Polystyrene Foam Insulation in Long-Term Building Applications – Effective R-values
Page 10
5.3
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5
4.4
4.3
4.2
Years
Figure 5. Es mated R-value over Time for a U.S. 1 inch Type X, IV XPS
16-20
0.95
0.93
0.91
0.89
0.87
0.85
0.83
0.81
0.79
0.77
0.75
0 5 10 15 20 25 30 35 40 45 50
R-value
(°F•ft
2
•h/BTU)
RSI
(°C•m
2
/W)
Material Initial R-value 5-year R-value
1
50-year R-value
2
XPS Type X 5.0 4.67 4.3
XPS Type IV 5.0 4.79 4.3
EPS Type II 4.0 4.0 4.0
EPS Type IX 4.2 4.2 4.2
1
Estimated based on CAN/ULC-S701.1 Types since ASTM Types are similar to CAN/ULC-S701.1 Types
2
Estimated based on available research
16-20
The R-values of insulations that contain blowing agents decrease over time. As shown in Figure 5, the R-value of XPS
continually decreases over 50 years. The R-values of insulations that contain only air do not decrease over time. The
R-value of EPS products is constant over 50 years.
Table 3. R-values over Time for XPS and EPS
Material EPS EPS XPS XPS
ASTM C578 Type II IX X IV
F
AGE
1.0 1.0 0.86 0.86
Table 4. F
AGE
for EPS Type II, IX and XPS Types IV, X at 50 years
The information contained in Table 3 allows for the determination of the aging adjustment factor for EPS and XPS.
