Fluid applied vapor barrier for crawlspace foundation walls?
JeffS1
| Posted in Energy, Heating & Insulation on
I see very little about using a fluid applied vapor barrier on the crawlspace side of foundation walls as an alternative to sheet vapor barriers. A sheet vapor barrier would of course be used on the ground and up the walls six inches. But if a fluid applied could be used on the rest of the foundation walls to the top, it would be a big labor savings for my situation. Is it a long-term adhesion issue? I just don’t find much discussion of this alternative online. Thank you.
Replies
I imagine there could be some adhesions concerns if the foundation wall was changing in hydration status. Also, where is the thermal envelope? Is the exterior wall insulated or is it the crawlspaxe ceiling/1st level floor the air and thermal barrier?
The exterior foundation wall is not insulated. I'm creating a conditioned (encapsulated) crawlspace so there would also be no insulation in the 1st floor, only at the foundation walls and rim joist area.
How are you attaching the insulation to the interior foundation walls? You’ll want to make sure the materials all are compatible. I’m doing mine now. Did 4” of rigid foam (two 2” layers) and then will be doing the tack tape on the foam. The free flap on the 15 mil vapor barrier I’ll be caulking closed right above the tape too just as some added benefit and adhesion.
I believe I'll attach the foam board insulation with plastic anchors. I wish I had one of the powder actuated insulation nailers but they're pretty expensive and this is a one-time job. The butyl strip idea is just so when the anchor pierces the VB (whether poly or liquid) it self-seals around the anchor. Not perfect, but pretty good.
The fluid applied vapor barrier may not meet flammability requirements for the walls.
Good point, thank you.