NAHB disagrees with the analysis that was used in the development of the R-value requirements, because it compares the cost and savings of each level of increased insulation with the cost, savings and payback of no insulation at all instead of comparing the cost, savings and payback of each level of insulation with that of the next higher increment.
The NAHB Research Center performed extensive computer analyses to determine reasonable incremental paybacks for some of the assemblies in the standard, which NAHB submitted as part of its comments.
Partly because of complexity and questionable economic basis of standard 90.2, no jurisdiction in the United States has adopted it since ASHRAE approved it in 1992.
NAHB has opposed the standard and appealed its original publication to ASHRAE and ANSI, based on procedural and substantive reasons, including:
- The complexity of a 25-line fenestration trade-off equation, which includes inputting the area of glass facing in each compass direction
- A requirement for R-19 wall insulation in virtually all climates
- The use of a “scalar ratio” reflecting a long return-on-investment period in the economic analysis that can be especially unfavorable to first-time home buyers
In the proposed revision of the standard, the fenestration trade-off equation has been eliminated, the wall insulation varied by climate and the economic analysis revamped.
For more information, e-mail Dick Morris or call him at 800-368-5242 x8444.
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