Helpful? 0

Should sub slab insulation either EPS or XPS be placed above or below the sub slab vapor barrier?

We will be using ICF's with an 8" core, using a capillary break on top of the footing. Sub slab insulation will consist of 2 layers of 2" foam board with offset seams. Sub Slab Vapor Barrier will be Vapor Block 10 type A.

Asked by Jason Macdonald
Posted Sun, 09/16/2012 - 17:21
Edited Sun, 09/16/2012 - 17:21

Tags:

5 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.
1.
Helpful? 0

Polyethylene vapor barrier is always in direct contact with concrete; right in between the concrete and the foam.

Answered by Armando Cobo
Posted Sun, 09/16/2012 - 21:27
Edited Sun, 09/16/2012 - 21:28.

2.
Helpful? 0

If the vapor barrier is between the concrete and the foam, what protects the foam from insects and other degradation? Can an additional layer of poly be placed beneath the insulation for protection? Other ideas?

Answered by Jason Macdonald
Posted Sun, 09/16/2012 - 21:35

3.
Helpful? 0

Jason, Overthinking overdoing...

Underslabs don't need multiple layers with offset seams or taping of seams.

More is not better. The plastic is your vapor barrier for water and radon not insects or whatever degradation. Obtain a proper foundation plan. Here, BSC, your concrete contractor, your architect, your ICF supplier, your GC....

Answered by aj builder, Upstate NY Zone 6a
Posted Mon, 09/17/2012 - 05:01

4.
Answered by Armando Cobo
Posted Mon, 09/17/2012 - 10:59

5.
Helpful? 0

Armando, in my area interior foam is basic foam. Termites avoided by placing foam inside or under.

Curious to costs of products you list and toxicity and climate areas where needed. Thinking the price may be double or more?

Southern homes on slabs impacted by termites to benefit?

Answered by aj builder, Upstate NY Zone 6a
Posted Mon, 09/17/2012 - 13:01
Edited Mon, 09/17/2012 - 13:04.

Other Questions in GBA Pro help

Proper wall to attach rigid foam to the inside of the wall?

In Green building techniques | Asked by Ryan Griffin | Nov 17, 14

Detail for stone veneer

In Green building techniques | Asked by Robert Holland | Nov 16, 14

Does radiant heat recycle water

In Green building techniques | Asked by Celina Jones | Nov 22, 14

Can rigid foam insulation have an air space between it and rim joist?

In General questions | Asked by Susie Derkins | Nov 22, 14

Polyiso on interior

In GBA Pro help | Asked by William Lucrisia | Nov 21, 14
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!