[bob22]

I think most would say to add in soffit vents and get rid of the roof fan if that is what is meant by attic fan. But, I would think if you set it for 115 or so it would bring down the temp theoretically reducing the load on the ac system. You are fighting natural tendency of hot air to rise and exit the ridge vents by what you are planning.
See:
http://www.greenbuildingadvisor.com...nce/are-solar-powered-attic-ventilators-green
http://www.energystar.gov/index.cfm?c=diy.diy_attic_ventilation
http://www.factsfacts.com/MyHomeRepair/ventilation.htm
The main point of most of these is: "Although attic ventilation has been shown to reduce attic air temperatures and cooling loads the only examination of powered attic ventilators has shown the electricity consumption of the ventilator fans to be greater than the savings in air conditioning energy (Burch et al., 1979)." Especially if attic is R19 or higher. Fixing air leakage from conditioned space into attic would be a great move to reduce costs if the attic space is negatively pressured (from gable fan running) and drawing conditioned air into the attic.

 

[DToynk]

Unfortunately soffit vents are not an option. My attic is only 1000 sq ft and I have a window on each side. Do you think if i keep both windows open will this be enough airflow with my ridge vents? Also if I try this I was just thinking of monitoring the temperature, so what would a decent temp in the attic be on a 90 degree day?
thanks
Dave

 

[alecmcmahon]

I think most manufactures recommend attic fan t-stats to be 105 to 115

I have mine set at 105

 

[Technow]

With ridge vents I would be more inclined to have a fan in the windows blowing in.

Don't know why soffit vents are not an option but they make ridge vents work the best especially with some foil on the rafters.

 

[josephthomas199]

i have a similar issue, i cant install soffet vents cause my attic is sectionated or compartmentalized, so even if i installed soffet vents the cool air wont reach the ridge vent. what should we doo???