[Greenbuilding] Crawlspace

[Stuart Fix]

>To me, the conditioned crawl space seems a bit like turning the crawl
space from
>a semi outdoor environment into something more like an unheated basement.
So,
>if basements work in the climate in question maybe a conditioned crawl
space
>would also work?
>In a way, the conditioned crawl space seems better than most basements in
that
>the walls are insulated, so the crawl space temperature would be warmer
and RH
>lower?

>The conditioned crawl space idea has been out there for some time -- I'd
guess
>that there should be a lot of data out there on how it has worked out for
people
>and what kind of climates it works in.

>Gary



Play nice, boys.

Something I should have mentioned. I deal with high performance building
design, and therefore what I've advocating is a best practice scenario.
There are obviously many non-ideal buildings existing out there, and the
particular solution to remedy each scenario will be unique.

In general, however, I'd recommend two approaches which can deliver
durable, energy efficient performance:

1) Unheated crawlspace
	- treat the crawlspace ceiling/home floor as an exterior envelope
assembly. Make it air tight, well insulated, and with a vapor retarder on
the warm side.
	- then treat the crawlspace as the outdoors. Ventilate that space
sufficiently to keep it dry on an annual basis, the amount being climate
dependent. Hot humid climates should not have enclosed crawlspaces. Poly
on the ground underneath will help, if site grading keeps it dry.

2) Heated crawlspace
	- this is not a crawlspace, it's now a 'storage' space inside your
home, treat it as such. It should be dry, clean, & accessible.
	- the home's thermal envelope, being air tight, well insulated, &
with vapor retarder on the warm side, should totally enclose this space.
	- RE Gary's question above, yes. But instead think of it as a
short basement, or a new slab on grade floor, not a crawlspace. If you
just heat a typical crawlspace, you'll waste a lot of energy.

If you have a home with some mixed combination of the above, and are
having issues with excessive energy usage, moisture/rot, then I suggest
you strive towards one of these options.

Cheers,

Stuart Fix, P.Eng., LEED® AP
PHI Certified Passive House Designer
MASc. Building Science
Mechanical Engineer
ReNü Building Science Inc.

52 Airport Road | Edmonton, Alberta | T5G 0W7| C. 780.554.8192
| sfix at renubuildings.com