We Southerners do have our peculiar ways. Ask folks who aren't from here, and they'll tell you we talk funny, eat greasy, and drive crazy. And they're right.
Well, don't you know, it looks like we're building our houses assbackward besides. So says Joe Lstiburek, an engineer and real-enough Ph.D. at Building Science Corporation (BSC), a Boston-based architecture and consulting firm that specializes in fixing building design problems. My smarty-pants sources say these BSC guys know what they're doing.
Lstiburek has put together Joe's Top Ten List of Dumb Things To Do in the South. Number Ten on the list is our vented attics and crawl spaces. "Venting attics in the South was dreamed up by some disgruntled Yankee pissed about the Civil War and wanting to get even," Lstiburek writes on the BSC Web site (www.buildingscience.com). Joe's thoughts on Southern attics go something like this: The main idea of venting an attic is to flush heat out of the attic during hot weather. Problem is, most of the heat in an attic is radiant heat, which is caused by the sun beating down on the roof. Pulling in hell-hot, humid air from the outside won't do anything to stop the radiant heat, and it won't make the attic significantly cooler.
So, attic ventilation is useless, right? Well, no. It's worse than useless. More often than not, it actually causes bad things to happen. Here's why: We put our air-conditioning ducts in our attics. Unless the A/C installers do a perfect job of sealing the ducts (and they seldom do), the ducts leak. "The moment leaky ductwork is installed in a vented attic," Lstiburek writes, "there is approximately a 25 percent increase in heat transfer to the conditioned space."
Worse yet, there's a fair chance that the moisture-laden summertime air will come in contact with something -- ducts, fittings, the ceiling -- that's cool enough to make water droplets form. In our little home-inspection business, hardly a summer day goes by that we don't see water dripping off A/C refrigerant lines in an attic. Sometimes those drops rust out a furnace. Sometimes they make a puddle big and heavy enough to collapse a ceiling. Sometimes they soak the attic insulation and create a fine environment for mold.
In our part of the world, there's yet another source of humidity in the attic: bathroom vent fans that are ducted right into the attic. We see this in just about every new house we inspect. It's forbidden by the mechanical code, but local builders do it every day, and the local codes inspectors let them slide. Frankly, it's inexcusable, and all of you new-house buyers ought to be raising hell about it.
I know some of y'all are thinking: "Okay, so how can I get a nice unvented attic in my new house?" Well, I say check the BSC Web site. They've got details and pictures and books and consultants ready to take your call. But there's a catch: Even if you know how to build a good unvented attic, most building codes won't let you do it. Codes require attic ventilation. Ironically, the very same codes inspectors who'll let leaky ducts and assbackward bathroom vents slide would nail you if you tried to build an attic without vents.
There's more: The folks who manufacture the asphalt-fiberglass shingles we use down South don't want to guarantee shingles unless the attic is ventilated. Apparently, they think a vented attic will keep the shingles cooler and make them last longer. But it's not high attic temperatures that wear out shingles, it's ultraviolet radiation, according to Lstiburek. Of course, the shingle manufacturers aren't going to drop their attic-ventilation requirements anytime soon. If their shingles fail prematurely, they can usually find something wrong with the attic venting and avoid paying off on the shingle warranty.
Now, about our Southern crawl spaces: The building codes require that they be vented. But Lstiburek says that's a terrible idea. "Crawl spaces are real simple to understand and deal with," Lstiburek writes. "When you vent crawl spaces you bring in hot, humid air and cause moisture and mold problems."
I'm with Joe on this one. Crawl spaces are naturally cool. That's why dogs like to crawl under porches. On a hot, summer day, we home inspectors actually enjoy going into a crawl space. It's just crazy to put vent holes all around a crawl space so hot, humid air can get in. Once that air is in, you've got all the problems you get in attics, except worse. I've seen water condense on ductwork, insulation floor framing, and foundation walls. On a hot, humid day, there's a slow but steady rain in your average Southern crawl space.
When we see mold and fungus growing, it's usually in a crawl space. Combine all that funk with the usual leaky air-conditioning ducts, and you've got all the ingredients for rot, allergies, and illness. As Lstiburek says, vented crawl spaces made sense in the South only in the days when the houses were built on brick piers and there weren't any A/C ducts.
I know you're wondering: What's Number One on Joe's list? It's this right here: "Northerners coming South to design buildings."
Can I get an amen?