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Community and Q&A

Thermal break?

GBA Editor | Posted in Energy Efficiency and Durability on

Remodeling a bathroom in Michigan — 3’x5′ shower, two walls of shower are exterior walls, wall composition is vinyl siding, 1/2″ foam board insulation, 1/2″ sheathing, 2×4 studs w/ 3-1/2″ batt insulation. New cement board and new tile to be put on walls and drypack pan with stone shower floor. What can be done to provide a thermal break so that in the winter the walls and floor will not be ice cold? Thanks.

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  1. GBA Editor
    Martin Holladay | | #1

    If you've only got 3 1/2 inches, the answer is clear: closed-cell spray polyurethane foam.

  2. Doug McEvers | | #2

    You could also surround the exterior shower walls and floor with styrofoam, I use foam under tubs and shower units with a thin mortar base for strength.

  3. Robert Riversong | | #3

    Combine answers #1 and #2 and you've got what you're looking for.

    The spray foam will maximize the R-value of the stud cavities but not create a thermal break. The XPS foam board on the floor and walls will add R-value and offer a thermal break over the framing as well as reduce the air and vapor permeability of the assembly.

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