on insulating the attic and weatherstripping around doors and windows instead. It will give you the most bang for your buck.

Installing attic insulation is a do-it-yourself job. All you’ll be out is the cost of materials and a little of your time. We suggest you use craft-paper-faced fiberglass batt insulation with an R-38 rating. Install the craft paper toward the conditioned area, the inside of the house. To determine how much you’ll need, simply multiply the length of the house by its width. This figure is the square footage of the floor space and the attic above. Insulation is sold in rolls with square footage of coverage on the packaging.

Your ceiling joists are either 16 inches or 24 inches apart. Insulation is sold in these widths. Simply roll out the insulation and fit it between the attic joists, making sure to cut around any pipes and electrical wires that may be in the attic. Batt insulation may be cut with a utility knife. Try to keep the number of pieces to a minimum.

Making sure exterior doors are properly weatherstripped will reduce the cold air entering the house, keep you warmer and reduce the amount your heater will have to work. Both weatherstripping and batt insulation are available at home centers. We think if you take these simple steps, you’ll be a couple of steps closer to being warm as a bug in a rug for the rest of this winter and into the future.

Q: In a previous column you recommended removing old existing craft-paper R-13 insulation before installing new poly-encapsulated R-19 insulation. What do you recommend, and why, for insulating roof/upper-floor crawl space that had insulation blown in (circa 1985)? Can we simply place poly-encapsulated batts over the blown insulation? Or, like the old craft-paper R-13, should the blown insulation be removed?

A: The reason we recommended removing the R-13 craft-paper-faced insulation before installing poly-encapsulated insulation is to avoid stacking vapor barriers, resulting in condensation and possible mold growth. In your case you can go one of two ways. Since the blown-in insulation has no vapor barrier, you can either blow in another layer of insulation or you can roll out non-faced R-38 insulation over the existing insulation. No need to remove the blown-in material that you have. In any case we don’t recommend the plastic encapsulated insulation for your application.


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