CLTDs for flat roofs with suspended ceilings
From ASHRAE (1989), with permission
Click here to see CLTD values for roofs without
suspended ceilings.
Click here to see construction details for
the different roof types.
Roof No. |
Description of construction | Weight, lb/ft2 | U value, Btu/hr·ft2·°F | Solar time |
Hr of max. CLTD |
Min. CLTD |
Max. CLTD |
Diff. |
|||||||||||||||||||||||
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
||||||||
1 |
Steel sheet with 1" (or 2") insulation |
9 (10) | 0.134 (0.092) | 2 |
0 |
-2 |
-3 |
-4 |
-4 |
-1 |
9 |
23 |
37 |
50 |
62 |
71 |
77 |
78 |
74 |
67 |
56 |
42 |
28 |
18 |
12 |
8 |
5 |
15 |
-4 |
78 |
82 |
2 |
1" wood with 1" insulation |
10 | 0.115 | 20 |
15 |
11 |
8 |
5 |
3 |
2 |
3 |
7 |
13 |
21 |
30 |
40 |
48 |
55 |
60 |
62 |
61 |
58 |
51 |
44 |
37 |
30 |
25 |
17 |
2 |
62 |
60 |
3 |
4" lightweight concrete |
20 | 0.134 | 19 |
14 |
10 |
7 |
4 |
2 |
0 |
0 |
4 |
10 |
19 |
29 |
39 |
48 |
56 |
62 |
65 |
64 |
61 |
54 |
46 |
38 |
30 |
24 |
17 |
0 |
65 |
65 |
4 |
2" heavyweight concrete with 1" (or 2") insulation |
30 | 0.131 | 28 |
25 |
23 |
20 |
17 |
15 |
13 |
13 |
14 |
16 |
20 |
25 |
30 |
35 |
39 |
43 |
46 |
47 |
46 |
44 |
41 |
38 |
35 |
32 |
18 |
13 |
47 |
34 |
5 |
1" wood with 2 " insulation |
10 | 0.083 | 25 |
20 |
16 |
13 |
10 |
7 |
5 |
5 |
7 |
12 |
18 |
25 |
33 |
41 |
48 |
53 |
57 |
57 |
56 |
52 |
46 |
40 |
34 |
29 |
18 |
5 |
57 |
52 |
6 |
6" lightweight concrete |
26 | 0.109 | 32 |
28 |
23 |
19 |
16 |
13 |
10 |
8 |
7 |
8 |
11 |
16 |
22 |
29 |
36 |
42 |
48 |
52 |
54 |
54 |
51 |
47 |
42 |
37 |
20 |
7 |
54 |
47 |
7 |
2.5" wood with 1" insulation |
15 | 0.096 | 34 |
31 |
29 |
26 |
23 |
21 |
18 |
16 |
15 |
15 |
16 |
18 |
21 |
25 |
30 |
34 |
38 |
41 |
43 |
44 |
44 |
42 |
40 |
37 |
21 |
15 |
44 |
29 |
8 |
8" lightweight concrete |
33 | 0.093 | 39 |
36 |
33 |
29 |
26 |
23 |
20 |
18 |
15 |
14 |
14 |
15 |
17 |
20 |
25 |
29 |
34 |
38 |
42 |
45 |
46 |
45 |
44 |
42 |
21 |
14 |
46 |
32 |
9 |
4" heavyweight concrete with 1" (or 2") insulation |
53 (54) | 0.128 (0.090) | 30 |
29 |
27 |
26 |
24 |
22 |
21 |
20 |
20 |
21 |
22 |
24 |
27 |
29 |
32 |
34 |
36 |
38 |
38 |
38 |
37 |
36 |
34 |
33 |
19 |
20 |
38 |
18 |
10 |
2.5" wood with 2" insulation |
15 | 0.072 | 35 |
33 |
30 |
28 |
26 |
24 |
22 |
20 |
18 |
18 |
18 |
20 |
22 |
25 |
28 |
32 |
35 |
38 |
40 |
41 |
41 |
40 |
39 |
37 |
21 |
18 |
41 |
23 |
11 |
Roof terrace system |
77 | 0.082 | 30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
22 |
22 |
23 |
23 |
25 |
26 |
28 |
29 |
31 |
32 |
33 |
33 |
33 |
33 |
32 |
22 |
22 |
33 |
11 |
12 |
6" heavyweight concrete with 1" (or 2") insulation |
77 (77) | 0.125 (0.088) | 29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
21 |
22 |
23 |
25 |
26 |
28 |
30 |
32 |
33 |
34 |
34 |
34 |
33 |
32 |
31 |
20 |
21 |
34 |
13 |
13 |
4" wood with 1" (or 2") insulation |
19 (20) | 0.082 (0.064) | 35 |
34 |
33 |
32 |
31 |
29 |
27 |
26 |
24 |
23 |
22 |
21 |
22 |
22 |
24 |
25 |
27 |
30 |
32 |
34 |
35 |
36 |
37 |
36 |
23 |
21 |
37 |
16 |