Install foam board under weather-resistant barrier
Q. I live in Schaumburg and plan to reside my house this summer. The house was built in 1985 with 2-by-6 exterior walls. There is plywood on the exterior corners and Celotex sheathing covered with Tyvek between the corners. When I install new siding, I plan to cover the Tyvek with ¾-inch blue insulating foam board and vinyl siding.
My concern is trapping moisture between the foam and Tyvek, even though Tyvek is not a vapor barrier. Is this a proper way to cover the old Tyvek, with foam and siding? Or does the Tyvek need to be on the outside of insulating foam board?
Via e-mail
A. The best way is to put the foam board underneath the Tyvek so that the Tyvek can prevent any water that will get behind the vinyl siding from wetting the substrate. However, that means that you will have to remove the Tyvek and install a new one after the foam board has been put on. That's hardly worth it. There is really no risk at installing the foam board over the Tyvek. Blueboard (Styrofoam) is impervious to water absorption, and the only risk is that water can get between the boards, which is unlikely if you use tongue-and-groove boards and install them tongue up.
Q. Am I overly concerned about using my fireplace since its conversion from oil to gas heating in 2005? I had all the required inspections following the completion of the work. A liner was installed in the chimney. I had used my fireplace for the 29 years that I have lived in the house and would like to resume using it. Are there any safety factors I need to consider?
South Orange, N.J.
A. I am confused here. If your fireplace has its own flue and the heating system has a separate one, why are you concerned about the safety of using the fireplace after the conversion? Your main concern should be that the flue be cleaned thoroughly after your oil-fired heat is converted to gas-fired heat, as the composition of the combustion gases from oil and gas is very different. Failure to have the chimney cleaned can result in an oily run-off down the chimney. But since a liner was installed in the chimney (I assume the heating system vents into the lined flue), there should be no concern about the conversion.
One safety factor is the new liner for the gas-fired heating system's cap. Make sure that the top of the fireplace flue is not equipped with either a flat or tunnel-type cap that has the ability to direct the fireplace's gases toward the heating system's flue under certain wind conditions. If your house is reasonably tight, one of the flues can become the conduit for your house's make-up air when the heating system is firing or the fireplace is used, creating a negative pressure in the house. The flue servicing the fireplace should have no cap and be lower than the new liner servicing the heating system, or it should have a tunnel-type cap that is perpendicular to the other flue or there should be a divider, known as a wythe, between the two flues to prevent the gases from one from entering the other.
Q. My factory-painted steel overhead garage doors were recently vandalized with graffiti that has since been removed. However, I still have discolored streaks on each door. What type of primer and paint should I use to restore them back to their original color?
Via e-mail
A. You can use any of the stain-killer primers, such as ZINSSER's Cover-Stain, Bulls Eye 1-2-3 or similar products from other manufacturers. Follow with a latex paint of your choice.
Q. Can you tell me if there is any use for used coffee grinds?
Via e-mail
A. You can compost them or use them as a deodorizer for a refrigerator or freezer. That's all I can think of. Other readers may offer other uses.
Q. We would like to have a few cast cement-block retaining walls built this year. Some of the walls I see are beautiful, and some develop a white stain on them, which is very unsightly. I think the stain is efflorescence. Is this due to the brand of the block, Versa-Loc, Keystone, Allen Block, etc.? Or is this due to how the product is installed? I have seen houses next door to each other, and it appears they have the same band of block, yet one is perfect and the other is stained. These walls are not cheap, and I don't want this problem to develop on mine. The walls we are considering are to be no more than 30 inches high.
Manor, Pa.
A. You are right; it is efflorescence, and it occurs as the salts in the masonry are dissolved by water and brought to the surface of the blocks. The salts are left there when the water evaporates. Efflorescence is easy to remove with a dry, stiff bristle brush. If this does not remove the efflorescence completely, you can use a wet brush or wet the blocks with a garden hose.
Q. I read your column frequently and recently learned that you don't always advise using waterproof paint on basement walls. I had an addition built five years ago with great attention to drainage and exterior sealing. The 14-by-40-foot concrete-block basement was to be a workshop/storage area with a half bath. My intention was to paint the walls for moisture and appearance. However, I'm having second thoughts after reading your response. The area has an exterior French drain as well as drain pipes under the concrete slab leading to a sump pump. It has been bone dry for five years and is aided by the heating vents from a gas hot-air furnace. If these conditions still suggest not painting the walls, what other options would you suggest to improve the appearance?
Via e-mail
A. The reason that I do not recommend waterproofing concrete block walls is because I've seen several examples of water buildup within the cores of the blocks when improper grading or other external factors allowed water to penetrate the foundation blocks. This led to disastrous problems.
You can paint the walls with a non-waterproofing paint, as it will fail if moisture gets inside the blocks' cores, and the basement will leak. Considering what measures were taken to ensure a dry basement, you are probably safe.
Q. We are having a problem with moisture in our second-story attic. Our house is located in Western Pennsylvania. It is a two story; the ground floor is constructed of concrete block with 2-by-4-inch furring strips and 3½-inch insulation in the walls. The second story is standard wood framing with 2-by-4s. We have no basement; we're on a concrete slab with 2-by-4-inch joists sitting on the slab and fiberglass insulation with a vapor barrier. The attic has 6 inches of fiberglass insulation with the proper vapor barrier. There are perforated panels in the 1-foot overhanging eaves, a ridge vent and vent panels on either end of the attic gables.
The original 900-square-foot core of the house was built in 1978. In 1997, we put an addition of 650 square feet on the house and a 650-square-foot garage. The gable ends of the house are facing east and west, with the front of the house facing south.
Our problem is with condensation in the second-story attic and what appears to be mold on the underside of the plywood sub-roofing. We've lived here for 26 years and didn't have a problem until the last two to three years. Prior to that, we had a forced-air heating system, which was replaced with a boiler system and radiators three years ago.
What suggestions do you have to eliminate the moisture in the attic and to stop the growth of mold? I have purchased two ventilation fans with temperature and humidity controls on them; one for the second-story attic and the other for the garage attic. No condensation has formed in the garage attic.
Cabot, Pa.
A. It appears that the change in your heating system is the culprit. Warm-air heating was probably keeping your house drier. And considering your house's age, it was probably getting its fresh air through the many cracks and avenues within the exterior envelope of the house, which renewed the air within the house with drier exterior air every time the furnace came on.
The new boiler you have must certainly be the type that provides its own make-up air through a dual or separate vent, which does not bring fresh air into the entire house and, in turn, increases the humidity. The great majority of attic-moisture problems are due to the convection of warm, moist air from the living areas into the attic. This is the first thing that needs to be looked at. These convective paths can be holes through which wires and pipes go through the ceiling or wall plates to get into the attic; separating gypsum board tape; attic access panels or disappearing stairs that have not been weatherstripped; recessed-light fixtures; bathroom fans, etc.
If you are handy, you can get into the attic, look for wires and pipes, and foam the holes around them. You can also install closed-cell gaskets under all electric covers of every switch and receptacle on the inside and outside walls. The surest way to find all these convective paths is to have a blow door test made, but you may not want to undertake such an expense. If you are installing the fans through a vent or a gable wall, they may aggravate the problem, as they can draw moist air from the house, unless there is enough net free ventilation area to satisfy their CFM output. On the other hand, if you are setting them free on the attic floor, they may force cold attic air into the living quarters and increase your heating costs. Once you solve the convection problems, the mold will die and should no longer be a problem.
© 2008, United Feature Syndicate, Inc.