Handbook of air conditioning and refrigeration / Shan K

TABLE 6.4 CLTD for Calculating Sensible Cooling Loads from Flat Roofs, °F
6.27
Solar time, h
Description of Weight, U value,
construction lb/ft 2 Btu/h�ft 2 �°F 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Without suspended ceiling
2.5-in. wood with
2-in. insulation
13 0.093 30 26 23 19 16 13 10 9 8 9 13 17 23 29 36 41 46 49 51 50 47 43 39 35 19 8 51 43
4-in. wood with
2-in. insulation
18 0.078 38 36 33 30 28 25 22 20 18 17 16 17 18 21 24 28 32 36 39 41 43 43 42 40 22 16 43 27
With suspended ceiling
1-in. wood with
2-in. 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
2.5-in. wood with
1-in. 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-in. 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
4-in. heavyweight 54
concrete with
2-in. insulation
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
2.5-in. wood with
2-in. 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
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 33 22 11
6-in. heavyweight 77
concrete with
2-in. insulation
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
4-in. wood with 19 0.082 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
2-in. insulation 20 0.064
Conditions of direct application and adjustments are stated in the text.
Source: Abridged with permission from ASHRAE Handbook 1989, Fundamentals.
Hours of
maximum Minimum Maximum Difference
18 19 20 21 22 23 24 CLTD CLTD CLTD in CLTD