DEAR SAM: I recently purchased a house that is about 85 percent completed. When I checked the attic, I found that the contractor had placed one-inch-thick insulation with tar-paper covering on one side. The house has electric heat. How can I improve the insulation?

ANSWER: I am glad that you recognize that one inch in the attic is most inadequate; I am surprised that the contractor tried to get away with it. Have you checked, too, whether he installed any insulation in the walls? I am afraid that the local electric company will hardly agree to approve the quality of insulation. Do you have a contract that states that the workmanship will be done in a good manner?

If the heating system has not been installed already and your walls are uninsulated, I would try to bargain with the contractor. Ask him to substitute a hot-air system with gas or oil. With resistance baseboard electrict year, your fuel bills may be astronomical.

Second, use batts six to eight inches thick on the attic floor. I am sure you know that the vapor barrier should face the warm side of the living quarters.

I suggest that you also ask an architect to assist you in finishing the house in accordance with accepted practices. It will be worth the 10 percent fee!

DEAR SAM: I have explored with builders in the area the possibility of having drywells installed to accommodate the water drainage from my gutters. None has been able to help me. My house is situated on a lot where the back, adjacent to an alley, is protected by a concrete wall that is about 20 feet high and 12 inches thick. It has a slight crack near a drain pipe, which is attached to one of the gutters. I feel that if I could have two drywells built, the problem would be solved. The hairline crack in the wall, too, may need repair. Whom do I call to build the drywells?

ANSWER: The location of the proposed drywells has undoubtedly deterred the builders you called; also, a pick-and-shovel laborer could have dug the drywells and their connecting trenches from the bottoms of the downspouts to the drywell tops.

Will the proposed drywells be at least five feet away (preferrably more) from the house foundation? You wouldn't want any backup water from the drywell to penetrate the foundation wall and basement. It is most important, too, that the soil surrounding the proposed drywells not consist of clay or hardpan, which will not absorb the rainwater and disperse it underground.

Perhaps you would be interested in the fundamentals of a drywell. Briefly, a hole is dug, three feet in diameter and about four feet deep; also, a shallow trench is dug from the bottom of the downspout pitched to the top of the drywell, into which a four-inch diameter bituminous pipe will be concealed. The hole will be filled with large rocks to about eight inches from the top; asphalt paper will cover the top and the input pipe. Some soil will be replaced over the asphalt paper, the balance may be spread or hauled away. See the Yellow Pages, under "Mason Contractors."

DEAR SAM: My two-story house has screened vents around the perimeter at the soffit. The crawl-space attic floor has six inches of Kraft paper-faced, fiber glass insulation. Last summer in attempting to cool the attic, I installed a thermostatic roof fan, and, several weeks later a 30-inch thermostatic ceiling fan from the hallway to the attic, where a small hatch is also located. This winter I noticed a number of wet areas in the attic at the perimeter sheathing, some of which had frosted over; also, some small icicles at the tips of nails that had penetrated the sheathing subsequently melted with warmer weather. Is more insulation indicated?

ANSWER: Your roof, with its total perimeter venting, appears to be a "hip type," as differentiated from a "gable type," which would have permitted cross-ventilation by means of gable louvres.

Your ventilation was undoubtedly improved during the summer with a cooler attic, too; however, you did not utilize the fans for the winter, although the roof fan was available for assistance to the soffit vents. An eight-inch roof "opening" near the ridge was inadequate and resulted in the wet areas and the icicles. Some attic warm moisture did escape through the ceilings causing the visible conditions specified. Stapling aluminum foil to the rafters should eliminate the problem; however, leave roof-fan vent and soffit vents open. The hatch opening and ceiling fan should be covered with similar six-inch fiber glass with vapor barrier facing living quarters; during the summer, the insulation at the ceiling fan is removed for its operation.