0 Helpful?

Is it necessary to tape joints in under-slab insulation?

I'm putting recycled 4" XPS under my slab. Zone 6. Do the joints need to be sealed with anything? I'll put poly on top, under the concrete.

Asked by stephen sheehy
Posted Aug 11, 2014 9:08 PM ET
Edited Aug 18, 2014 5:57 AM ET

Tags:

5 Answers

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

Nope- the taping would have negligible value at best. The amount of thermal bypass air movement under the slab is miniscule, and the poly layer makes it air & water-vapor tight.

Answered by Dana Dorsett
Posted Aug 12, 2014 11:10 AM ET

2.

Thanks, Dana-That's what I hoped was the case. Your explanation makes sense.

Answered by stephen sheehy
Posted Aug 12, 2014 11:19 AM ET

3.

You doing one layer of 4" or 2 layers of 2"? Good to have staggered seams.

Answered by Dan Kolbert
Posted Aug 12, 2014 8:42 PM ET

4.

Dan-we're using 4".

Answered by stephen sheehy
Posted Aug 13, 2014 9:21 AM ET

5.

I used 3" XPS under my basement floor and didn't tape the seams, we did however ensure we taped the seams of the poly vapor barrier extremely well.

Answered by Anthony Hughes
Posted Aug 18, 2014 12:54 PM ET

Other Questions in Energy efficiency and durability

Trying to source 3/4 inch thick coroplast in Maine

In General questions | Asked by kevin freeman | Jun 30, 16

woodshop super-ventilation: Any reason to air seal / insulate?

In General questions | Asked by Kevin Lynagh | Jun 30, 16

Direct vent vs. power vent gas water heaters

In Mechanicals | Asked by Erik Addy | Mar 8, 16

How to work with a very deep truss in vaulted ceiling.

In Energy efficiency and durability | Asked by Barry Reicker | Jun 29, 16

Does anyone have experience with Zehnder ComfoFlex?

In Mechanicals | Asked by Trevor Fontaine | Feb 9, 16
Register for a free account and join the conversation


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