LEAFLET NO. 63JUE95 COOLER HOMES ho~an ATTIC VENTILATION WALTER GRUB, Assatae Agritural Engineer A TTIC VENTILATION and ceiling insuil- ation can make your house cooler during the hot summer months. ]Results of research at the Agricul- tural Experiment Station of The Ala- bama Polytechnic Institute, show that high ceiling temperatures can be low- ered by insulating the ceiling and re- moving hot air trapped in the attic. These control measures are especially important because attic air, sometimes 1L The study was in cooperation with the Southern Rcsearch Housing Pro- ject S-8. 300 higher than outside air, heats the ceilings of the roo-ms below. Thus, they become undesirable heating panels for occupants of the rooms. TEST DESCRIPTION and RESULTS First year. Various types of attic ventilation systems xxvere installed in a series of identical test roofs to check their effects on ceiling surface tempera- tures. These systems were gable end louvers, a ridge louver, a flue, and a fan. A fifth roof xxas completely closed an(1 used as a check. IIP Above ore three of the battery of various attic types used in the Experiment Station study to determine the best system for lowering ceiling temperature. AGRICULTURAL EXPERIMENT STATION 4THE ALABAMA POLYTECHNIC INSTITUTE JUNE 1959 E. V. Smith, Director Auburn, Alabama TABLE 1. CEILING SURFACE TEMPERATURES WITHDIFFERENT VENTILATION SYSTEMS, AUGUST 25, CLEAR DAY Temperature at different times of day (degrees Farenheit) Ventilation 8 9 10 11 12 1 2 3 4 5 system a.m. a.m. a.m. a.m. m. p.m.p.m.p.m.p.m.p.m. Outside temperature --__ 88 90 94 97 97 97 100 98 97 94 Closed attic - ---------- 84 99 107 114 117 118 117 117 114 110 Ridge louver---------82 92 98 102 104 106 106 105 103 100 Flue ---------------------------81 93 97 103 103 104 107 105 103 99 Fan ----------- 85 92 96 98 98 100101100 98 96 Gable louvers 85 95 100 106 107 108 109 107 104 102 1 Temperatures given are typical of others recorded during test period. There was no insulation on upper surface of ceiling. The fan, which produced one air change per minute, was the most effec- tive system for lowering the ceiling surface temperature, Table 1. The ridge louver was second followed by the flue and gable end louvers. The completely closed attic produced the hottest ceiling surface. When insulation was applied to the upper ceiling sur- face, the temperature differential be- tween systems decreased. However, the effectiveness of the various attic space ventilation systems remained in the same order. Second year. Following the first summer tests, the roofs were modified. Fans of different sizes were installed in four roofs. The fifth roof remained closed. The fans were rated to produce 1, 2, 332, and 512 attic air changes per minute. The last two rates were se- lected to correspond with summer room ventilation systems of % and 1 air change per minute for a one-story house with 8-foot ceilings. Expanded vermiculite insulation was applied to areas of the ceilings of each test roof at thickness of 1 and 2 inches. Results of these studies show that the greater the rate of ventilation, the lower the ceiling surface temperature. It can be readily seen from Table 2 that the greatest difference in ceiling surface temperatures was between the unventilated attic and the attic with one air change per minute. The greater ventilation rates produced a cooler ceil- ing, but the reduction of temperature was not in proportion to the increased rate of air movement. The data also show that a cooler ceiling surface was obtained with the heaviest rate of in- sulation, Table 3. However, the great- est temperature reduction was from the no insulation to the 1-inch application. The diagram illustrates attic ventilation system that gave good results in the tests. Arrows show movement of air pulled by fan through louvers. TABLE 2. CEILING SURFACE TEMPERATURES WITH DIFFERENT VENTILATION RATES, AUGUST 27, CLEAR DAY1 Temperatures at different times of day (degrees Farenheit) Ventilation 7 8 9 10 11 12 1 2 3 4 5 rate a.m. a.m. a.m. a.m. a.m. m. p.m. p.m. p.m. p.m. p.m. Outside temperature __ 78 82 87 89 92 93 96 98 100 96 93 Closed attic . 71 76 85 90 96 102 106 107 109 109 107 1 air change - 71 76 84 88 92 96 98 99 101 100 98 2 air changes ---- 72 77 84 87 91 95 96 98 99 99 96 3.1 air changes -- 72 76 84 87 91 95 97 97 99 98 96 5/2 air changes ---- 71 76 82 86 90 93 96 96 98 97 95 1 Temperatures given are typical of others recorded during test period. There was no insulation on upper surface of ceiling. TABLE 3. CEILING SURFACE TEMPERATURES WITH DIFFERENT INSULATION DEPTHS, AUGUST 27, CLEAR DAY Insulation Temperatures at different times of day (degrees Farenheit) depth in 7 8 9 10 11 12 1 2 3 4 5 inches a.m. a.m. a.m. a.m. a.m. m. p.m. p.m. p.m. p.m, p.m. Outside temperature .- 78 82 87 89 92 93 96 98 100 96 93 Closed attic 0 ------------ 71 76 85 90 96 102 106 107 109 109 107 1 ------------ 72 75 82 85 89 94 97 98 100 101 101 2 ------------ 72 75 82 84 88 92 95 96 98 99 100 1 air change per minute 0 ------------ 71 76 84 88 92 96 98 99 101 100 98 1 ------------ 71 75 81 84 87 91 93 95 97 97 96 2 -------------- 71 75 81 84 87 90 91 92 95 95 95 CONCLUSIONS change per minute, and should be As a result of these studies and ob- operated continuously when attic tem- servations, the following conclusions perature is higher than outside temper- are drawn: ature. 1. Anraw3. Insulation placed on the upper 1. An attic exhaust fan will reduce surface of the ceiling will hold the ceiling surface temperature during the ceiling at a lower temperature. summer months. 4. At least 2 inches of insulation is 2. The attic exhaust system should needed for summer and winter temper- move air at the rate of at least one air ature control.