I am trying to determine the R-values required for a project - a major renovation to a 1940's existing building. The building structure is steel beams and columns, encased in concrete. The exterior load-bearing walls are limestone veneer and brick. There is no cavity in the exterior walls. In the ASHRAE Table for Building Envelope Requirements under walls, above grade , there are several types of elements - mass, metal building, steel-framed and wood-framed. Would this building be considered steel framed or mass? If it's a steel-framed wall, there are two R-values - R-13.0 + R-7.5 c.i. Which value is to be followed? I assume that if the insulation is continuous and not interrupted by metal studs, the the R-7.5 value is applicable.
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Aaron Wascher
Mechanical EngineerAlvine & Associates
13 thumbs up
June 28, 2011 - 2:07 pm
It would be considered a mass wall. Steel-framed is for metal stud based exterior walls.
When you have a steel or wood-framed wall, the two R-values are both required. You need to provide both R-7.5 of continuous insulation as well as R-13 between the studs.
thomas beal
41 thumbs up
July 6, 2011 - 5:14 pm
Just be aware that R-13 insulation is "derated" in metal studs according to the tables in Appendix A. The lower installed R-value takes the metal into consideration. The insulation maintains the full insulation value when installed between wood studs.