Insulating before the pour - advice sought

[NuthinFancy]

About to start building a detached 20 x 30 workshop on a poured slab and thinking about insulating the concrete as I intend to heat/cool the building with a mini-split type unit. No in-floor heating here.
Naturally, the walls and ceiling will be well insulated.

After some research, my initial thought is to go with 2" XPS (plus 6 mil plastic) under the slab and on the outside of the perimeter, which will have a 9" curb wall, mostly above grade.

First question that came to mind is: how do you protect the XPS that's above grade on the perimeter?

The ground around the building will be either stone or wood mulch, so no grass cutting or trimming to worry about, but paint alone seems inadequate as well as high-maintenance.

Suggestions?

 

[Bondo]

First question that came to mind is: how do you protect the XPS that's above grade on the perimeter?

Ayuh,..... Put the foam board, Below grade,.....

 

[bannerd]

Ayuh,..... Put the foam board, Below grade,.....

What he said ^

 

[gnpenning]

Are you going to insulate both the outside and inside of the wall? If you are the inside can stop at the height of the slab. The outside you can run metal or siding to just above ground height. Or you can put a mesh on it and use plaster or stucco type product.

As you know insulating under the slab and having a cold joint between the wall and slab is a waste of insulation under the slab. Concrete does a great job of transmitting heat and cold. If you left the above grade foundation uninsulated you would be wasting the insulation in your walls. It's always best to stop from coming in, instead of trying to control it after.

You can put on a thicker base plate sticking out the same thickness of the foam board to keep a vertical plane. Make sure you have a thermo break at all door openings including garage doors.

I would suggest using ICF for your foundation. It will insulate the foundation and you won't have to strip forms after. Plus the are very easy for the DYI'rs to install. If your foundation wall is short you can form and pour with your footing and do both in one pour.

 

[kwschumm]

While researching this, in relation to radiant floor heat, the research seems to indicate that 70-80% of the heat is lost between the slab and footings so that is the place to insulate in a maximum bang-for-buck scenario. It's, of course, even better to insulate under the slab, too, but if you want to economize the perimeter insulation is more important.

 

[theoldwizard1]

First question that came to mind is: how do you protect the XPS that's above grade on the perimeter?

Assuming you are going to have a perimeter footer/foundation/rat wall that is a separate pour, after you strip the forms you can install it on the inside.

If you plan on installing it vertically on the outside of the foundation, they make something like a thin concrete that can be applied.

 

[TLCObsession]

On the inside you taper the vertical foam on the inside of the stem wall so it is 3/8" thick at the poured surface of the slab. I have seen some guys use it full thickness and use an 8# sill plate covering the foam with a 2x6 framed wall on it. By the time you add sheetrock and a base molding you can make it disappear.

Outside, you can protect the foam at, below or above grade with Hardiplank.

 

[homebuilt burner]

I used Tuff II a stucco like product at Menards. Looks like concrete and accepts paint. Not expensive and easy to apply.

 

[atch]

On a house I built some years ago I put 2" of Styrofoam on the outside of the basement walls; all the way from the bottom to the top of the concrete walls. There was about a foot of concrete above outside ground level. I had gutters made that matched the siding color. You know; the stuff that they make on-site that starts out as 24" (+/-) wide aluminum on a roll. I had them leave enough of the flat aluminum to cover the top 2' of Styrofoam all the way around the house. Then we backfilled and the dirt covered about a foot of aluminum and about a foot was exposed above ground. The bottom row of siding then covered the top few inches of the aluminum. Worked great. We lived there for 13 years and the basement walls were NEVER cold and there was never any musty odor in the basement.

So, in conclusion, if you're going to have gutters maybe you could cover the foam with the same material.

I don't recall how much it cost to do this but it wasn't very much. b-t-w; don't quote me on the 24" width.

 

[Bondo]

Ayuh,.... I think I miss read the question,....

I was thinkin' of a Frost Curtain, comin' out from the foundation, rather than the vertical surface of the foundation,...

 

[K'ledgeBldr]

You didn't say specifically, but I'll assume you're referring to a "mono-slab".

This should answer most of your questions-
http://web.ornl.gov/sci/roofs+walls/insulation/fact sheets/slab insulation technology.pdf

Actual procedures can vary if you're doing a separate footing/foundation and slab.

Here's some other info-
http://buildingscience.com/documents/insights/bsi-059-slab-happy

 

[homebuilt burner]

atch's idea works as well. We did this on my parents house 10 years ago.

 

[vision8]

I found door cut-outs from a manufacturing door company these were from outside mandoors that did the job; they are scrap to them and have to pay for disposal fees to get rid of these. Also, found used flat roof insulation with some tar on them to use under my pour. I did not have time to install the boiler for radiant heat yet ( only did loops on the perimeter of the slab but for the extra few $ the pex is in the slab ) but did use the cutouts on the outside and the inside of the foundation.

 

[Toolfool]

I insulated the outside of my foundation with 2" XPS and had galvanized metal bent to cover. 6" up the wall, 2" over top of foam board, 20" down into the ground before backfill. And four outside corners.

 

[Elginz]

I insulated the outside of my foundation with 2" XPS and had galvanized metal bent to cover. 6" up the wall, 2" over top of foam board, 20" down into the ground before backfill. And four outside corners.

Something like this. I used 3/4 inch on the outside and covered the edge with the sill plate, and the face with tin up a few inches and below grade a few inches. I also a went out from the footing two feet (should be 4 feet).

 

[NuthinFancy]

Thanks for responding, ToolFool. The pics are helpful - I really like your approach.
How did you detail the corners? Overlap the ends or something else?

Nice shop, btw.

 

[Randy in Maine]

I would still install the 1/2" pex tubing 12" on center so that the next owner of the property will consider that a big asset.

 

[Toolfool]

Thanks for responding, ToolFool. The pics are helpful - I really like your approach.
How did you detail the corners? Overlap the ends or something else?

Nice shop, btw.

Had my HVAC shop bend and solder outside corners. Sides overlap the corners.
And thanks for the compliment.