flash and batt

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Insulating a New House

An owner-builder looks for advice on the best way to insulate exterior walls in a new build in Ontario

Posted on Aug 21 2017 by Scott Gibson

An owner-builder planning a new home in southern Ontario isn't looking for a net-zero house, just one that's well insulated and protected from moisture problems. The question is whether his proposed wall system is his best option.

"I'm unwilling to put foam board on the outside and vapor barrier on the inside," writes User 6782048, whom we'll just call Ontario, in a question posted on our Q&A page. "Just seems wrong."


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Image Credits:

  1. Dunktanktechnician / CC BY 2.0 / Flickr

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Flash-and-Batt Insulation

Spray foam between the studs can reduce air leaks, but a continuous layer of exterior rigid foam makes more sense than flash-and-batt

Posted on Sep 11 2015 by Martin Holladay
prime

Closed-cell spray polyurethane foam insulation has several desirable characteristics. It’s an excellent air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both., an excellent vapor retarder, and it has a high insulating value per inch (about R-6). Unfortunately, it’s also expensive.


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Image Credits:

  1. Image #1: Pacific Northwest National Laboratory
  2. Image #2: Martin Holladay
  3. Image #3: Fine Homebuilding

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Flash and Batt in the Roof

Adding up the R-values of different types of insulation may not yield a sum that the building code will accept

Posted on Feb 24 2014 by Scott Gibson

"Flash and batt" is an insulation technique that combines the air-sealing superiority of spray foam insulation with the cost benefits of fiberglass batts. An inch or two of polyurethane foam seals the cavity and the batt insulationInsulation, usually of fiberglass or mineral wool and often faced with paper, typically installed between studs in walls and between joists in ceiling cavities. Correct installation is crucial to performance. adds R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. without costing an arm and a leg.

That's roughly the plan Dave Frank is considering for the roof of a house — presumably his own house — in Climate Zone 5. But his plan contains a twist: He wants to spray the underside of the roof deck with foam and install the batts between the joists at ceiling level.


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Image Credits:

  1. Karen Doherty/National Renewable Energy Laboratory

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The Flash-and-Batt Method

This oddly illicit-sounding insulation system is becoming more common

Posted on Jan 22 2013 by Erik North

One thing I’ve noticed over the years is that construction methods don't change quickly — and when they do change, the change is apt to be along the lines of current practices. That makes sense. It’d be near impossible to run a business if you were changing your technique and product five times a week.

Flash and batt insulationInsulation, usually of fiberglass or mineral wool and often faced with paper, typically installed between studs in walls and between joists in ceiling cavities. Correct installation is crucial to performance. is one example of a new technique being implemented by insulation contractors. Flash and batt is a hybrid insulation approach combining fiberglass insulation and closed-cell spray foam.


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Image Credits:

  1. Fine Homebuilding

Why Flash and Batt Makes Sense

Posted on Sep 22 by Martin Holladay

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Closed-cell spray foam and fiberglass batts can be used together to maximize performance and minimize cost

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