thermostat contolled attic fans

Cohiba · 05-13-2011, 01:14 PM

do thermostat contolled attic fans really work? worth the money? to lower A/C costs and to keep even temperature to keep heat expansion/contraaction at minimum to avoid noisy popping sounds?

Thurman · 05-13-2011, 01:21 PM

From what I have read and experienced with these type fans: They do work to move air through the attic area if the attic area is configured properly. They DO NOT work with ridge vents, understandably. IF you have both soffit venting and gable vents, they do not work efficiently as they will draw air from the source of least resistance. I have come across this situation and shown the homeowner the inefficiency of this. Blocking off the gable vents improved air flow via the soffit venting. One thing I will say: Most of these units have no provisions to shut off power IF the motor locks up, which is common with these. There have been a number of home fires in my area which were ruled as caused by these attic fan motors "locking up", then overheating and starting the fire. When I install, or replace a motor on, these I also add an inline fuse just for the fan motor. Depending on a circuit breaker, which may/probably has, other applications just is not safe to me.

Cohiba · 05-13-2011, 01:44 PM

i only have soffit vents around the house - anything you would recommens. the solar ones, whirly bird, etc.?

High Gear · 05-14-2011, 12:48 PM

Ridge vent is all you need.

+1 on the house fires , I would never use an attic vent , passive is the way to go.

vsheetz · 05-14-2011, 01:20 PM

Don't mean to hijack but rather spur the discussion

Thread is of interest to me due to a room addition project nearing. 16x26 master bedroom with 4/12 tiled roof. SoCal where summer hits 90 degree plus easy - winter nights coldest is usually 40 or so.

Planning currently for two O'Hanlin vents centered high On either side of the ridge and a solar powered fan exhausting through gable end vent. No eave/soffit vents allowed due to fire zone codes. Insulation in 2x6 walls of R20 or more and ceiling with R40 or so. HVAC via mini split heat pump / AC unit.

CA title-24 compliance needed.

Thoughts / comments?

Cohiba · 05-14-2011, 01:47 PM

What about solar fan ? Or whirlybird birds? Or other?

High Gear · 05-14-2011, 01:53 PM

No moving parts , ridge vent is pretty much foolproof.

Cohiba · 05-14-2011, 01:57 PM

My roof is flat with soffits all around

vsheetz · 05-14-2011, 02:13 PM

Quote:

Originally Posted by Cohiba

My roof is flat with soffits all around

If flat roof, what is the space and size that needs ventilation? If flat sounds like there won't be much natural air movement via convection..

Where are you located?

I am planning for the solar all purpose ventilator from:
http://www.ussunlight.com/products/solar-attic-fans
Other models and info on their website.

Cohiba · 05-14-2011, 02:16 PM

Live in warm climate, over 100 degrees in summer. Trying to both lower ac expense and quiet heat expansion and contractio noise in attic. Familiar with this?

vsheetz · 05-14-2011, 02:35 PM

Quote:

Originally Posted by Cohiba

Live in warm climate, over 100 degrees in summer. Trying to both lower ac expense and quiet heat expansion and contractio noise in attic. Familiar with this?

Very familier with ac expense

but never had noises from heat expansion and contraction - have lived in hot southern climes most all my life and through several houses. I can see where flat roof can get very hot due to no nature convenction air flow - hot air rises, but if flat you have no where for it to go. So some sort of powered ventilator may well be a good thing. I like the solar powered fan units.

More details of your roof construction, insulation, and attic space may help folks to help you better.

CDH · 05-14-2011, 10:31 PM

I installed a power ventilation attic fan and it keeps my attic at around 100 degrees in the heat of the Florida summer, had 3 off ridge vents and unless there was a pretty good wind blowing you could feel very little air coming out of them and attic temps got up to around 130+, I have not closed off my off ridge vents and my attic stays 30 degrees cooler so I believe they do as advertised.

Giles · 05-15-2011, 12:43 PM

Quote:

Originally Posted by Thurman

From what I have read and experienced with these type fans: They do work to move air through the attic area if the attic area is configured properly. They DO NOT work with ridge vents, understandably. IF you have both soffit venting and gable vents, they do not work efficiently as they will draw air from the source of least resistance. I have come across this situation and shown the homeowner the inefficiency of this. Blocking off the gable vents improved air flow via the soffit venting. One thing I will say: Most of these units have no provisions to shut off power IF the motor locks up, which is common with these. There have been a number of home fires in my area which were ruled as caused by these attic fan motors "locking up", then overheating and starting the fire. When I install, or replace a motor on, these I also add an inline fuse just for the fan motor. Depending on a circuit breaker, which may/probably has, other applications just is not safe to me.

I have 5 "pancake style" power vent fans. All are "Thermal Overload Protected"---Why would someone need additional protection with inline fuse.
Also--what size fuse would you recommend?