Unit Thermal Resistances Well Sealed Air Spaces

Heat Transfer Engineering
Thermodynamics
Engineering Physics

Unit thermal resistances (R-values) of well-sealed air spaces (from ASHRAE Handbook of Fundamentals, Ref. 1, Chap. 22, Table 2)

SI units (in m2 · °C/W)

Position
of Air
Space
Direction
of
Heat
Flow
Mean
Temp.
°C
Temp.
Diff.,
°C
20-mm Air Space
40-mm Air Space
90-mm Air Space
Effective Emissivity, εeff
Effective Emissivity, εeff
Effective Emissivity, εeff
0.03
0.05
0.5
0.82
0.03
0.05
0.5
0.82
0.03
0.05
0.5
0.82
Horizontal Up ↑
32.2
5.6
0.41
0.39
0.18
0.13
0.45
0.42
0.19
0.14
0.50
0.47
0.20
0.14
10.0
16.7
0.30
0.29
0.17
0.14
0.33
0.32
0.18
0.14
0.27
0.35
0.19
0.15
10.0
5.6
0.40
0.39
0.20
0.15
0.44
0.42
0.21
0.16
0.49
0.47
0.23
0.16
-17.8
11.1
0.32
0.32
0.20
0.16
0.35
0.34
0.22
0.17
0.40
0.38
0.23
0.18
45° slope Up ↑
32.2
5.6
0.52
0.49
0.20
0.14
0.51
0.48
0.20
0.14
0.56
0.52
0.21
0.14
10.0
16.7
0.35
0.34
0.19
0.14
0.38
0.36
0.20
0.15
0.40
0.38
0.20
0.15
10.0
5.6
0.51
0.48
0.23
0.17
0.51
0.48
0.23
0.17
0.55
0.52
0.24
0.17
-17.8
11.1
0.37
0.36
0.23
0.18
0.40
0.39
0.24
0.18
0.43
0.41
0.24
0.19
ertical Horizontal →
32.2
5.6
0.62
0.57
0.21
0.15
0.70
0.64
0.22
0.15
0.65
0.60
0.22
0.15
10.0
16.7
0.51
0.49
0.23
0.17
0.45
0.43
0.22
0.16
0.47
0.45
0.22
0.16
10.0
5.6
0.65
0.61
0.25
0.18
0.67
0.62
0.26
0.18
0.64
0.60
0.25
0.18
-17.8
11.1
0.55
0.53
0.28
0.21
0.49
0.47
0.26
0.20
0.51
0.49
0.27
0.20
45° slope Down ↓
32.2
5.6
0.62
0.58
0.21
0.15
0.89
0.80
0.24
0.16
0.85
0.76
0.24
0.16
10.0
16.7
0.60
0.57
0.24
0.17
0.63
0.59
0.25
0.18
0.62
0.58
0.25
0.18
10.0
5.6
0.67
0.63
0.26
0.18
0.90
0.82
0.28
0.19
0.83
0.77
0.28
0.19
-17.8
11.1
0.66
0.63
0.30
0.22
0.68
0.64
0.31
0.22
0.67
0.64
0.31
0.22
Horizontal Down ↓
32.2
5.6
0.62
0.58
0.21
0.15
1.07
0.94
0.25
0.17
1.77
1.44
0.28
0.18
10.0
16.7
0.66
0.62
0.25
0.18
1.10
0.99
0.30
0.20
1.69
1.44
0.33
0.21
10.0
5.6
0.68
0.63
0.26
0.18
1.16
1.04
0.30
0.20
1.96
1.63
0.34
0.22
-17.8
11.1
0.74
0.70
0.32
0.23
1.24
1.13
0.39
0.26
1.92
1.68
0.43
0.29

 

English units (in h · ft2 · °F/Btu)

Position
of Air
Space
Direction
of
Heat
Flow
Mean
Diff.
°F
Temp.
Diff.
°F
.75-in. Air Space
1.5-in. Air Space
3.5-in. Air Space
Effective Emissivity, εeff
Effective Emissivity, εeff
Effective Emissivity, εeff
0.03
0.05
0.5
0.82
0.03
0.05
0.5
0.82
0.03
0.05
0.5
0.82
Horizontal Up ↑
90
10
2.34
2.22
1.04
0.75
2.55
2.41
1.08
0.77
2.84
2.66
1.13
0.80
50
30
1.71
1.66
0.99
0.77
1.87
1.81
1.04
0.80
2.09
2.01
1.10
0.84
50
10
2.30
2.21
1.16
0.87
2.50
2.40
1.21
0.89
2.80
2.66
1.28
0.93
0
20
1.83
1.79
1.16
0.93
2.01
1.95
1.23
0.97
2.25
2.18
1.32
1.03
45° slope Up ↑
90
10
2.96
2.78
1.15
0.81
2.92
2.73
1.14
0.80
3.18
2.96
1.18
0.82
50
30
1.99
1.92
1.08
0.82
2.14
2.06
1.12
0.84
2.26
2.17
1.15
0.86
50
10
2.90
2.75
1.29
0.94
2.88
2.74
1.29
0.94
3.12
2.95
1.34
0.96
0
20
2.13
2.07
1.28
1.00
2.30
2.23
1.34
1.04
2.42
2.35
1.38
1.06
ertical Horizontal →
90
10
3.50
3.24
1.22
0.84
3.99
3.66
1.27
0.87
3.69
3.40
1.24
0.85
50
30
2.91
2.77
1.30
0.94
2.58
2.46
1.23
0.90
2.67
2.55
1.25
0.91
50
10
3.70
3.46
1.43
1.01
3.79
3.55
1.45
1.02
3.63
3.40
1.42
1.01
0
20
3.14
3.02
1.58
1.18
2.76
2.66
1.48
1.12
2.88
2.78
1.51
1.14
45° slope Down ↓
90
10
3.53
3.27
1.22
0.84
5.07
4.55
1.36
0.91
4.81
4.33
1.34
0.90
50
30
3.43
3.23
1.39
0.99
3.58
3.36
1.42
1.00
3.51
3.30
1.40
1.00
50
10
3.81
3.57
1.45
1.02
5.10
4.66
1.60
1.09
4.74
4.36
1.57
1.08
0
20
3.75
3.57
1.72
1.26
3.85
3.66
1.74
1.27
3.81
3.63
1.74
1.27
Horizontal Down ↓
90
10
3.55
3.29
1.22
0.85
6.09
5.35
1.43
0.94
10.07
8.19
1.57
1.00
50
30
3.77
3.52
1.44
1.02
6.27
5.63
1.70
1.14
9.60
8.17
1.88
1.22
50
10
3.84
3.59
1.45
1.02
6.61
5.90
1.73
1.15
11.15
9.27
1.93
1.24
0
20
4.18
3.96
1.81
1.30
7.03
6.43
2.19
1.49
10.90
9.52
2.47
1.62
Contribute Article
Spider Optimizer

© Copyright 2000 - 2017, by Engineers Edge, LLC www.engineersedge.com
All rights reserved
Disclaimer | Feedback | Advertising | Contact


User Reviews/Comments:

There are currently no comments available.


Add a Comment (you must be logged in to post comment Register):
Name:
Email: (Optional)
Comment: