How to treat oxidation on windows

Q. I live in a monastery with many windows, most of which are double-hung with aluminum screens on the outside. Those on the west side get a heavy gray deposit on the window, which I believe is due to precipitation washing through the screen. Over-the-counter window cleaners have no effect on this film. Scouring them with Bon Ami helps some, but it takes as many as five applications and a lot of elbow grease to get a satisfactory result. I judiciously tried CLR, but that doesn't help. These are double-pane thermal windows and I don't want to break or dissolve the seal between the panes or etch the glass with chemical applications. Do you know of any cleaner that is both safe and effective on this kind of deposit?

A. The stains may be a combination of airborne pollutants - especially if you are in an industrial area or downwind from one - and oxidation particles from the aluminum screens being blown against the glass. If they have been there for a while, it may be difficult to remove them. I contacted the manufacturer of Soft Scrub with Bleach and was told that it can safely be used on glass: As with any chemicals, try it first on a small, inconspicuous area. Shake the bottle well, apply it with a soft sponge and rinse it right away with clear water. IF used as suggested, it should not etch the glass surface. I have used it on many different surfaces, but not on glass, with great success.

The choice I suggest you try first is Oxy-Scrub followed by Mineral Magic. Wet the surfaces to be cleaned, sprinkle the Oxy-Scrub powder onto a very wet rag or sponge and rub the glass with it. For very tough stains, you may need to let the product stay on the glass for 10 to 20 minutes before rinsing. After you have completed the Oxy-Scrub cleaning, try Mineral Magic. It comes in liquid form ready to use. Pour some on a wet sponge and wipe onto the glass. You may need to let it stand on the surfaces for one to two minutes combined with a little scrubbing.

Try to avoid having these products remain on painted surfaces for long periods of time, as they may damage them. Wipe these surfaces quickly with a wet rag. You can order both of these products from Natural Choices Home Safe Products at oxyboost.com or by calling (866) 699-2667. I have had very good success with their products, which are oxygen-based and environmentally safe. Please let me know if these steps have taken care of the problem, as I would like to be able to recommend them again if similar circumstances arise. This is the first time I have been asked to work on such a problem, which I have done by consulting with the chemist at Natural Choices.

I need some advice regarding attic ventilation. I live in a large 12-year-old home that was build with steep hip roofs - totally inappropriate for Vermont winters as the amount of ridge vent available is inadequate for proper winter ventilation. This, in addition to a south side cathedral ceiling results in large amounts of ice buildup. I've had leaks, rot and huge icicles.

Over the 10 years I've owned the home I've used heat tapes, redone portions of the roofing materials to include storm shielding (as this was not used originally), and I still am not satisfied that I've addressed the problem properly. I believe I have to force air through the attic to achieve the least amount of melt-off. So I have come to the conclusion that I should install power roof ventilators. Do you have any recommendations? Do the solar-powered ones like those from Solar Star work?

A. I would not recommend power ventilators, as they are likely to make matters worse by drawing makeup air from the living quarters. Ventilation is an important part of roof health but there are other ways to prevent the problems you are experiencing if ventilation cannot be provided. The most important thing to do is to make sure there are no convective paths from the living parts of the house into the attic. Be very careful in that examination.

Years ago, I worked on a case where extensive rot of the rafters had occurred in an unventilated attic from a drywall tape that had separated at the peak of a cathedral ceiling; warm, moist air entered the rafter spaces and wreaked havoc. There should be no recessed light fixtures, no cracks anywhere. Seal all wall and ceiling electrical boxes with closed-cell gaskets. If there is a scuttle hole to the attic, make sure it is weatherstripped with closed-cell tape. If there is a folding attic stairway, install a specially made insulated cover for it. Make sure that all bathroom and kitchen fans are vented to the outside and not into the attic (same goes for the dryer vent).

Once you have made sure that there cannot be any convection into the attic, look into adding insulation in the attic over flat ceilings. Several inches of cellulose blown in would be ideal - don't hesitate to have 2 feet of insulation. The cathedral ceiling is another matter. The best way to deal with it is to fasten 2-inch thick extruded polystyrene or polyisocyanurate rigid insulation to the ceiling (tape all the joints) and cover it with new drywall. These steps should reduce, and perhaps even eliminate, the melting of the snow cover from heat loss.

I am an avid reader of your column and had saved the reference to a clear water seal that you recommended. But now I am not able to remember what it was or where I put the column. I have a storage shed that I covered with red cedar shakes some years ago. Originally, I coated them with a mixture of linseed oil and Thompson's Water Seal. This brought out the color very nicely; however, as you would suspect, after a few years mildew invaded the linseed oil with the resulting black stains. I removed all of the finish and stains with a mixture of Clorox and water and then pressure-washed the surface until all of the finish was removed. I want to recoat the shingles to bring out the color again and I remember you did not recommend Thompson's because it was just wax? I will not be using linseed oil this time. I would really appreciate it if you could send me the reference to the water seal you recommended.

A. My favorite coating for cedar - and other woods as well - is Amteco TWP. If you cannot find it locally in ICI paint stores, you can order it through Amteco's Web site at twp-amteco.com. Be sure to follow directions for long-term success. The best for your shed's shakes is the Cedar Tone.

Can you tell me if it is possible to install a Pergo-type floor (the kind that just snaps together) over a tile floor?

A. Yes, as long as the tile floor is in good condition. Pergo, being a floating floor installed over a special foam pad to facilitate expansion and contraction, can be installed over any smooth flooring material in good shape.

• Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Write to him in care of the Daily Herald, P.O. Box 280, Arlington Heights, IL 60006, or via e-mail at henridemarne@gmavt.net.

© 2009, United Feature Syndicate Inc.