Q: Is it true that a wood-burning fireplace wastes more heat than it provides? If this is true, does this mean only when the heating system is actually running?

A: There are a number of variables to consider in answering your question. As a rule the typical open wood-burning fireplace wastes more heat than it adds to the inside if it is used while the central heating system is working at the same time, and if the outside temperature is below a certain level. The air that goes up the chimney of the fireplace carries a great deal of indoor air that has already been heated by the furnace.

Although conditions will vary, the "turnaround" point for a typical home is when the outside temperature drops below 20F -- above this the fireplace will provide a slight heat gain; below, there will be a net loss of BTUs from inside. Having the thermostat set very low while the fire is burning will help, and if doors can be closed to seal off the room (you will have to open a window to provide air for the fire), this will also help.

Q: We are planning to make a year-round room from our porch and as part of this project we have installed 3 1/2-inch insulation under the floor. We put the vapor barrier facing up, pushing it until it touched the flooring. We were told this is wrong, so we added a second layer of insulation with the vapor barrier facing down (toward the outside). Now we intend to staple a plastic sheet over the bottom to protect the insulation. Are we doing this correctly, and which way should the vapor barrier be facing?

A: Insulation should always be installed with the vapor barrier facing the warm or heated side, so in the case of insulation under a floor the vapor barrier should be up, facing the floor above. The only thing you did wrong was to push the insulation up against the flooring; ideally there should be airspace between the top of the insulation and its vapor barrier, and the underside of the flooring.

Since you have already added a second layer of insulation with the vapor barrier facing down there is no point in taking it down, but if you can reach up with a hook-shaped piece of wire and pull both layers down away from the flooring to leave an airspace that would help. Instead of covering the insulation on the underside with plastic, use chicken wire to support the insulation -- it won't trap moisture behind it the way a sheet of plastic will.

Q: We have a country home that we often use on weekends during the winter. We used to leave the heat on (at the lowest setting), but because of the present cost of fuel we plan to shut down the heating system for the winter and drain all water pipes and heating lines. The local hardware dealer told us that in an old house such as ours the plaster will freeze and collapse. Do you agree?

A: If the house is otherwise structurally sound there should be no drastic damage from lack of heat. The plaster may develop a few cracks but these should not be serious, and even this is unlikely (unless the plaster and wood are already in bad shape).

Q: Our newly purchased home has exposed water pipes in the ceiling of our unfinished basement. On hot summer days the cold-water pipes sweat and drip water onto the basement floor. Since we plan eventually to paint or otherwise cover this floor, the dripping problem concerns us. Is there any way to prevent it?

A: All plumbing supply outlets sell pipe insulation specifically designed to prevent problems of this kind. This is a type of foam sleeve or split tube that can be easily fitted over the pipes (it comes in all common diameters). It is sealed or closed with special clips or with special tape. Incidentally, this insulation is also a good idea on hot-water pipes that run through unheated areas -- it will help prevent heat loss in those pipes.

Q: We had vinyl asbestos tile put down on our kitchen floor a few months ago by an inexperienced person (we didn't know this at the time). Apparently he put too much adhesive on the back of the tiles, and gunk keeps seeping up between the seams. We are trying to find a remedy without the expense of picking up all the tiles. Is there any kind of clear plastic coating, such as urethane, we could apply over the tile that would seal the surface and prevent the gunk from oozing up in the seams?

A: I'm afraid nothing you could paint over the surface would stop this. Eventually all the excess will ooze out and no more will come up, but there is no way to tell how long this will take. It depends on how much adhesive was put down originally, as well as on temperature and humidity. The only other choice -- if you don't want to wait and keep wiping up in the meantime -- is to lift the tiles where this is happening and scrape off the excess with a notched trowel.

Q: We have a skylight in our upstairs bathroom that freezes and forms ice around the base during the winter. When a warm spell arrives the ice that has accumulated melts and the water runs down the skylight well onto the ceiling. We caulked the skylight, but this does no good. What can we do to prevent this next winter so we don't have to repaint the ceiling each year?

A: Your problem is condensation, not any form of leakage through the frame or around the glass (that is why caulking didn't help). About the only way to cure this condition is to install a storm window or storm sash under the skylight -- at least during cold weather. This can be a sheet of clear plastic that fits across the well or opening under the skylight, or it can be a sheet of glass that fits into a wood frame that can be taken down in warm weather. Either of these procedures will keep warm moist air (inside the house) from coming in contact with the cold glass, and thus will prevent condensation. This extra glass or plastic will keep you from using the skylight as a means of ventilation in the winter, so if this is important the storm sash can be hinged or made easily removable for opening the skylight.

Q: I have galvanized gutters around the outside of my house and every year much of the paint on them comes off. I have decided to take off all the paint and leave them raw -- no paint, no peeling. However, I am wondering if rusting will be a problem. I thought of putting on a coat of heat-proof aluminum paint. Would you recommend this?

A: Aluminum paint is still paint, and it will peel as much as any other when conditions cause peeling. If you leave the metal raw it will certainly rust in time. Your problem is that you probably did not use the right type of metal primer in the first place. Galvanized metal requires a special type of primer that must be applied directly to the bare metal. This may mean cleaning all the old paint off first. After the primer has dried, you can apply a regular trim paint or house paint to finish it off.

Q: I am doing some of my own plumbing work while altering my kitchen and laundry area, and using copper tubing for the water lines. In several places I have to bend the tubing into a curve, but I find the tubing kinks easily, instead of bending smoothly. Is there any trick that can prevent this?

A: All you need is a simple tool called a tubing bender. Resembling a long, tightly coiled spring, this gadget enables you to bend copper or aluminim tubing into a smooth curve without forming kinks. The tubing is slipped inside the hollow core of the tubing bender, then bent to the desired curve -- after which the springlike coil is slipped off. These benders come in various diameters to suit all common sizes of copper tubing and are sold in many hardware stores, as well as in plumbing supply houses.

Letters from readers should be addressed to Barnard Gladstone in care of The New York Times Syndication Sales Corp., 200 Park Ave., New York, N.Y. 10017. Questions of general interest will be answered in this column, but Gladstone regrets that unpublished letters cannot be answered individually.