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Crawlspace insulation in Utah (Rocky Mountain Region)?

hoppy1214's Avatar

Join Date: Jan 2017
Posts: 1

01-15-17, 11:17 AM   #1  
Crawlspace insulation in Utah (Rocky Mountain Region)?


I live in Salt Lake City, Utah and am having a hard time finding information about crawlspace insulation for my region.

What is the proper way of dealing with an existing crawlspace in a dry climate like Utah? Should I permanently close off the vents, insulate the walls, and add a vapor barrier to the floor? Or should vents be left open and insulate the floors? Something else?

I live in a single-story townhouse built in the 1950s. The current crawlspace currently has open foundation vents. It is block wall and no type of insulation currently. There is some plumbing in the crawlspace but nothing else.

Thank you in advance for any help.

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Bud9051's Avatar

Join Date: Oct 2008
Posts: 9,772

01-15-17, 12:06 PM   #2  
Hi hoppy and welcome to the forum.
I checked the climate map and you do get some cold weather:
Both of the options you listed are possible. My preference in a cold climate is to insulate the crawlspace walls, cover the ground floor, and add in some heat to condition the space. This way that heat warms the floors. If you insulate the floors and ventilate the crawlspace then the only way heat gets to the floors is from the space above, and convection tends to move that heat up not down.

You would want to be sure the house to foundation and perimeter rim is very well air sealed.

Rigid insulation against the foundation walls may need to be covered, check local requirements. An easy solution would be Dow Thermax as it comes with a tested foil facing that can often be left exposed. I say often as local codes can be more restrictive.


stickshift's Avatar
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Join Date: Oct 2004
Posts: 18,476

01-16-17, 10:18 AM   #3  
My 2 is there are two ways to deal with a crawlspace:
1. Open it to the outside and seal it from the house. In this case, you insulate the ceiling.
2. Open it to the house air and seal it from the outside. In this case, you insulate the walls.

Either way, you put a vapor barrier on the ground. Option 1 is more common in warm climates, option 2 more common in cold. Given that you have plumbing in the space, I can only recommend option 2.

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