Attic Fan

dpg · 04-12-2011, 06:09 AM

Does anyone have a roof mounted attic fan in their home? What do you think of it, do they truely work at keeping the attic cooler in the heat? Any specific brand recommendations (I do not want run-of-the-mill "big box" quality.) And one more thing, should I go electric or solar? I'm just concerned about solars dependability. Also, any "whole house" fan owners out there? What do you think of them?

MikeF-NH · 04-12-2011, 06:36 AM

We have a house fan mounted on our second floor ceiling and it does a great job at keeping our house cool. We haven't used AC for a few years now as the fan keeps a nice breeze going through the entire house. To get a good draft going though, we close all windows on the second floor until about an hour before we go to bed so that air is drawn from the downstairs windows through the entire house. Before bed time, we open the upstairs windows to suck and hot air out of the bedrooms. It is a bit loud but I imagine newer fans are much quieter.

tis · 04-12-2011, 06:37 AM

We put a solar powered fan in our basement and it works great. I don't know what kind it is.

MarkinNH · 04-12-2011, 06:45 AM

My only knowledge is with a whole house fan, not with a roof mounted attic fan. So my experience may be of No benefit to you. My BIL had one installed in his house on Moultonborough Neck Road, in the ceiling of the hallway at the 2nd floor landing. It was the whole house type with the automatic louvers and belt driven motor, approx. 3' sq. His only exhausted into the attic and not directly to the outside.
It worked so well that in the late afternoon / evening as the sun would be going down, he could turn on the fan and open ANY window in the house, even just a few inches, (we experimented) and you could instantly feel a breeze moving through the house. The more you opened a window or windows the bigger the breeze would get. I was pretty impressed.
I am sure some of it's great performance was due to it's location, the layout of the house etc. When he built his house, the fan was part of his overall plan, so there was adequate ventilation added so that all this extra air could then escape the attic via ridge and gable vents
So, due to that experience alone, I think "Whole house Fan" are a great idea.
Given the amount of air one of the fans can move I can't imagine how a roof mounted exhaust fan wouldn't work well in cooling an attic, as long as it can pull adequate cooler or fresh air from either outside or through the house itself.

chipj29 · 04-12-2011, 06:55 AM

We have a whole house fan. It works great, really moves the air around...but...

Our house is a ranch. Here is how it works. The attic tends to get real hot, which in turn makes the house hot. So we turn on the whole house fan and open the windows. Well, I think my attic ventilation might be a bit inadequate, because the whole house fan blows the hot attic air out the soffits. Again, the house is a ranch so all the windows are right under the soffits. The whole house fan creates a nice breeze throughout the house...but it sucks in that nice hot air that just got blown out the attic soffits.

I need a roof top attic fan like you. Something...anything to help vent the attic a bit better.

lakershaker · 04-12-2011, 07:13 AM

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.

dpg · 04-12-2011, 07:36 AM

Quote:

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 · 04-12-2011, 08:25 AM

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 · 04-12-2011, 08:26 AM

Quote:

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 · 04-12-2011, 08:40 AM

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 · 04-12-2011, 10:36 AM

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 · 04-12-2011, 10:45 AM

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 · 04-12-2011, 11:37 AM

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!

MarkinNH · 04-12-2011, 11:56 AM

Quote:

Originally Posted by chipj29

We have a whole house fan. It works great, really moves the air around...but...

Our house is a ranch. Here is how it works. The attic tends to get real hot, which in turn makes the house hot. So we turn on the whole house fan and open the windows. Well, I think my attic ventilation might be a bit inadequate, because the whole house fan blows the hot attic air out the soffits. Again, the house is a ranch so all the windows are right under the soffits. The whole house fan creates a nice breeze throughout the house...but it sucks in that nice hot air that just got blown out the attic soffits.

I need a roof top attic fan like you. Something...anything to help vent the attic a bit better.

Can you duct the air from the fan over to a large gable end vent ?
A HVAC company could probably put something togther easily. A homeowner cheap yankee way would be to construct a light weight plywood box to sit over the fan and a suitable length of large flex duct (solid sheet metal would work better) like an HVAC company would use for a cold air return, snaked over to a gable end vent would direct the air away from the soffits.

Kamper · 04-12-2011, 02:21 PM

I installed an attic fan with a thermostat switch and a bypass switch. I did this because I was told it would it would help extend the life of my shingles. Since then I went with a new roof anyway... I do throw on the by-pass if I need to be up there more than a few minutes.

A friend of mine had what the seller told her was a "whole house fan." It looked like a shutterred door mounted in the ceiling. I'm sure newer (or cleaner...) models are much quieter than hers was. This one sounded like a coal-mine ventilator. Also the house was perhaps too tight because it must have been drawing air back down through her chimney, sometimes the smoke alarm would go off if she didnt have a window open.

lawn psycho · 04-12-2011, 02:36 PM

We had a whole house fan built into the ceiling of our central upstairs hallway and wow does it do a good job of keeping the temps down.

All our interior walls are insulated and have sound batting so the builder recommended we vent the house or it could be steamy in summer. Good call on his part. I have no clue what brand it is but ours has the louvers and we have a switch in the hall to turn the fan on/off.

Make sure you have easy access as in winter I have to climb in the attic and place an included insulating blanket/cover over the fan to prevent warm arm from escaping. The builder also put several bats of insulation in the attic as added insulation over the cover. We have batted insulation with blown-in insulation on top of that in our attic so I have to be careful when up there since you can't see the joists.

NoBozo · 04-12-2011, 06:10 PM

Quote:

Originally Posted by Kamper

This one sounded like a coal-mine ventilator. Also the house was perhaps too tight because it must have been drawing air back down through her chimney, sometimes the smoke alarm would go off if she didn't have a window open.

One of my pet peeves has been the PUSH to replace your perfectly good OLD windows with "Energy Efficient" ..TIGHT windows. ....BULL.

Think about it: Your house needs to Breathe and refresh itself. If it doesn't, you will have moisture problems....AND the air in the house will become increasingly Polluted, since the air in the house doesn't change out often enough.

WHO wants Polluted Air in their home..? Just sayin...

NB

Grady223 · 04-18-2011, 09:11 AM

Quote:

Originally Posted by dpg

Does anyone have a roof mounted attic fan in their home? What do you think of it, do they truely work at keeping the attic cooler in the heat? Any specific brand recommendations (I do not want run-of-the-mill "big box" quality.) And one more thing, should I go electric or solar? I'm just concerned about solars dependability. Also, any "whole house" fan owners out there? What do you think of them?

Sounds like you are trying to keep the attic cool (ventilation fan) versus cooling the whole house (whole house fan).

I have installed and used both.

They now make ventilation fans that operate on photo cells mounted on its cap - easy to install - no electrical hook ups. A friend has one and it works great. As far as their overall value - they are well worth the money - they really keep the AC costs down.

Whole house fans do cool the whole house as long as the temp is cooler outside than in - they also pull in the humidity. Sometimes keeping the windows closed on a hot day works better as the house never has a chance to heat up. We have the following unit in our island home (http://www.tamtech.com/store/hv1000-...on,Product.asp), works great under the proper circumstances but nothing but AC helps on a hot humid night.

04-12-2011, 06:09 AM	#1
dpg Senior Member Join Date: Apr 2004 Posts: 2,560 Thanks: 149 Thanked 229 Times in 166 Posts	Attic Fan Does anyone have a roof mounted attic fan in their home? What do you think of it, do they truely work at keeping the attic cooler in the heat? Any specific brand recommendations (I do not want run-of-the-mill "big box" quality.) And one more thing, should I go electric or solar? I'm just concerned about solars dependability. Also, any "whole house" fan owners out there? What do you think of them?

04-12-2011, 06:55 AM	#5
chipj29 Senior Member Join Date: Apr 2004 Location: Bow Posts: 1,874 Thanks: 521 Thanked 308 Times in 162 Posts	We have a whole house fan. It works great, really moves the air around...but... Our house is a ranch. Here is how it works. The attic tends to get real hot, which in turn makes the house hot. So we turn on the whole house fan and open the windows. Well, I think my attic ventilation might be a bit inadequate, because the whole house fan blows the hot attic air out the soffits. Again, the house is a ranch so all the windows are right under the soffits. The whole house fan creates a nice breeze throughout the house...but it sucks in that nice hot air that just got blown out the attic soffits. I need a roof top attic fan like you. Something...anything to help vent the attic a bit better. __________________ Getting ready for winter!

04-12-2011, 07:13 AM	#6
lakershaker Senior Member Join Date: Jul 2004 Location: Rattlesnake Isl. - Simsbury, CT Posts: 271 Thanks: 90 Thanked 44 Times in 26 Posts	Attic fan 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.

04-12-2011, 08:25 AM	#8
upthesaukee Senior Member Join Date: Jan 2003 Location: Alton Bay Posts: 5,547 Blog Entries: 2 Thanks: 2,397 Thanked 1,918 Times in 1,061 Posts	Whole house fan in Louisiana 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 ! __________________ I Live Here... I am always UPTHESAUKEE !!!!

04-12-2011, 08:40 AM	#10
camp guy Senior Member Join Date: Apr 2004 Location: formerly Winter Harbor, still Wolfeboro Posts: 1,134 Thanks: 284 Thanked 480 Times in 271 Posts	attic fan 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.

04-12-2011, 06:36 AM	#2
MikeF-NH Senior Member Join Date: Apr 2009 Posts: 317 Thanks: 2 Thanked 120 Times in 80 Posts	We have a house fan mounted on our second floor ceiling and it does a great job at keeping our house cool. We haven't used AC for a few years now as the fan keeps a nice breeze going through the entire house. To get a good draft going though, we close all windows on the second floor until about an hour before we go to bed so that air is drawn from the downstairs windows through the entire house. Before bed time, we open the upstairs windows to suck and hot air out of the bedrooms. It is a bit loud but I imagine newer fans are much quieter.

04-12-2011, 06:37 AM	#3
tis Senior Member Join Date: Jan 2006 Posts: 6,405 Thanks: 719 Thanked 1,379 Times in 955 Posts	We put a solar powered fan in our basement and it works great. I don't know what kind it is.

04-12-2011, 06:45 AM	#4
MarkinNH Senior Member Join Date: Mar 2010 Posts: 392 Thanks: 177 Thanked 146 Times in 76 Posts	My only knowledge is with a whole house fan, not with a roof mounted attic fan. So my experience may be of No benefit to you. My BIL had one installed in his house on Moultonborough Neck Road, in the ceiling of the hallway at the 2nd floor landing. It was the whole house type with the automatic louvers and belt driven motor, approx. 3' sq. His only exhausted into the attic and not directly to the outside. It worked so well that in the late afternoon / evening as the sun would be going down, he could turn on the fan and open ANY window in the house, even just a few inches, (we experimented) and you could instantly feel a breeze moving through the house. The more you opened a window or windows the bigger the breeze would get. I was pretty impressed. I am sure some of it's great performance was due to it's location, the layout of the house etc. When he built his house, the fan was part of his overall plan, so there was adequate ventilation added so that all this extra air could then escape the attic via ridge and gable vents So, due to that experience alone, I think "Whole house Fan" are a great idea. Given the amount of air one of the fans can move I can't imagine how a roof mounted exhaust fan wouldn't work well in cooling an attic, as long as it can pull adequate cooler or fresh air from either outside or through the house itself.

04-12-2011, 10:36 AM	#11
dpg Senior Member Join Date: Apr 2004 Posts: 2,560 Thanks: 149 Thanked 229 Times in 166 Posts	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???

04-12-2011, 10:45 AM	#12
NoBozo Senior Member Join Date: Jun 2008 Location: Portsmouth. RI Posts: 2,231 Thanks: 400 Thanked 460 Times in 308 Posts	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

04-12-2011, 11:37 AM	#13
chipj29 Senior Member Join Date: Apr 2004 Location: Bow Posts: 1,874 Thanks: 521 Thanked 308 Times in 162 Posts	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! __________________ Getting ready for winter!

04-12-2011, 02:21 PM	#15
Kamper Senior Member Join Date: Jul 2005 Location: Thornton's Ferry Posts: 1,296 Thanks: 67 Thanked 166 Times in 126 Posts	I installed an attic fan with a thermostat switch and a bypass switch. I did this because I was told it would it would help extend the life of my shingles. Since then I went with a new roof anyway... I do throw on the by-pass if I need to be up there more than a few minutes. A friend of mine had what the seller told her was a "whole house fan." It looked like a shutterred door mounted in the ceiling. I'm sure newer (or cleaner...) models are much quieter than hers was. This one sounded like a coal-mine ventilator. Also the house was perhaps too tight because it must have been drawing air back down through her chimney, sometimes the smoke alarm would go off if she didnt have a window open.

04-12-2011, 02:36 PM	#16
lawn psycho Senior Member Join Date: Jul 2009 Location: On the move... Posts: 987 Thanks: 113 Thanked 248 Times in 133 Posts	We had a whole house fan built into the ceiling of our central upstairs hallway and wow does it do a good job of keeping the temps down. All our interior walls are insulated and have sound batting so the builder recommended we vent the house or it could be steamy in summer. Good call on his part. I have no clue what brand it is but ours has the louvers and we have a switch in the hall to turn the fan on/off. Make sure you have easy access as in winter I have to climb in the attic and place an included insulating blanket/cover over the fan to prevent warm arm from escaping. The builder also put several bats of insulation in the attic as added insulation over the cover. We have batted insulation with blown-in insulation on top of that in our attic so I have to be careful when up there since you can't see the joists.