Q: In the attic of our ranch house we have blanket insulation on the floor. It is getting moisture in it even though we recently put on a new roof. This moisture is showing up in the outside corners of the bedrooms below, and mildew is spreading over the walls behind the furniture. The house has no basement, just a crawl space. Can you suggest where we can look for the cause of this condition? R.S., Millville, Pa.

A: Assuming that you have no actual roof leaks (unlikely if the roof is fairly new), chances are that the moisture in the attic insulation is caused by condensation. There are two things that should be done: First, make certain there are louvers or other vents in the attic, above the insulation, which allow for free circulation of air under the roof at all times. These louvers should be large enough to provide at least one square foot of free opening for every 300 square feet of attic floor space. Second, make certain the crawl space is also ventilated in the same way, and that the firt floor (if unpaved) is covered with roofing felt or polyethylene sheets.

Q: I live in a ground floor apartment and would like to block the view of passersby without shutting off the light by pulling my shades all the way down. Can window shades be mounted upside down - that is, near or on the sill so that they pull up instead of down? C.M., New York City.

A: Yes, they can, and this mounting method is not at all unusual. You would have to buy ceiling brackets instead of conventional outside brackets, then mount these to the sill, upside down. A piece of cord, like a Venetian blind cord, is then attached to the shade instead of the usual handle or pull, and this is run up to a little pulley which is fastened at the top of the window frame in the center. The cord comes down from the pulley so that pulling down on it you raise the shade from the bottom.

Q: Thirty years ago we laid linoleum over plywood which had been nailed down over an old kitchen floor. The lineoleum has now worn out and we want to put down new lineleum or vinyl tiles. Floor men tell us we must lay new plywood on top of the old linoleum, then put the new floor covering on top of this. This would result in a build-up floor that would necessitate trimming off doors. Can't we just remove the old linoleum, sand the glue off the plywood, then put new linoleum on this? W.E., Beford Hills, N.Y.

A: I can see no reason why an extra layer of plywood would be required. You should be able to scrape the old linoleum up by using a stiff scraper and soaking the cement underneath with hot water. It should not be necessary to get every bit of cement off, nor to stand the plywood. Just get most of it off, then put down a layer of felt (a kind of heavy paper used under floor tiles) before laying either linoleum or vinyl, Use linoleum paste to put the felt down and use the adhesive recommended by the manufacturer for the floor covering.

Q: Our 12-year-old house has asbestos shingles on the outside. They have never been painted and we have gotten conflicting advice about whether or not they should be painted. Do you advise painting, and, if so, what kind of paint should we use? R.R., Matawan, N.J.

A: Asbestos shingles do not have to be painted, as far as maintaining them is concerned. People do paint them, however, purely as a matter of esthetics - that is, becaues they get dirty looking, or because they want a change of color. As a rule, an alkyd or latex base masonry paint works best, but be sure you follow directions on the label as to the type of primer or surfacer conditioner recommended for use on asbestos shingles as a first coat.

Questions about home repair should be sent to Home Repair Clinic. The New York Times, Times Square, New York, N.Y. 10036. Only those questions of general interest will be answered in this column.