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Veteran Contributor

Re: shop insulation


@fernwood wrote:

On the steel building we just put up we purchased the insulation with the building package.  Put 4 inch bat in the roof and 3 inch on the sides.  Came in precut rolls about 6 ft wide.   Was not that bad to put on after we figured out the best way to do it.  Just put a roll on and put the metal over it. 


Don't remember the R value or price but seems like it was around $2K.  Will look up the price for you if you need it.   

We have a builder at home that puts the ceiling steel up before he puts the roof steel. He then insulates the ceiling and puts the roof steel on as the insulation goes on. That way the insulation is not pinched between the roof steel and purlins. I've always thought it nuts to put 3 or 6 inches on the roof and then pinch it down to nothing with the screws into the purlins.


If yhe purlins are 8in you can have a full 8in of insulaion across the whole roof. A

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Jim Meade / Iowa City
Senior Advisor

Re: shop insulation

Most government and industry sources online say closed cell petroleum based insulation has about R9 per inch which drifts down to about R7 over time.  2" would be R14, if this is correct.


Here's a good article from Purdue, but it's long.


Here's a quote from NDSU:  
"The minimum recommended insulation level for a heated shop is an R-value of 15 to 20 in the walls, 25 to 30 in the ceiling and 10 for the doors. It is also recommended to insulate the foundation with at least 2 inches of polystyrene insulation (R-10 to 12) to a 24 inch depth. This helps keep the floor warm, reduces heat loss and eliminates frost buildup on the inside perimeter concrete."


the source for the above.


This is from Canada on foam insulation.


From about 15 minutes of surfing online trying to stick to government and industry sources, it appears to me that the R-value of spray on foam is from R9 to R6.  It's hard to believe the claims the insulation salesman made.

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JJ Johnson

Re: shop insulation

Closed cell foam has a R value of 7-9 per inch of thickeness. It acts like 24 per inch since it  seals completely, and you don't have to use a vapor barrier. I am spraying my walls 1" thick and covering it with 6" of batt insulation. I am planning to blow insulation in above the ceiling later.

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Re: shop insulation

Get as much in the ceiling as you can.  That's where the vast majority of heat loss is.

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