Issue link: http://cp.revolio.com/i/1121626
Polystyrene Foam Insulation in Long-Term Building Applications – Effective R-values Page 5 Impact of Aging The FTC's R-value Rule requires that the published R-value of insulation fully reflects the impact of aging on the insulation. The process of aging causes some insulation to lose its captive blowing agents over time. XPS uses gaseous blowing agents, which initially contribute to better R-values, but over time dissipate causing the R-value of XPS to decrease. In contrast, EPS contains only air, so its R-values do not decrease over time. In Canada, XPS manufacturers are required to publish long-term thermal resistance (LTTR), which is an estimate of the product's R-value at five years of age. The LTTR requirement is distinct from the insulation's initial R-value or an R-value determined by a short-term conditioning method. Nonetheless, LTTR does not reflect the full extent of aging over the life of the insulation when used in buildings that are anticipated to have a minimum lifetime of 50 years. Figure 1 shows the R-value for EPS Types II, IX and XPS Types IV, X over time. 0 5 10 15 20 25 30 35 40 45 50 5.5 5 4.5 4 3.5 3 Age, Years R-value (°F•ft 2 •h/BTU) EPS Type II EPS Type IX XPS Type X XPS Type IV Figure 1. R-value Over Time for EPS and XPS RSI (°C•m 2 /W) 1.00 0.90 0.80 0.70 0.60 0.50 XPS Initial R-value XPS LTTR R-value