Okay,
So I had to dig deeper (to reach bearing soil) than I had planned for my hillside Victoria's Cabin foundation, and it appears that I now will have enough room on the bottom-most part of my stepped foundation for a crawlspace that will be full height (about 8 feel from top of footing to the bottom of a floor joist). I have decided on creating a 30" wide access door, and I will have 4' stem wall below a 4' crib wall. I bought three plastic vents to set into the concrete, but I wonder if I really need them? If needed, can these vents be in the framed part as opposed to the concrete stem wall?
I also read that recent research shows that venting said spaces may not be the best strategy, but this new information is at odds with the codes. Any advice or comment?
Thanks.
Mike
That may be one of those wonderful "it all depends" deals. We've had a couple of threads here about it. Of course I don't remember exactly where.
The Building Science guy, Joseph Lstiburek has written quite a bit about this.
IIRC if you seal the space up, you have to be really sure that there won't be any water getting in there. If there is, and it can't get out you're in trouble, so you might as well have vented the place, and used one of the foam insulations on the underside of the subfloor.
And whether it's reasonable also depends on where in the country you live--or what you are most concerned about (of heat, cold, and humidity) if you live anywhere from, oh, Indianapolis to Jackson, Mississippi.
Since I live in that area, maybe a little east of a straight line between the two, I'm thinking that using that space for a doghouse and/or a root cellar makes sense for me.
Here's the Building Science link--Enjoy (or get more confused):
http://www.buildingscience.com/resources/walls/default.htm
I guess what never made sense to me was putting your plumbing in the crawl space and then putting in vents to insure that it will freeze. :-/
So the debate continues, and I will discuss this with the inspection folks about what they require. If I need to vent it, can I provide the venting via my access door (screened, perhaps) or in the wood framed part of the crawl space? In other words, if vented, does the venting have to be set in the concrete? I wouldn't think it matters, but I am wrong about so, so many things.
Cheers,
Mike
What they will look for is;
#1: adquate sqr. inch's of venting , to sqr. footage of crwal space.
#2: Cross venting flow . (Vents across from each other that promote good flow of air.) No "dead "air spots / corners .
#3: Putting vents in the wood framing is OK , they do not have to be in the concrete.
I have almost the same circumstances as you in my crawl space, including the enough space to have a basement room with an 8 foot ceiling.
I am most definately NOT venting the crawlspace to the outside. Yes, I chose this route because of what I read by Joe Lstiburek (BuildingScience.com) -- AND -- because my crawlspace (yes, the whole crawlspace) will be both air-conditioned and heated.
This will be done by having return vents in each room, that will allow flow from every room to return to the hvac unit via the crawlspace. It's known as a plenum return, is used mostly in commercial hvac applications, and prevents under-pressuring of common spaces when bedroom doors are closed. Of course the ground will be sealed with visqueen to prevent soil gas and radon intrusion. The ground may even be insulated at some point in the future.
Just in case it matters, I am building out in the county (as oppossed to inside city limits), so there are no building inspectors to have to get this approved with.