Question

I'm trying to decide between flash and fill (BIB) and all open cell foam for exterior walls.

Asked by sunil
Crownsville, MD

Hi, I live in MD in climate zone 4 below Baltimore, but almost 5. We are building a house with 2x6 walls 16" OC all brick exterior. I have an estimate for 1 inch closed cell then blown in fiberglass fill and a quote for all open cell foam. The all open cell is 30% more, should I be worried about condensation in walls and go with the all open cell foam or will I be safe in this climate zone with the flash and fill. My neighbor did the flash and fill however only on 1 wall not all without any issues. I need to decide soon and am confused on which way to go. 

Answer

Sunil,

If you wish to proceed with the Flash and fill technique you will need to install 2" of closed cell foam to achieve the proper vapor barrier.

This additional 1 inch of closed cell foam will increase the cost.

I would recommend that the installer requote the project meeting the manufacturers specification for an effective vapor barrier prior to making your decision.

Best of luck,

Harold Remlinger, AIA LEED AP, NCARB DesignTeam Plus, LLC

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