Design Flaws

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APRIL 18 - 24, 2002 -- HELTER SHELTER

Design Flaws

It turns out we Southerners are building our houses all wrong

By Walter Jowers

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 ass-backwards

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 10 List of Dumb Things to Do in the

South. " No. 10 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. 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 a

crop of nasty 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. ly, 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: " OK, so how can I get a nice unvented

attic in my new house? " Well, 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 ass-backwards 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, " he 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 that 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 No. 1 on Joe's list? It's this right here:

" Northerners coming South to design buildings. "

Can I get an amen?

Visit Walter Jowers' Web site at www.housesenseinc.com, or e-mail him at

wjowers@....