Furnaces, damp basements, and attic insulation

Q I am considering replacing my present oil-fired furnace in my hot water heating system. Where can I obtain unbiased information regarding comparative efficiencies of oil-burning units?

Robert W. Baber Dover, Del.

Whew! We contacted five places seeking an answer to this query before we landed on our feet with a response from Gas Appliance Manufacturers Association, PO Box 9245, Arlington, Va. 22209.

See Pages 34 and 37 for residential oil central furnaces and residential oil boilers respectively in the 57-page booklet called Directory of Certified Furnace and Boiler Efficiency Ratings, April to October 1983. The association's phone number is (703) 525-9565.

Q We would like to recommend the partitioning of an area in our church basement so as to form several new rooms, but before the proposal is presented to the membership, we believe the basement should first be free of dampness. The basement walls from the floor up to about two feet are now so damp that paint will not adhere to them. A fan and dehumidifier accomplish little. How can we control the moisture problem?

A church decorating committee Pompton Lakes, N.J.

How to deal with damp basement has been the most frequently asked question in this column aside from exterior peeling paint. Happily the problem lends itself to a relatively easy solution.

We used to advise readers to remove the earth from the outside basement walls to a point below the footings, install a footing drain to ''daylight,'' hot-mop a waterproofing asphaltic product on the exterior basement walls below grade, and then fill back in with earth.

Although feasible, this is obviously an expensive and ponderous solution to waterproofing a basement.

One of our readers offered a far simpler answer to the task. The best part was that the job could be done from the inside because his firm guaranteed that the walls would inhibit moisture migration or penetration if the directions were carefully followed and the substrate was sound.

To be successful, however, there could be no short cuts. The company is Sealwall Products, Inc., 36300 Lakeland Boulevard, Eastlake, Ohio 44094. The phone number is: (216) 951-3445.

Other companies offer competing waterproofing products. Ask your local hardware or building-supply store.

The Sealwall product meets the Army Corps of Engineers specification TTP-0035 , which requires 80 percent use of fresh dry cement, and calls for applying two or more coats of its cementious base product which seals the wall from the inside. The process includes an important hydraulic cement cove where the floor joins the walls. Paint may then be applied to the thoroughly dried overlay.

Our advice: Insist on using only waterproofing materials and methods which meet the federal specification.

Q I want to add insulation to my attic, which now has 2 to 3 inches of uneven insulation between the joists. A builder tells me not to add loose fill but rather roll batts with the vapor barrier facing down across the joists. Do you agree? Would unfaced batts make any difference?

Ken Swanson Chicago

I suggest you get in touch with a reputable insulation contractor instead of a mere builder on insulation matters. We builders are general contractors, but not as expert in specific trades as are our subcontractors.

Insulation methods, thicknesses, and materials, because of temperature and humidity extremes, may vary among geographical areas. A pat answer on the Arizona desert would not be suitable in a damp, cold climate along the shore of Lake Michigan.

Retrofitting an existing attic with additional insulation calls for special awareness. I'd get in touch with your local building department for an on-site inspection and written recommendation.

Then draw up particular insulation specifications. Ask for two or three written bids from local competent insulation contractors.

You may be entitled to a tax credit for the added insulation. Check it out.

For answers in depth regarding vapor barriers in your particular area, contact the Mineral Insulation Manufacturers Association, Springfield Avenue, Summit, N.J. 07901.

If you have a question on designing, improving, or maintaining your home, send it to the real estate editor, The Christian Science Monitor, One Norway Street, Boston, Mass. 02115.