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Sunday, September 1, 2002 - Page updated at 12:00 AM

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Ask the Expert / Darrell Hay

The pros and cons of ridge vents

Several weeks ago, I solicited your comments and experiences with roof-ridge vents.

I have been skeptical about their effectiveness, despite manufacturer claims.

Here are some of the responses:

• "We had ridge vents installed when the new roof was installed. They did not work, and we had to have several older-style roof vents installed. Now it is ventilated properly."

• "I recently had my home re-roofed and had a ridge vent installed. During our recent hot weather I was very impressed with how cool my home remained even into the evening when it normally stays warmer inside. The effectiveness of ridge vents surprised and pleased me!"

• "It is my opinion that the ridge vent has made the most significant improvement in the overall comfort of the house. I only use a fan when it gets above 85 degrees, and it cools down quickly. When I move, it will be the first improvement I make on any house I buy."

• "My ridge vent leaked water into the attic during high winds. I took it out and noticed no difference in the heat in the attic or inside the house. I then added round spinning vents, and it stays very cool."

• "We just installed a composition roof (replacing shakes) and a ridge vent in the process. There is little or no attic insulation. Our house and second story has never been so hot during heat snaps. The shingles are laying on new plywood underlayment; the shakes used to 'breathe' through the lateral slats.

"We had a ridge vent installed in addition to a small solar fan and eave and gable vents. The mushroom vents we used to have were removed, and maybe they were supplementing the eave vents and the gable vents just enough to really make the difference.

"I'm leaning toward putting medium-sized fans on the ends of the house where the gable vents are. I think that will supplement the solar-powered fan.

"I think the heat culprits are four things: (1) a composition roof that gets really hot during the day; (2) the half-inch plywood that holds the heat in; (3) vents that can't get rid of the heat fast enough; and (4) the solar fan that doesn't have the muscle to pull this kind of hot air.

"I think ridge vents are OK, but they must operate in conjunction with other venting options."

• "This is my first summer with a new standing-seam metal roof with ridge vents. It replaced wood shakes. I have noticed that it is much hotter much earlier in the day.

"It has a simple, one-peak roof about six feet high (from the horizontal roof beams) in the center. The only way I can explain the increased heat is the roof color. The new roof color is dark bronze. Dark metal heats up a lot faster than rotten wood shakes."

Now, my take on this:

As I see it, the real key to proper ridge venting is strictly following the installation instructions for properly balanced upper and lower venting in a pitched roof.

Nice thought, but whoever measures the "net free area" of their eave vents before installation? Never seen that done, even for new construction. You put it in wherever you can. But mess it up and you could get backdrafting with unbaffled vents.

With the emergence of composition roofs as the dominant type, the need for roof venting is ever more critical.

The thinking about the importance of roof venting is changing, too, with a shift in the understanding of how heat is actually transferred to an attic via conduction, radiation or convection.

Color and orientation of the roof, radiant barriers inside the attic, and the total surface area of the roofing product are given more weight.

One particularly memorable comment I heard recently was when someone compared a roof and attic system to a sunbather: Ventilate all you want underneath; nothing done there will prevent sunburn on top.

Q: Referring to your recent column on building codes: As an electrical-code consultant, I got a kick out of the builder you mentioned that does not "go beyond code." I think the point needs to be made that codes are requirements, not construction guidelines. I know from experience that you can build an electrical system that would be totally code compliant — but would not work. I can imagine that a similar situation could occur with building codes. Sounds like the company you were referring to was sleazy guys producing a less than acceptable product.

A: There are several codes that are patently ridiculous, and others that contradict each other. But you can't legislate ethics, and you can't mandate common sense.

For example, foundation systems that work in the beach sand of South Florida won't work in the permafrost of Alaska.

As a frame of reference, the builder we are referring to is not a fly-by-night operator working out of the back of a pickup, but a large corporation. Entrenched bureaucracy can be as damaging as plain incompetence.

Darrell Hay answers readers' questions. Call 206-464-8514 to record your question, or e-mail dhay@seattletimes.com. Sorry, no personal replies. More columns and a message board at www.seattletimes.com/columnists.

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