Configuring Attic Ventilation Based On Outside Temperture

In these instances systems have a harder time maintaining the desired temperature.

Configuring attic ventilation based on outside temperture. Then stack effect is the prime air mover driven by the attic to outside air temperature difference. Luckily my wife and i were upstairs and hear the rafters crackling looked outside and saw the wall of fire and got our. Lowering the temperature in the attic can lower the temperature in the rest of the home reducing the amount of time the home s air conditioner spends running. So my house burned down a couple of years ago.

Attic fans draw cooler outside air into the hot attic area through attic vents located either on the roof or on the wall near the gable to reduce the space s temperature. In the summer time a well ventilated attic helps to keep the attic cooler. In the summertime the outdoor air temperature as well as the air inside the attic is warmer than it is in the winter and warmer air can hold more moisture than cold air can. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents.

The fire started on an outside wall went up the wall and into the attic space spread across the entire house in the attic with no smoke coming into the house until the ceiling was about to collapse which was far too late. Therefore the greatest need for attic ventilation is when there is little wind pressure to force air in and out of the attic. As figure 1 demonstrates if the outside air is 32 c 90 f and 70 percent rh it is drier than interior attic space which is 43 c 110 f at 40 percent or higher rh. A well ventilated attic helps to avoid problems with moisture and heat buildup.

Be it winter or summer the goal is to keep the ventilated attic as close as possible to the outside temperature. This design is less efficient when hvac equipment and ductwork is in the attic space. Attic temperature depends on the amount of solar radiation construction details and the rate of ventilation. Calculations indicate that on a july day in texas a ventilation rate of one air change per minute for a typical attic using 95 degree f air will lower the peak attic temperature to about 101 degrees f.

If your attic soars above 100 degrees and reaches the 150 mark its time to consult professionals. A standard powered exhaust vent turns on when the temperature inside the attic. Providing half air change per minute will lower the temperature to about 106 degrees f.