Effective Insulation R-Values in Steel vs. Wood Framing Types

Green Building

Effective Insulation R-Values in Steel vs. Wood Framing Types

Also published on May 29, 2017 by BNP Media through the Building Enclosure Blog.

The value of continuous insulation is a source of contention among some building design and construction professionals. Increasingly stringent energy code requirements are calling for minimal amounts of continuous insulation that some claim are prohibitively expensive, structurally complicated, or marginally impactful versus increased cavity insulation.

Professionals are generally aware of the potential for thermal bridging in construction assemblies – the phenomenon by which heat conducts more readily through structural/support members relative to the adjacent cavity insulation, thus reducing the effective performance of the overall thermal barrier. Yet, few professionals understand the effective impact structural framing has on the rated R-value of a cavity insulation product.

Seeing impressions of studs in a wall system during an infrared scan is one thing, but how much of a difference does thermal bridging actually make?

…Well, if your assembly utilizes steel studs, the answer is: A LOT.

The following table presents the effective insulation/framing layer R-values for both steel and wood stud wall framing.

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2 thoughts on “Effective Insulation R-Values in Steel vs. Wood Framing Types

  1. Is that really “true”? (IE)
    Assuming insulation at approximately R-7 per inch (Foam)
    – Wood R value is about R-1 per inch of depth. So the area of thermal break area is 1-1/2″ wide (Times every where a stud is used in the wall) x 5.5 inches deep.
    — Wood – Area of Thermal Gap @(R-5) – 1.5 wide x 5.5 depth)
    -Steel stud thermal break is ? (0) about 1/8″ wide (times each place a stud is used) with about R-38 filled inside stud cavity.
    — Steel area of thermal gap @(R-0 for first 1/8 inch, R-38 for remaining 5.375″)
    Question does Steel get a worse rap then it deserve because people calculate the true R-Value unfairly?

    1. Thank you for the comments, Matthew. These figures visualize values approved by the technical committee who developed the cited edition of ASHRAE Standard 90.1 You will want to consult that standard for the methodology applied to arrive at these figures.

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