Cold climate slab on grade?

[Alan Gage]

Anybody done one? Any advice or opinions?

Exploring all my options for the build this spring (about 800 sq. ft) and a slab would certainly have its benefits (cost, speed, and no stairs!!) but I'm in northern Iowa and we get quite cold winters. Average January Hi/Low is 23/4. Slabs for home construction just aren't done here, everyone has a basement.

My main concern is how cold will the slab get in winter? I realize no one can directly answer that question but I don't have any experience with a slab that's well insulated along the perimeter and underneath. How much warmer is it than a traditional non-insulated slab?

Today I've been walking around with a IR thermometer pointed at the floor to get a handle on just what temperatures they run and what my socked feet find comfortable. So far the low 60's seem to be the cutoff for comfort on a hard surfaced floor. 59-60 doesn't feel bad with thick carpet.

There is one guy in town I respect who has recently built a couple town houses (I guess that's what you'd call them) on slab and I need to get a hold of him this week to see how he's doing it. I don't believe he's doing in floor radiant heat and one of them isn't finished yet so I could probably get in to take a look. Barefooted and with a IR thermometer of course.

Any input appreciated,

Alan

[bayview]

   My hometown is about 30 miles south of Minneapolis . . .   Because of the high water table, many homes there are built on an insulated slab foundation.   Seems to work well.

  Follow this link and check out figure 21 . . .

http://www.buildingscience.com/documents/profiles/etw-minneapolis-profile/#F21

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[MountainDon]

that's a good link. Insulated slabs do work

[325ABN]

I take it you thinking FPSF? I was considering one untill I decided to go with a walk-out.

[MountainDon]

Yes, although the ones I've seen here are really about the same depth as other 'regular" homes. But the floors inside are much warmer.

Some info download (PDF) HERE.

[Alan Gage]

Great links, some good reading. Glad to hear it's been done up this way by more than a few people with success. I look forward to learning more about it. I'll have to ask the local building supplier, there's only one in town so they know everything that people have been doing.

Bayview - What's your hometown?

Alan

[Alan Gage]

Been doing a lot of research the last few days. Most all of it has been positive, indicating that an insulated slab just isn't that cold in winter. Today I talked to the fella in town that's been building townhouses on slab. He said he's done them both with and without radiant floor heat and both have worked out well for him, no complaints about cold floors (almost all his buyers are elderly). His finish flooring is generally carpet except in the kitchen and bathrooms. He hasn't been doing frost protected shallow footings because he says most of his buyers want to be able to plant and landscape near the foundation so he's been doing the full 4 ft. footings. 2 inches of vertical foam along the outside perimeter and another 2 inches horizontally 4' in from the footings. No insulation under the center of the slab unless he's doing in floor radiant, then insulation under all of it. Houses are heated with forced air (ducts running under slab).

He said he doesn't think the floor seems any colder than the hardwood floors at his house (90 year old home with basement). He said there was a crew doing some work this afternoon so I was welcome to go check it out myself so I headed up there with my IR thermometer and walked around the place barefoot (with socks).

I must say I was very impressed, much better than I expected. It's been very cold here lately. We haven't been above freezing since I don't remember when and the last few nights have been around -10 degrees with daytime highs just above or below zero. Unfortunately the IR thermometer I brought along wasn't the same one I've been using lately and I think it was reading wonky. According to the thermometer the floor was only 55-57 degrees but it felt fine on my socked feet. I know from playing around the past few days that anything under 61 or 62 feels cold on my feet. I checked the wall temps and they were the same as the floor. I looked at the thermostat and it showed the room temp at 65 degrees. The wall right next to the thermostat read 57 with the IR thermometer. I'm figuring the thermotat is correct and that the wall was actually 65 (or close to it) and that since the thermometer said the floor was within 1 degree of the wall that it was around 65 degrees also.

Temperatures aside, like I said, it felt great to my feet. The finish flooring was down with carpet in the main living area and laminate in the kitchen. What impressed me most was that I could barely detect a temp difference (either with feet or thermometer) going from the carpet to laminate.

So I'm leaning pretty heavily towards building on slab. It will be great to take the stairs out of the designs and see what I can come up with.

Alan

[HomeschoolMom]

I thought this was a great video on frost protected shallow foundations:  http://www.youtube.com/watch?v=dKu4T_lgzzg&feature=player_embedded

[bayview]

Bayview - What's your hometown?

Alan

   We had a farm between Farmington and Castle Rock.   But, thats been 35 years ago.

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