I’ve seen a lot of nasty crawl spaces. I’ve squirmed through their squalor and squeezed through their narrow confines. Possums, snakes, spiders, and camel crickets have kept me company in the dank, musty underworlds that so many people live above. Moldy joist fur (furry joist mold? joisty mold fur?) doesn’t faze me. (That’s not to say I haven’t had nightmarish experiences.)
Here in the Southeastern US, the standard way to build a crawl space is to vent it to the outdoors. As we all know, though, vented crawl spaces and the psychrometric chart don’t get along so well in a humid climate. Yeah, yeah. I know the psychrometric chart is really like a honey badger and doesn’t care about a stinkin’ crawl space. But you and I both know that in its heart of hearts, the psychrometric chart is really on our side. Right?
I’ve also seen a lot of horrible duct systems. The day I spent going on calls with Moncrief Heating & Air Conditioning recently gave me five more pieces of evidence in the indictment of duct installers. The standard duct system in homes is crap.
The world is NOT flat
Just as Christopher Columbus didn’t sail off the edge of a flat Earth, home builders are now building houses on top of crawl spaces that aren’t vented to the outside. Even better, they’re occasionally putting really nice duct systems in there. Case in point, one of the homes I visited in Nashville, Tennessee last week.
Beautiful! Clean, white plastic to keep the moisture out and make the place seem brighter. A trunk-and-branch duct system that will actually move the air as it should. It has to because this house is getting air flow measurements and commissioning as part of the ENERGY STAR Version 3 certification. Of course, it had its flaws (a bypass duct for zoning, for example), but overall, this system was 8027.2%† better than other duct systems.
Since the crawl space is air-sealed to the outside, the air down there is conditioned from the HVAC system. About halfway down the supply trunkline is this little supply vent blowing conditioned air into the crawl space. It felt wonderful when we entered on that hot, muggy afternoon last week!
My crawl space dream
I haven’t seen numbers on how many new homes are encapsulating crawl spaces like this, but I know it’s a growing trend. In humid climates, vented crawl spaces don’t make sense. In every climate, crappy ducts don’t make sense. It’s nice to see that some home builders are getting that and doing things the right way.
My dream is that conditioned crawl spaces will become the trendy new place to host parties. Some of the best wine I’ve ever had, as a matter of fact, was at a couple of parties in Joe Lstiburek’s crawl space at Building Science Summer Camp. Hey, this could be such a big thing that even architects and interior designers will want to get in on the fun!
† I just made this number up, in case you’re wondering. A lot of the numbers you see in articles on the Interwebs are made up or otherwise meaningless but the authors won’t tell you that. In fact, I read a study that said 81% of all statistics are made up.