Crawlspace heat

TimS

If possible, maybe you can use a 8x8 or 6x6 room on the first floor as a utility room for everything. Water main,electric panel, and boiler. I yet to see a crawl space where people go once a week to check things out. I am sure it would be nice crawl space but, a room on the first floor provides a place for service and that occasional quick peek to see if you have a leak etc... I moved my heat system, solar, and manifolds into a 8x8 room and it was the best thing we did to the house. Plenty of room and I can stand up to work and service everything. My 2cents worth.
TimS

Gene Davis_3

A split level house I am designing has two stories atop a slab on grade with stemwall surround, and one story atop a crawl space. See the pic attached for a view of the proposed foundation. I need to add some footing steps and detail, but you can get the idea.

Heat for the living area of 2,028 sf will be via mod-con boiler, doing either all-infloor radiant, or a combination of infloor and panel radiators.

Mechanicals will be in the crawl space, accessible via a short staircase down from the slabfloor lower level of the two story stack adjacent. If necessary, we can deepen the small part of the crawlspace where the boiler, controls, and DHW tank goes.

My question relates to heat required for the crawl space itself, and area of 900 sf. Foundation walls will be R-25 ICF (insulated concrete forms).

With heated space above this crawlspace, what is best practice for heating, or not?

Brad White_203

My only two concerns are

1) Is there any risk of pipes freezing? and

2) Is there a moisture problem whereby condensation could form on the equipment (and in particular any electronics)?

I would calculate the heat loss based on your "knowns" including presumed below-slab temperature. (Forms a radiator if the target indoor temperature is below ground temperature.)

I do not know the specific R value of the ICF's you are using but if the walls are externally insulated, that counts for much. It takes very little to heat such a space.

Once you know the heat loss, I would put in a small panel radiator with a TRV on the "snowflake" setting if you have any doubt. If needed it will open and heat the space if the boiler is operating. If not, you spent a little money.

As a fallback position, a pair of valves ready to go is a good compromise in my experience.

Gordy

My own experience

With my crawl space all though different then yours. 675sf, non insulated block foundation, poured floor, non vented to exterior. Except the louvered 2' x 42" openings to the main basement, and joist bays insulated with r19 foil back.

It gets chilly about 57* when outside temps are single digits. moisture not a problem. The two bedrooms above it are ceiling radiant, and there is a noticable difference in floor temps verses rest of house. Even though the floor is insulated maybe 5* cooler.

You may not be to bad off with ICFs and mechanicals generating some latent heat.

I like Brads suggestions though, it can only help benifit the floor temps above what ever emitter those rooms may have.


Gordy

bruce_21

crawlspace

Thinking about the future of maintenance,etc. if it were mine I'd like to have a rat slab with poly below, a floor drain to exterior daylight screened against critters and lots of lights.

kpc_45

don't worry about....

heat. I have a job out there did 5 years ago. 1200 sq ft Ranch home ICF foundation (Amvick) they put in 1" styrofoan on basement floor... only heat source for the entire basement is a 80K oil fired low mass boiler (NY Thermal- Odessey) The lowest the entire basement got was 62F on design day here in NH... -15F.
Icf boasts a R value of 40... but no air infiltration.
If I ever build I would use nothing else.

Chris S

ICF crawlspace

ICF foundations generally give the rated R value of the combined materials, but they perform like a much higher R value. There are several reasons for this. You cannot compare your installation to a block or concrete foundation.

Basically that space will want to stay around 50 degrees year round because of the earth. Any heat you add to it will more or less remian there, so unless you insulate your pipes really well (fiberglass, not foam insulation), I would think it would maintain closer to 60 degrees without any help. The only thing I would look out for is the humidity level. You may have to vent it. An ICF house we built took 2 years for the basement area to stabilize humidity-wise. Where a concrete or block foundation generally takes several months, sometimes the construction period is enough.
Chris