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posted: 8/21/2012 4:34 PM

Outdoor A/C unit is OK in the sun

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Q. We moved into a fixer-upper and have been doing a lot of work to get it just right. One question I have is about our air conditioner. The exterior unit sits on the patio slab directly in the sun. There is no way to plant shrubs or anything around it, so would I be advised to build some sort of fence around it to provide some shade? Or would the unit be OK sitting in the sun by itself?

A. Many compressors are in the sun. Air blown by the fan, dissipating heat that the refrigerant has removed from air inside the house, must not be interfered with in any way. If the fan blew the air upward, a shield overhead would be restrictive. A fence would be fine, but how would it help when the sun is high and the hottest? Better to let breezes flow around the compressor.

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Some compressors discharge the hot air sideways, in which case a shield over them should be OK.

Q. Your column is one thing I always read or save for later. I want to offer alternate solutions for two of your readers.

First, instead of installing SmartVent (to provide soffit ventilation when there is no roof overhang), which sounds expensive, why not install a thermostatically controlled gable fan? The reader already has gable vents; just pick the one that would work best with the prevailing wind. If wiring is a problem, the big box stores even sell a model that is solar-powered.

Second, the elderly couple seemed satisfied with the performance of their three room AC units. Their problem was the annual removal and reinstallation. Why not have a contractor build permanent housings for them? And if one or more is positioned where it's in the sun, it would run more efficiently if the housing provided shade.

A. Thanks for your kind words and your suggestions.

I am not in favor of attic fans. They draw conditioned air from the living space because there is seldom enough net free ventilation area (NFVA) from other louvers in the attic to satisfy the fans' CFM rating.

Soffit and ridge ventilation is the best way to ventilate an attic, and it requires no energy use; the sun does it all.

Where there is no roof overhang to provide a soffit, the SmartVent is one solution, as long as the roof is steep enough to prevent a flat or negative slope on the roof immediately above the SmartVent. There are other ways to provide soffit venting on roofs without overhangs, but, in most cases, they also require alterations to the roof.

Permanent housings for the window air conditioners would require the elderly couple to uncover the units in the summer, something they may not be able to do themselves since the units may be installed on the second floor. These housings could be a source of considerable heat loss in the winter, as they cannot be made tight enough to be energy-efficient. The solution I proposed -- to install wall-mounted, ductless air conditioners -- is carefree for the couple as they age.

Q. I am a faithful reader of your column. I saw the sump pump question concerning whether it is better to have the pump work often to drain the drain tile or to set it a little higher, thus not running as often but leaving the drain tile partly full of water. I was disappointed in your answer that there is "no set rule" and in the lack of discussion of the options. Surely one way must be better than the other.

Let me ask you the question another way: Does leaving the drain tile partly full of water have a negative impact on the foundation? Or is it better to use more electricity and have the drain tile empty and dry? If there really is no set rule, and no negative impact to having a half-full drain tile, then saving electricity must be the better option.

Finally, how is your sump pump set up, high or low?

A. There is no set rule. You can choose whatever you think is best for you. If the water in the drain tiles is caused by poor grading, and if the tiles fill up after a rainfall, the solution is to correct the grading around the house to eliminate the problem. Eventually, the water will percolate in the ground. The sump in which the pump is set is seldom dry anyway, as the pump can't remove the water completely. If the sump is deeper than the outlet of the tiles, the tiles should fully drain anyway. If the outlets are flush with the bottom of the sump, there will be water in them until the soil absorbs it, and the sump will dry.

But if the water in the tiles is the result of a seasonal high water table or a spring, you could pump it forever and you'd still have water coming in until the conditions dry up, while running up your electric bill.

Footings are set on solid, undisturbed soil. Standing water in the drain tiles is not going to affect them, as most soils absorb water, whether or not there are footings.

If your last question is asking if I have a sump pump, I don't, because I don't need one.

Q. I recently had a stamped, colored concrete patio installed. I have a question about the expansion joint that is installed between the stairs and the patio. It is gray, and I was wondering if it could be painted or caulked so that it would more closely match the patio color.

A. Whether the expansion joint is made of foam, a fibrous material or cork, you can do what concrete contractors do: Apply a thin bed of Sikaflex-1a polyurethane caulking/sealant over the top to seal the porousness of the material. Let it air-cure for a few days to a week, depending on the humidity in the air. One tube should be enough. Then apply an epoxy paint on it.

You can find this product in the masonry department of Home Depot, but it is called Sikaflex sealant instead of Sikaflex-1a. You also can buy it from A.H. Harris (www.ahharris.com); some Harris stores will ship quantities as small as one tube.

Q. When you say "full-length soffit and ridge venting," does that mean that all of the vinyl soffit should be vented? Mine are in a pattern of two solid/one vented/two solid. So I would have approximately one-third vented. The soffit openings cut in the wood are, I believe, continuous. Would mine fall into the category of "continuous" soffit venting and, if not, how big of a deal would it be to change to all vented?

A. The criterion is that the total net free ventilation area (NFVA) of the soffit vents should be equal or greater than that of the ridge vent for optimum performance of this passive attic ventilation system.

Of course, the soffit and ridge vents must be installed over opened slots, a factor sometimes neglected through carelessness. If you can determine that you do not have enough NFVA in the soffits by calling the vinyl manufacturer and asking what the NFVA is of each panel, and that the variation is considerable, it should not be difficult to replace the solid panels with perforated ones.

Q. I'm currently having a large outdoor deck on my house replaced with new decking. I'm having pressure-treated yellow pine installed, and based upon an article you wrote, I'm planning to use Amteco TWP Series sealer on the deck. You recommended the Series 100 sealer, but unfortunately, that series is not sold in Vermont. Instead, they have a 1500 Series sealer.

Do you have any experience with that series, and what would you recommend? The literature on the website for Amteco advises waiting at least four months before applying the sealer to a new deck. That puts me into the winter months, so it will probably be next June before I seal it. Do you see any problems with that?

A. Amteco TWP Series 100 is being phased out slowly over the next few years in Vermont and other states because of concern about VOCs (volatile organic compounds). It is being replaced by Series 1500, which substitutes VOCs with oil. The product looks richer and somewhat darker, and it takes a little longer to dry, but it is more environmentally friendly and gives the same protection.

Amteco recommends that pressure-treated wood, which is yellow pine, not be coated with any of its products for one year to allow the excess salts in the treatment to leach out through the elements. Otherwise, the excess salts are locked in and show as "salt-and-pepper." This often requires a second application in nine months or so.

With other types of deck materials, such as cedar, it is best to wait four months to allow the weather to leach out the wood's natural oils and allow better penetration.

Q. I have decided the cracks on the crown of my chimney are too deep, and replacement is best. I've also been told the roofing material is defective. Certainteed is the manufacturer. I remember reading in your column about premature failure of this product. What is the best way to go about this procedure? What manufacturer do you recommend for replacement?

A. Since you will be replacing the chimney cap, I suggest you find a mason who will form and pour a cap at least 3-inches thick and overhanging the chimney sides by a minimum of 1 inch. It also should have a kerf on the underside of the overhang to prevent water from reaching the bricks by surface tension. If water reaches the bricks, they may absorb it and, in cold weather, they may not dry before a deep freeze sets in, which could cause them to spall (surface chunks popping off).

Certainteed was part of a class-action suit some time ago, as were other shingle manufacturers; that suit has been resolved. The early failure of asphalt-based organic and fiberglass shingles has been ongoing for decades and has affected most brands. Every time I have mentioned a brand that contractors tell me they have had good luck with, other contractors tell me they have had problems with them. So my recommendation is to stay away from the manufacturers that not only do not honor their warranties, but fight tooth and nail, including in court, to avoid honoring them.

The worst offender reported to me by a number of readers, and in my own experience as an expert witness, is IKO, a Canadian company that went to court three times to fight a legitimate claim, which the company eventually lost. It cost the shingle company a lot more in the end, as IKO had to pay the claim.

IKO's "expert" claimed that the early failure was due to the fact that the Vermont weather was too harsh for its shingles. The judge asked him why IKO sold shingles and was, in fact, the largest seller of shingles in the state.

Our own 25-year IKO shingles failed in 14 years, and, being experienced in the company's tactics, we never bothered to file a claim. We had BP shingles installed even though they, too, have experienced some early failures.

Helpful reader feedback: "I have never tried Krud Kutter for mold or wood siding, but I have been using it for years to clean my outdoor charcoal and gas grills. It works well for removing grease and oils. It does not seem to remove heavily charred gunk; I have to scrape that off the grill before using Krud Kutter. I like the fact that it is nontoxic and biodegradable."

• 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 email at henridemarne@gmavt.net. His book, "About the House," is available at www.upperaccess.com and in bookstores.

2012, United Feature Syndicate Inc.

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