Attic Fan

[dpg]

Originally Posted by lakershaker

We put in an attic fan because of poor roof ventilation with the ridge vent. This combined with not enough attic insulation caused us to have a moisture problem in the attic. The fan we had installed has both a temperature switch and a humidifier switch, so if it gets too hot or too moist it turns on. Combined with the addition of blown in insulation, we noticed a huge improvement in both heating and AC costs, and didn't have the horrible moisture problem. Don't remember the name of the fan unit, but it was hard wired to electric and was only about 8" diameter.

I'm looking into exactly what you have done. In the middle of quoting blown in insulation also, the same company recommended an attic fan and said the whole house fans are nice also. Thanks all they definitely both sound like a "go."

[upthesaukee]

We had one down there, and our ranch style house had a cupola on the roof over the fan. Because of the humidity down there, the fan was used more in the spring and fall, not so much in the summer.

We found that opening the windows about 2 inches (casement type about 2.5 ft high) in the bedrooms was about the best airflow. Much more than that and the airflow actually seemed to decrease. During the day, we would close the bedroom windows to just a crack, and open the windows in the den and dining room and had a good flow through the rest of the house. Bedtime, reversed it, opening the bedroom windows and closing down the den and dining room.

Loved the fan. Love to have one in our house, but not practical at all.

Comments on proper attic ventilation is right on. We were in homes down there that had two wind turbines on roof, and they couldn't keep up with the whole house fan. Watching Holmes on Homes on HGTV, he will often talk about improper ventilation in attics, and a lot of it deals with soffits blocked by insulation and inadequate roof vents.

I am not a contractor (I use a large hammer to drive in the screw to hang a picture) but experience and shows like HoH shows that a proper fan with proper ventilation yields the best results. Good luck with your project, and be !

[jmen24]

Originally Posted by dpg

I'm looking into exactly what you have done. In the middle of quoting blown in insulation also, the same company recommended an attic fan and said the whole house fans are nice also. Thanks all they definitely both sound like a "go."

One thing to think about if you are going to combine a whole house fan and an attic fan is that the whole house fan will move a lot more air than the attic fan. Thus, when the whole house fan is running and the attic fan feels the need to operate, it may free spin the attic fan faster than the motor is actually turning it. Can be very taxing on an electric motor. Similar to reving your car engine all the way to red line without any load (being in gear and moving).

Our customers that have the whole house fans, love them. In this area they really are a great way to keep things cool, without the need for an A/C. But the air has to be able to escape in an efficient fashion. ChipJ, get some larger gable vents installed. If the access is good to the attic, it should be an inexpensive option to get the most out of your fan. And by going bigger, the siding just needs to be cut to fit the new opening and not replaced or removed (unless it is vinyl, than removing and cutting is the best option, but still very easy).

[camp guy]

I would strongly second jmen24 comment to chipj to increase the venting from the attic using the largest gable end vents possible.

Cooling a house using fans is all about getting rid of the hotter air and replacing it with cooler air. To do this, you do not want any 'pressure' to build up when trying to evacuate hot air. Gable end vents and a ridge vent system work extremely well with both whole house fans and attic fans.

You probably want to have the whole house fan controlled by a switch, but I suggest an attic fan be controlled by a temperature switch, and having a manual override isn't a bad idea, either.

Good luck.

[dpg]

Again thanks and it sounds as thought you cannot go "to large" with an attic roof fan. Unlike say a window AC where bigger is not better. True???

[NoBozo]

We have a typical 24'x44' raised ranch with a "Hip Roof" with two 8'' box vents ..one on each end and no soffit or ridge vents... = Hot attic.

We also had a remote reading thermometer in the attic before and after we had a Master Flow attic fan installed. Before the fan, the temp in the attic in the afternoon would typically be 145+ degrees on sunny days in August. Without the forced ventilation that temp would pretty much remain until 5:00 AM the next morning. It was like a Hot Blanket above all the rooms in the house.

After we added the fan AND 16 soffit vents under the wide roof overhangs, the temp rarely goes over 107 degrees on the hottest days. The fan was less than $100 at Home Depot. We had the fan installed when the roof was re-shingled in 2003. The fan has a thermostat in the attic which turns the fan on at about 90 degrees and there is a manual shutoff switch in the utility room.

BTW: The old 8" box vents were Eliminated and we Did Not have "Ridge Vents" installed as they would interfere with the airflow with the new fan. NB


Hip Roof: http://en.wikipedia.org/wiki/Hip_roof

Master Flow: http://www.gaf.com/Roofing/Residenti...entilator.aspx

[chipj29]

Thanks jmen and campguy.
I have ridge vents running the length of the roof line, which is about 50'. There are gable vents on each end, and another gable vent over the overhang.
I think the prob with the gable vents is that they are very small. Just some slits in the aluminum siding. I have been wanting to install some bigger gable vents, now that I know it will help, I have the motivation!

Thanks again!