A: There are a couple of things I can suggest for that drafty vent. Since you said this is an interior wall, I am assuming the vent goes up into the attic. Before you get going with any insulating, check in the attic to verify that the vent goes all the way through to the outside of the house. If it terminates within the attic space, take the time now to vent it to the exterior to prevent a buildup of moisture within the attic itself.
Vents such as this do not carry a lot of heat, so it's safe to insulate it inside the cabinet. My preference is to enclose the duct pipe with rigid foam insulation, available from any home center - 1-inch thick material will be plenty. Simply cut the foam board to size with a sharp utility knife and a straightedge, and friction-fit it around the pipe. This will also take care of any drafts. If desired for appearance sake, you can then build a simple box from 1/8-inch- or 1/4-inch-thick finish-grade plywood inside the cabinet, which will cover the foam.
Q: Someone once suggested that I could sprinkle Tide on my fiberglass roof shingles to control moss. I've been doing that for several years with good results. Is there any evidence that this will do long-term damage to the roof, such as loosening the granules? – Don D.
A: Since bleach is an oxidizer, it is effective at killing mildew, moss and mold. Therefore the Tide you've been using will certainly work against the moss, as will any other laundry detergent or other cleaner that contains bleach.
I am not aware of any detrimental effects to the roofing from the detergent itself, other than the possibility of discoloring the shingles. However, if you are using a heavy spray or trying to brush the shingles with a push broom or other brush, you can dislodge a lot of the granules and cause the shingles to fail prematurely.
A couple of other things to consider: Depending on the manufacturer, you may be voiding their warranty by washing or otherwise "treating" the shingles, so you might want to check with them as well. Also, large quantities of detergent can harm landscaping and possibly be detrimental to wildlife, and some communities also have regulations against soap being directed into storm drains, sewers, or other public areas.
Wherever possible, take whatever action you can to reduce the causes of the mildew and moss. Keep trees trimmed back, keep gutters clear and flowing properly, and keep leaves and pine needles from building up on the roof.
Q: In one of your recent columns, you addressed the problems associated with pressure washing cedar decks, and I also seem to remember you advising against pressure washing to remove paint. We have a 73-year-old house that needs repainting and I have to remove the peeling paint first, but now I'm a little concerned about using our pressure washer on it. What do you advise? --Ken F.
A: Like a lot of people in the construction industry, I have changed my thinking somewhat on the value of pressure washing compared with the potential problems associated with it. The use of high-pressure water in very concentrated streams – which is what is necessary to remove loose paint – can do some substantial damage to the underlying wood, especially on a 75-year-old house. I still feel pressure washing is okay for removing surface dirt prior to painting, providing you use a wide nozzle pattern that is not focusing too much of the water's pressure in any one spot, and that you allow the wood to dry completely before painting.
As to my best advice for preparing your old siding for new paint, it unfortunately comes back down to elbow grease. You should scrape off any loose paint with a paint scraper, taking care not to gouge into the wood, then sand the raised edges of the remaining adjacent paint to smooth them down and help the new paint to blend in better. Depending on the type of siding you have, you might also be able to use a belt or random orbit sander to do the entire job. Again, be careful not to sand too heavily into the wood. After the scraping and sanding is complete, I would strongly recommend spot-priming the bare wood, then applying another coat of primer over the entire wall prior to painting.
One strong word of caution here: With a 73-year-old house, there's a strong chance that you have one or more layers of lead paint. Be sure and have the paint tested for lead before doing any scraping or sanding.
