36
3214.009
Redmond, Thomas B. and William W. Hotaling, Jr.
The Construction Specifier (Reprint)
Article
The Construction Specifications Institute
1977
July, Vol. 30, No. 7
5 pages
Y
Not too many years ago a builder did a good job when he built a wall with a “U” value of say 0.25, or a total of four resistance units (R-4) thermal insulation. Building codes and officials were not so much interested in this design feature as they were in assuring an adequate fire resistance rating, be it expressed in minutes or in hours. The two resistance ratings were not so much different when you consider each was based on subjecting materials to a heat transfer situation. For thermal energy passage, test conditions were imposed on a steady-state basis. For fire endurance, the test condition was exposure to a “standard” fire. Neither purported to be an attempt at simulating field conditions. Rather, both provided a convenient method for obtaining performance data which could be used in simple calculations for assuring compliance with design criteria. A variety of reasons demand that more sophisticated methodologies be employed today. That was just not so in yesteryear!In the days of cheap and plentiful electricity, oil and natural gas, there was little concern to combat wastefulness. Floor, roof and wall designs could give the least possible insulating value just so long as they provided the “right” fire rating. This was as it should have been, given the economics and the times. A building code was a document stipulating minimum construction practices for securing life safety, if not to conserve property. In effect the building official and code enforcing authority were obliged to ignore inefficiencies of any kind. These restrictions began to disappear in 1973 with the advent of the energy crunch.