Table 15 – Maximum Allowable Exposed Vent Lengths in Unconditioned Space Insulation Table - - Ft. / M
Unit Size
Uninsulated
Pipe Dia.
1 ½
2
in.
20
20
20
Winter
0
10
5
Design
-20
5
Temp
°F
-40
Unit Size
Pipe Dia.
1 ½
in.
20
15
Winter
0
15
Design
-20
15
Temp
°F
-40
10
Unit Size
Pipe Dia.
2
in.
20
20
Winter
0
20
Design
-20
15
Temp
°F
-40
10
Unit Size
Uninsulated
Pipe Dia.
2 ½
3
in.
20
10
50
Winter
0
10
20
Design
-20
10
10
Temp
°F
-40
10
5
Maximum Allowable Exposed Vent Length in Unconditioned Space (Metric)
Unit Size
Uninsulated
Pipe Dia.
38
51
mm
-7
6.1
6.1
Winter
-18
3.0
1.5
Design
-29
1.5
Temp
°C
-40
Unit Size
Pipe Dia.
38
mm
-7
4.6
12.2
Winter
-18
4.6
Design
-29
4.6
Temp
°C
-40
3.0
Unit Size
Pipe Dia.
51
mm
-7
6.1
Winter
-18
6.1
Design
-29
4.6
Temp
°C
-40
3.0
Unit Size
Uninsulated
Pipe Dia.
64
76
mm
-7
3.0
15.2
Winter
-18
3.0
6.1
Design
-29
3.0
3.0
Temp
°C
-40
3.0
1.5
* Pipe length (ft) specified for maximum pipe lengths located in unconditioned spaces. Pipes located in unconditioned space cannot exceed total allowable pipe
length calculated from Table 16.
† Insulation thickness based on R value of 3.5 per in.