# Insulating my concrete block walls in workshop



## Windows on Wash (Aug 30, 2011)

That should work just fine. That is probably the easiest way to do it.


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## Gary in WA (Mar 11, 2009)

Where in Michigan are you? 2" foam may not be enough... XPS or EPS, faced or unfaced?
Closest city?

Gary


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## pointer80 (Feb 2, 2012)

I live in northern Michigan about a hour north of Grand Rapids. I plan on using 2 inch xps on the walls. I have 10 ft. high sidewalls and 6 inch insulation in front wall and ceiling(the front wall is 2x6 construction and the 2 side walls and back wall are concrete block). Originally this structure was built to be a "inground house" with a walk out front but the people sold the property to us and I built a house with a attached garage and turned this structure into my workshop garage. I heat with a outdoor wood boiler and have a hanging heat unit in my workshop. You definately can notice when the heat is on even without any insulation on the sidewalls, but that is about it. I want it comfortable in there to be able to work but I do not plan on keeping it super hot either. If I could be out there in a sweatshirt in the coldest months I would be happy. Any ideas would be appreciated. Thank you


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## Windows on Wash (Aug 30, 2011)

Given that is is a workspace and your won't be heating it to 72 or that much, 2" of XPS should be good.


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## Gary in WA (Mar 11, 2009)

Depends on how thick a sweater you want to wear.... Minimum Energy Code for a house with *mass walls* (above-grade) in your location requires R-17 (footnote "i"); http://energycode.pnl.gov/EnergyCodeReqs/index.jsp?state=Michigan

If you heat it to* 68* F*, using the 3 coldest months average temperatures, no condensation on the CMU's at above-grade wall elevation= *23%* Relative Humidity. 

4' below grade would rate +5* warmer wall, safe with interior RH at 44%.
8' below-grade = +10* warmer with 52% RH.

Change it to* 60** indoor temp= only* 21% RH *at above-grade portionswith block/insulation face temp at *30*F.

*4' down *= *29% RH 8' down = 35% RH

So it depends on: the elevation of wall in the earth warming soil, the thickness of the foam (2" is below code even for your area, cross the county line into Newaygo - R-19 required in basement), the outside ambient air temps and the temperature you set for comfort. I used 25*F for the math, anything lower will give lower yet RH. Be sure to clean the CMU's of dirt/organic matter that could mold before you glue the foam board. Use 1' square (roughly) grid pattern to limit workshop air/moisture from compromising it all, ADA the drywall; http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/

Gary


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## Windows on Wash (Aug 30, 2011)

Well… If you want to get all factual about it.

Gary, as usual, has provided you with all the technical information that you could hope for to make an informed decision.

He's usually 99% right about these things and he his certainly correct that you only get one chance to insulate this thing properly depending on your intended use.

If you wind up using a supplemental heating source for the workspace that introduces additional humidity, i.e. combustion type heating sources, you run the risk of having condensation issues at the wall.

XPS is a generally very vapor movement prohibitive insulation and, if the insulation is well attached, sealed at the seams, and sealed to the block, there shouldn't be much moisture even making it to the block wall.

If you're worried about wall depth or don't want to mess with framing, add another inch to be sure and call it a day.


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## Gary in WA (Mar 11, 2009)

The more information one gets, the better choice of product for the application, IMHO. 
With EPS Type 1-9; XPS- unfaced, foil-faced, poly-faced; and Polyiso, with R values ranging from R-7.4 to 14 for 2" product. Add in no idea where he was at, hard for me to tell him it sounds good.

Gary


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## pointer80 (Feb 2, 2012)

Thanks for the info guys, very helpful. After I did some pricing and checking I actually think my best bet is going to be to run 1/2 inch foam on the walls as a moister barrier and then stud the walls and run fiberglass insulation in the cavities. I was surprised that the price is almost the same. I believe the installation will be just as easy because there will be no drilling a bunch of holes in the concrete block and screwing a zillion tapcons. Also I will be getting about R-17 instead of R-10. What do you guys think? Thanks.


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