Thermostat Temp For Attic Fan

[happymachinist]

Hey all, simple question, looking for input on what temp to set my attic thermostat as the title says.

We live in central Nebraska and the temps are going to be in the upper 90s the rest of the week, that's typical for summer highs around here.

It's a new to us house, and I'm putting in a new fan. Don't recall what the old one was set at and even if I did I've found enough questionable stuff around the house, not sure I'd trust the old setting.

Thanks!!

Sent from my XT1254 using Tapatalk

 

[csp]

Mine is set at 110 IIRC.

 

[engineer2]

Mine are set around 95-98.

 

[yeldogt]

Add more insulation in the ceiling .. and turn it off ........they waste energy. Do a google search.

 

[jayz66ragtop]

IIRC mine comes on at 90 and turns off when below 80 OR if the humidity is greater than 30%

Add more insulation in the ceiling .. and turn it off ........they waste energy. Do a google search.

This is why I got one that runs on both a solar panel and house power.

 

[engineer2]

Yes, they waste energy, but around here they are to make the shingles last longer... supposedly.

 

[gregtwojeeps]

I just installed a roof mount exhaust fan for my attic yesterday as it was getting 140 deg. F. in the attic on 85 deg. days. I was already seeing some curl on my black shingles from the excessive heat buildup. (bad color) I set the fan to come on at 100 deg. f....

I have a remote sensor for my 20 year old Radio Shack T-temperature monitor station hanging up in the attic also, just so I can keep an eye on the temps in the attic to be sure the fan is doing its job. The pics of the temps are of two minutes ago...

Be sure you have the proper intake ventilation to feed your ex. fan or you will be sucking too much of your air conditioned.... air out through your attic fan. ...

I found out the contractor that installed the vinyl clad soffits over the original plywood soffits on our 1959 ranch style house, did not put the perforated soffit vents over the existing soffit vent grilles = very little soffit air getting up to the attic. Spent the last two days getting that project re-done. Good luck .. jmo

 

[happymachinist]

Thanks everyone for the input.

The vents in the house are gable vents on the east and west side, the east side being powered.

The intake side on the west is quite a bit larger than the exhaust fan side, so I would think there would be plenty of flow.

I went up in the attic and it wasn't as warm as I thought it would be, the steel roof could be part of it, like I said the house is new to us.

As you suggested I did Google the use of powered attic vents and see the arguments against them, there are some valid points.





Sent from my XT1254 using Tapatalk

 

[Fixin'Stuff]

Gable vents aren't the best intake for cooling your attic. You're basically going to only be sucking air right across the ridge area and out the fan opening. Soffit vents draw cooler air across the entire underside of the roof deck. Cooler outside air comes in under the soffits and moves to the fan. Many attic-cooling articles that I've read suggest installing soffit vents and blocking off the gable vents.

 

[gregtwojeeps]

In the OP's case while noting the use of gable vents only, a fan will be necessary as an attic does not naturally vent well ....when the air has to flow horizontally through the attic. (think chimney flue) The best form of natural attic ventilation is for the air to go up through the soffit vents, along the underside of the roof sheathing to a continuous ridge ventilator or separate roof jack vents (whirlybird vents are good too)

Natural air ventilation flow in an attic space is always ideal in lieu of a power fan, as to save on electricity. But sometimes the builder that built the house, does not have a great concept of what it takes to natural ventilate an attic. So we homeowners end up with 150 + deg. F. attics and asphalt tab shingles curling up from the hot roof ....

So we are sold the power attic fan. I don't like them personally, as I have seen attic fires started by them caused from locked up and dirty fan motors. ...

Also, I experienced the last house we bought that sat as a foreclosure, had raccoons living in the attic. They pushed the power attic fan screen aside and went in the attic and set up living quarters for Momma and 4 kids. $250 to get them removed by a pro critter company....

The power attic fan that I just installed had the plastic screen mesh around the housing. I removed it and installed galvanized rabbit cage wire cloth. Critters may push it in, but they will have to have band aids for their nose.

JMO

On edit: Sorry fixin'stuff, for the repeat message... we were typing at the same time.

 

[Gotcha640]

I hooked up some temp sensors to compare each end of the attic just inside and outside the gable vents, and just poking into the living space at the attic stairs, to compare inside attic to outside to inside the house. One fan (don't recall the size) has dropped the outside to attic delta significantly (90 outside 135 attic 82 at attic door with ac at 72, to 120 attic 77 door).

My fan is set at 110, so it's on most of the day during the summer. I give it a couple drops of oil when I do the ac filter.

 

[happymachinist]

The house was built in 1930, so I'm sure the theory on venting has changed a lot since then.

I'm apprehensive in adding a whirly bird with the metal roof as to leaks and such, maybe not a concern, feel free to weigh in on that with your experiences.

Evidence shows me that at one time the vents were static (right term?) At one time and around 2000 the old boy living there at the time added the fan. (he wrote 2000 on the fan motor) I wish we would have been the guy we bought the house from, as the last owner was...... less than knowledgeable. Might have to set up some thermos to do a little testing of my own.

I will also be adding some rabbit hutch screening for prevention of birds, I'm not sure a raccoon could make his way to the vent location but wouldn't put it past those crafty basturds.



Sent from my XT1254 using Tapatalk

 

[CJ7VFR]

Does your house have soffits with soffit vents also? You said you have gable vents. I ask because I can't even begin to tell you how many homes I have seen that have insulation in the attic covering up the soffit vents that totally prevents any air circulation in the attic!! This is really BAD!

When I lived in my townhouse years ago, I was up in the attic one day in the summer and I noticed it was really a lot hotter up there than I thought it should be. My unit was an end unit so I had two gable vents on the one side about 10 feet apart from each other, and there were also soffit vents that ran all along the soffits.

I noticed that I could not see any of the soffit vents from inside the attic, and that they were all covered up by the attic insulation. I crawled over to edge of the attic and pushed down the insulation in the area right above where one soffit vents was.

Holy cow, I could feel the cooler air rushing in thru that one vent! I put a thermometer up in the attic to see exactly how hot it was getting up there, and with all the soffit vents covered by the insulation, and on that 85 degree F sunny summer day, the temperature was closing in on 140 degrees F!

I went to Home Depot and bought a bunch of Raft-R-Mates, which are made to push the insulation away from the soffit vent area, and allow air to circulate up from the soffit vents between the rafters in the roof.

It took me about a day to put them in, and just in the short time I was in the attic, I could feel the difference right away.

The next afternoon, which was another 85 degree F sunny summer day, the thermometer in the attic read 102 degrees F! Almost 40 degrees cooler!

I also ended up putting a gable exhaust fan in one of the gable vents, and blocked off the other one that was next to it so that the fan would draw the air from the now freed up soffit vents instead of the gable vent right next to it. I set the thermostat on the exhaust fan to 95 degrees F and that helped keep the attic at a nice even temperature.

So if you have soffit vents in your attic, make sure the insulation up there is NOT covering them up!!

Jim

 

[happymachinist]

No soffit vents, may add them in the future.

I've set the fan to 110, and I've only caught it running once, it's been pretty breezy so that attic has been venting pretty well without the fans assistance.

Sent from my XT1254 using Tapatalk

 

[MagKarl]

I put one in the attic at my old house and it made a huge difference in summer comfort, well worth it in my opinion. I think I had it set to a little over 100 if I remember right.

 

[Lassen Forge]

We set ours at 120, but then dropped it to 110. ended up saving $$ as the AC wouldn't need to kick on as often to keep the house cool.