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What is Long Term Thermal Resistance (LTTR)? Click here to find out.

Long-Term Thermal Resistance (LTTR)*
TAPERED ACFOAM® II & TAPERED ACFOAM® III
MARKING
THICKNESS
SLOPE PER
AVERAGE
 
in
mm
foot
30.5 cm 
LTTR Value
RSI
AA
0.5"-1.0"
12-25
1/8"
3 mm 
4.5
.79
A
1.0"-1.5"
25-38
1/8"
3 mm
7.5
1.32
B
1.5"-2.0"
38-50
1/8"
3 mm
10.6
1.86
C
2.0"-2.5"
50-63
1/8"
3 mm
13.7
2.4
X
0.5"-1.5"
12-38
1/4"
6 mm
6
1.06
Y
1.5"-2.5"
38-63
1/4"
6 mm
12.1
2.13
G
1.0"-2.0"
25-50
1/4"
6 mm
9
1.58
H
2.0"-3.0"
50-76
1/4"
6 mm
15.3
2.69
JJ
0.5"-1.25"
12-32
3/16"
5 mm
5.3
.93
KK
1.25"-2.0"
32-50
3/16"
5 mm
9.8
1.72
Q
0.5"-2.5"
12-63
1/2"
12 mm
9
1.58

* Long-term thermal resistance values of the foam were determined in accordance with CAN/ULC-S770. All test samples were third-party selected and tested by an accredited materials testing laboratory.  The R-value for .5 in. perlite (1.39) was provided by ASHRAE Handbook, Fundamentals.  The R-value for .25 in. glass-mat gypsum board (.28 R-vaule) was provided by the glass-mat gypsum manufacturer.
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