How can a finished roof with steel trusses be modelled in BEopt?

asked 2019-12-14 13:32:04 -0600

updated 2019-12-31 14:18:48 -0600

I didn't see any choices for steel framed trusses in the finished roof category. I don't see any obvious options. The wall insulation does have steel stud choices however. Thanks.

answered 2019-12-16 09:53:06 -0600

shorowit

11801 ●200 ●9 https://www.nrel.gov/b...

BEopt cannot explicitly model steel trusses. You will have to choose a wood truss option with an equivalent assembly R-value.

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Thanks. I researched steel truss assembly R-values compared to wood and the best I could find was https://www.sbcmag.info/article/2012/.... Because the deltas in the table aren't consistent I chose an average R-7 difference between steel and wood and increased an existing wood asssembly's framing factor in the 'Finished Roof' options to be R-7 less. I'm not sure if the top chord depth matters so long as the framing factor is adjusted to reduce the assembly R-value. Does this sound reasonable? Any other sources for comparing steel trusses to wood?