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Hard Time Calculating R Value of Brick Wall

Another DIYer here. I am converting a 120 year old 2 flat in Chicago to a Single Family Home.

I am having trouble coming up with a heat loss number for my primary living area. The space is pretty big - approximately 31 x 20 (620 sq ft) with 10 ft ceilings. It is 4' above grade with a heated basement below and a second floor above.

I put all of the design elements into RadiantWorks and get a heat loss value between 19 and 26 btu/ft/hr. The difference mostly depends on the R value I assign to the exterior walls.

Here is what I have:

~14" Chicago Common Brick wall (3 bricks wide).

2x4 framing, laid flat

1.5 inch batt insulation (I can pay more and get Tuff-r board)


My current thinking is I probably have an R value of 3-5 on the low end and 10-12 on the high end.

Any thoughts / wisdom greatly appreciated!



  • Gordy
    Gordy Member Posts: 9,546
    Wall R Value

    Common Brick .80x3=2.4

    1.5" Fiberglass inulation 3.14 per inch x 1.5"=4.71

    1/2" Drywall .45

    Outside air film = .17

    Inside Air film= .68

    Total R value  = 8.41

    A little more could be added for the mortar between the rows of brick.

  • Bob Harper
    Bob Harper Member Posts: 1,026
    moisture content makes a difference

    The industry figures for the R value of common brick are based upon dry bricks-not wet. In reality, bricks are a moisture storage system that CONDUCTS heat until dried out. That is why it is so important to have a proper drainage plane behind brick veneer and why masonry chimneys are such heat sinks---they don't have drainage planes.
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