At what temperature should I set my attic power vent fans to keep my attic cool? I live in a hot and humid climate, where temperatures are often in the 90s. The roof gets full exposure to the sun throughout the day.
Our Answer
Attic ventilators generally turn on between 90 and 110 degrees Fahrenheit. That said, attic fans are not the best choice for cooling attics, especially if you have central air conditioning. The reason is that attic fans depressurize attics and can rob air conditioned air from the main body of the house, greatly decreasing efficiency. It essentially pulls that cooled air through cracks and crevices in the attic floor, and also through holes that allow for wires and pipes.
A much better cooling option is continuous ridge and soffit venting. Basically, you cut a slot in the top ridge of the roof and put a vent right over it. As the wind blows over the roof, it depressurizes the ridge and sucks the moist warm air from the attic. Everything you want to vent from the attic gets sucked out of that ridge through the depressurization that happens through the normal wind cycle.
We have a new 2022 well insulated (R30) and sealed single-story house with continuous ridge and soffit ventilation. At 88F outside the attic is measuring125F. Since we have no basement the HVAC system and ductworks are in the attic. Is this acceptable? Any suggestions?
At what temperature should an attic fan turn OFF? The other evening, ours ran until 1 am. At that point in time, the outside temperature was 59F and the attic temperature was 61F. This seems to me the fan is running for an entirely unnecessary length of time. I should mention that recently the fan would run, shut down for the evening, then restart for about 45 seconds, shut down for 45 seconds, etc., up to 4 or 5 times. My husband blew out an area he thought maybe bugs were in and that problem resolved. The fan now shuts off properly and stays off until the next day. It’s my opinion it just doesn’t shut down at the proper temperature.
Nancy, the attic fans should not be running at the temperature you’re reporting. They should come ON at 90 – 115 degrees and then go OFF as soon as the temperature in the attic drops below that number. It sounds’ to me like you need a new attic fan or at least a new attic fan thermostatic switch, although that may not be worth the effort to replace outside of the whole fan.
Ridge vents Suck and NOT in a good way (yes, I still have ridge vents ). Soffit to ridge drafting not very effective in areas with very little breeze and I agree with the previous comment that they often get blocked. You CAN have as many as 2 powered vents set at about 95-105 degrees and add boosters and Filtered outside air exchangers to assure your air stays about .08 positive so you are not sucking in outside air and humidity via unconditioned air. In the case of those unfortunate souls with second story attic AC units often over garages etc. it makes even MORE sense . Point is air removed must be replaced ,and you have to be mindful of where it comes from , how it is conditioned , and that at minimum it matches whats being withdrawn.
Rick, totally agree that some ridge vents are highly ineffective (my #1 personal dislike are that kind that look like plastic corrugated cardboard!). However, I’ve found that the AirVent, Inc models are very effective. Take a look at the ShingleVent II Ridge Vent. These have external wind baffles that speed up depressurization at the ridge and deflects wind and weather.
We had a ridgevent installed & turtle vents removed AND we ended up with MOLD in our attic & several leaks on house ceilings due to condensation.
NOT HAPPY!
Evidently Ridge Vents need an assist sometimes?
Kathy, Ridge vents need to be coupled with continuous perforated soffit vents for the system to work. Soffit vents are often blocked by insulation over stuffed at the exterior wall, and I have also many times found ventilated soffit panels installed OVER solid plywood soffits, which of course completely defeats the purpose. Also, some ridge vents, particularly the ones that are plastic but look like corrugated cardboard don’t function very well as they will not pass enough air. This technology works, so I would look further to find out why its not functioning normally in your home.