Bill Rose on crawlspaces: A bad idea, should be illegalcomments (8) July 22nd, 2011 in Blogs
In seeking subjects for "Inspector" games, I stumbled across a potential gold mine: The U.S. Department of Energy's Building America teams. These folks are constantly working to improve the houses we live in, both new construction and retrofits.
One team, the Partnership for Advanced Residential Retrofit, sent us the photo for the most recent "Inspector" game. The photo comes from Bill Rose, an architecture professor at the University of Illinois at Urbana-Champaign. Bill is a leading expert on building science, especially as it relates to old buildings. His book, Water in Buildings: An Architect's Guide to Moisture and Mold, is one of the best books I have ever read. Honestly.
During the development of the game, Bill and I had an email exchange that boiled down to "Yes, what you want to write is fine, but there is more to the story." Problem is, there is a lot more insight and information in that email than I could use in the "Inspector" game. I asked Bill if I could cut and paste his email into a blog so that I could share it with all of our readers. He thought that was a good idea.
Specifically, we were talking about the crawlspace vent acting as a scupper that would funnel groundwater into the crawlspace. I gave him a couple of options that we could do to fix the problem:
- Seal the crawlspace with pieces of block foundation.
- Add a window well around the crawlspace vent.
Both of us leaned toward sealing the crawlspace, but Bill wanted folks to know that while sealing a crawlspace is better than not sealing it, it is perhaps not much better than a poke in the eye with a sharp stick (my analogy). Crawlspaces, in Bill's opinion, are a bad idea:
"The issue you tackle but which I evaded is the issue of closing crawlspace vents. I evaded the issue not because I don’t approve of closing vents—I do. My reason is a bit more complex than that. Crawlspace foundations were introduced in the '20s and '30s. (There were some interesting older examples, a church in Lamington, N.J., from the 1700s, some industrial examples like the Henry Ford Museum, and of course all the crawlspace partials attached to a full basement.) When they appeared back then, they were always greeted with a caution about moisture problems. I have anecdotal evidence they were never thought of as permanent foundations, and many were excavated to be full basements with a berm—the “Dutch” basement or “Michigan” basement. Seichi Konzo, who started the Small Homes Council here, did the excavation himself on his own house—which, by the weirdest coincidence, Paul Francisco from our shop currently lives in.
That changed right after the war. There is nothing in the record which states that “crawlspaces are suitable foundation types for residential buildings.” Instead, what happened was that some regulatory documents (FHA in 1942, BOCA in 1948) said, “If you have a crawlspace, you must vent.” Note that when this comes from a code body, it strongly implies that, once vented, crawlspaces will be suitable. We have since learned that venting does not deliver suitable crawlspaces, thus the enormous confusion in the minds of the public.
Now we’re saying, “If you have a crawlspace, then you must close vents.” Well, closed vents are better than open vents, no problem there. But the statement itself legitimizes crawlspace construction and implies that the results will be suitable once vents are closed. I don’t buy that. A crawlspace, closed or open, allows a high rate of exchange of soil gas with the house via barometric pumping, and soil gas may contain fungi and bacteria products (myco- and endotoxins), fertilizer volatiles, radon, smells, water vapor, worse stuff with ground contamination. A crawlspace is a settling cavity for dust, dirt, anything, and they are almost never swept clean. A closed crawlspace is indeed “a room in the house”—moreover, it is a very dirty room in the house.
My preference would be a product recall on the crawlspace. OK, won’t happen. So what I am arguing for is opening up to the idea of doing excavation in crawlspaces—to slope to drains or sumps, to create a stand-up space for tornado shelter or for full-height equipment, to remove debris and improve clearance, to improve inspectability, to make it cleanable for once, or to do as Konzo did—turn it into a real basement.
I don’t argue with those who call for closing vents. I’m on board there. I just don’t think that this closes the door on crawlspace issues. So your suggestion about the change is fine, and I go along with it. But I’m cautious about what our recommendation implies."
In an upcoming issue of Fine Homebuilding, rather than covering how to excavate a crawlspace into a basement, we will cover how to seal a crawlspace. (Sorry Bill, it was already on a schedule—call me if you'd like to write The Case Against Crawlspaces). The author of our upcoming article, Jeff Tooley, is the son of another of the nation's foremost building scientists, John Tooley of Advanced Energy in Raleigh, N.C.
posted in: Blogs, green building, water and moisture control, foundations