|From: Therese Stovall <firstname.lastname@example.org>
Date: Mon, Nov 15, 1999 2:41 PM
Subject: ANPR Comment, R-value Rule, 16 CFR Part 460
Comment about the aging of certain types of cellular plastics insulations which experience a change in their thermal conductivity due to gas diffusion through the cell walls:
ASTM Test Standard C 1303-95 provides clear guidance to determine the lifetime R-value of a homogenous, unfaced foam specimen. This test method has been accepted as an industry consensus standard and has been subjected to multiple round-robin tests that confirm its accuracy and repeatability.
Alternative ŠacceleratedĂ aging methods that rely on elevated temperatures do not provide adequate information to predict the foamĂs aging under normal use. There is no way to correlate the results of the elevated temperature test to the in-use performance of the product because there is no direct correlation between the plastic cell wall diffusivity at elevated temperatures to that at normal use temperatures. The other method suggested, aging a product for 180 days, ignores the long-term aging that continues to occur beyond this time frame for all but the thinnest foam boards. For these reasons, the phrase "or another reliable procedure" should be deleted because of its lack of specificity. Note that during the aging process, a foam can loose a significant fraction, on the order of 30%, of its insulating value.
At this time, a satisfactory aging method for these boardstock insulations with impermeable facers (e.g., aluminum) has still not been developed. Tests to date have shown that some specimens undergo negligible aging effects, while other impermeably faced products age at the same rate as unfaced products. Therefore, the Rule should state this fact and require "direct" aging of products with impermeable facers (i.e., aging over time of samples as they are produced at full thickness and with facers attached.
Comment regarding the need to start educating consumers about R-values in SI units: As the loss of the Mars probe tragically demonstrated, our nation has a way to go in making the logical transition from English to SI units. Many consumer products have helped with the transition by providing SI units in parentheses for a long period of time. This dual-label time is necessary to educate and accustom consumers to the new label units. It is time to start this process with insulation products. An R-value in SI units is equal to the English R-value (which represents h-ft2-F/ Btu) divided by 5.678 to give m2-K/ W. For example, I suggest that a product be labeled "R30 (RSI-5.3)". Note new area code for phone numbers!
Therese K. Stovall
Oak Ridge National Lab