Watch Out for Barriers Between Sidings

Question: Our house has wood siding, and we are thinking of covering it with vinyl siding because of paint problems (chipping, checking, alligatoring, etc.).

However, we have heard some disquieting rumors about vinyl--that the house would not "breathe"--whatever that means. Please comment about this subject.

Answer: There's been a lot said about covering wood siding with vinyl or aluminum, and, indeed, there have been problems in some cases in which moisture collects inside the exterior walls of the house and causes deterioration.

Eric Hahn, manager of Alcan Building Products, 1641 S. Sunkist St., Anaheim 92806, says the problem has been in installations that used a vapor-barrier insulation between the old and new sidings that would not allow the water vapor from the inside of the house to escape. The escape of this water vapor is what many refer to as "breathing."

Homeowners especially concerned about energy conservation were the most likely to have installed insulation with a vapor barrier between the two sidings, thinking they were doing right in preventing outside cold or hot air from entering the house. Actually, they were creating a water trap, which ultimately caused problems.

"Houses generate an incredible amount of water vapor," Hahn says. If the interior of the house has a vapor barrier properly installed--that is with the plastic or foil directly behind the dry wall and next to the living area of the house--much of the water vapor is dissipated through the heating system or air conditioning. Some, of course, escapes through the soffits under the eaves of the house and by other routes.

It's Hahn's belief that most houses in Southern California do not have vapor barriers in the walls. Therefore, when a homeowner decides to cover wood siding and puts a vapor barrier between the old wood and the new vinyl or aluminum siding, the inside water vapor penetrates the wood siding and is trapped there, resulting in warping and dry rot and any number of other problems.

There are many kinds of insulations that are "wrong" for installation between siding, Hahn says, such as plastic-coated products or solid foam.

"These products might be fine for other purposes, but the key here is finding the right product for this particular job," the Alcan manager says. He praises a Monsanto product called Fome-Cor, described as extruded polystyrene foam with weatherproof kraft paper on one side, while the other side is faced with foil that has pin-size perforations all over it (which allow "breathing.")

To meet the ICBO (International Conference of Building Officials) codes on insulation between the sidings, a product should have a 5 perm rating, Hahn says, and Fome-Cor has a 7.5 rating.

As for Alcan's vinyl siding, Hahn explains that it has weep holes at the bottom as further safeguard against accumulated moisture.

If you'd like some literature about siding manufactured by Alcan Aluminum Corp., the parent company of Alcan Business Products, write Hahn at the address above and send a stamped, self-addressed business envelope. He points out that Alcan siding has a lifetime warranty for the homeowner who installs it. The warranty extends to subsequent owners up to a total of 50 years from the time of installation.

Q: We recently bought a fixer-upper and don't have the money to do all the fixing right now. One of the rooms that will have to wait about two years is the kitchen. I'd like to do something "funky" with the old cabinets. Any ideas?

A: A quick and easy cover-up would be pre-pasted vinyl wallpaper. Cut rectangles of it, just an inch or two smaller than the cabinet doors and drawer facings. Wet and apply the wallpaper in the recommended way (being careful to line up the pattern from one unit to another). Prepaint a thin molding and glue or tack it around the edge of the wallpapered area on the doors and drawers. If the paper you choose has matching fabric, you can complete the decor with curtains to match.

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