I’m a fairly new Sense user (little over a month in) and 8ve found it very useful to see what is consuming so much electricity.
Ive recently discovered that it seems my attic fan is runing indefinitely. Sense hasn’t discovered it, but that’s likely because it’s always on. It draws about 230w. It has a temp and humidity sensor, and I tried adjusting the humidity sensor, but I need to raise it to almost 70% to get it to shut off. It’s the middle of winter in NJ and we struggle to keep the relative humidity at 40% in the winter inside the house. I know attics can be different, but perhaps this switch is faulty? Or just inaccurate?
I wish there was a point inline sensor I could add to some devices. I’ve added several TPLink plugs and power strips that sync with Sense…
Thoughts? At 230w, it’s definitely adding to the power bill significantly, running 24x7. I do have Sense to thank for helping me track this down.
You’re talking about a true attic fan that is just drawing air through the roof space or is it a whole-house fan that is pulling fresh air into the conditioned space? I assume the former.
In that case my limited understanding is that there’s a tricky correlation between RH and temp … in winter you probably only want the fan on when the internal RH is high AND the temp is over a certain minimum AND the outside RH is lower. Dew point!
Without going deep, my thought would be to switch it off for now and give yourself enough time to come up with a Sense-driven smart control by summer!
I’m guessing others will weigh in with some practical options in that regard.
Attic fan efficacy is a hotly debated topic in the field of home energy performance, so get ready to hear some conflicting opinions!
Humidity control using an attic fan in New Jersey is, IMO, a futile endeavor. The “correct” humidity level for the attic is equal to the outdoor humidity, so setting a fixed value will have no purpose other than to waste energy. So, I’d set that to the max so that only the temperature control is active.
Now, as to whether the attic fan should be there in the first place: if you have good passive venting (clear soffit vents combined with a ridge vent and/or gable vents), I’m of the opinion that a fan is not needed. If you have poor passive venting, then the fan may be a good tool to get by until the next time the roof is replaced and venting can be added. Also, make sure that you don’t have any exhaust fans from within the house venting directly into the attic.
I’ve experienced your exact situation, regarding my Attic Fan - here in the Northeast Ohio area! I elected to sever the original single inline power source.
An electrician installed an outlet, leading from the power source
Affixed a plug on the line, leading to the Attic Fan
Leveraged a Smart Plug into the newly installed outlet
Inserted the new plug into the Smart Plug
This action afforded me complete automated control of the Attic Fan. This low-cost effort gave me a significant reduction in my “Always On” value and monthly energy consumption - not to mention ensuring a mold-free attic area!,
Thank you all for your advice. Yes, I’ve read some debate on the usefulness of attic fans. I find it’s number one usage is quickly pulling hot air from the house when cooling in the summer.
I am keen on the idea of putting a plug on the end so I can use a smart power switch. I think for the time I’ll set the humidity control all the way up and do some additional research.
I would also put some temp/humidity sensors in the roof space and try to quantify things.
A constant-on fan at 200W is probably costing around $20+/month.
Any roof work is going to cost significant time and/or $.
Investment in some good sensors will save you grief and money in the near term.
This would be my “fancy” pick for reading temp & humidity, if only because I’ve used them in a commercial building management setting, but there are plenty of cheaper options: Wireless Humidity and Temperature Monitoring Sensors
That said, as @pswired hints at: you could just switch off the fan, at least until summer … and stick your head in the roof space periodically and see/sniff how it looks and feels.
-They use a lot of power
-They become a fire hazard when the motor reaches end of life and seizes up
-If there isn’t sufficient ventilation in the attic to provide makeup air, they will depressurize the attic and draw out conditioned air from the living space, increasing the HVAC system load
I’ve been thinking of adding an attic fan to my rooftop, but will monitor this thread… Sounds like the benefit of an attic fan is a little controversial, and I would love to understand the various opinions…
I have excellent attic insulation, but like any insulation, it absorbs the heat and keeps it away from the living space…but only for short durations… If we have a multiple day heatwave, the insulation eventually is fully absorbed in heat and the living space starts to get hot because now we have a big hot blanket on top of us!!!
We currently have “brow vents” in the top part of our pitched rooftop, and my original roofer said that this was all I needed… I was going to add an attic fan near the top pitch of the roof, but I was told that if I don’t cover the “brow vents” that the fan will actually cause a
“short cycle” of air (i.e., the attic fan would suck air from a nearby “brow vent” and push it right back out to the exterior, which minimizes the benefit of having the attic fan in the first place)…
I’ll be in the background monitoring the conversation here! Very interested in the discussion…
There’s lots of debate on the merits of an attic fan. Ultimately, I use mine to unload hot air in the summer when it gets overly sweltering - and it has the added benefit of creating an upward draft when trying to cool the house down when we turn it on (and it’s already hot in the house). More importantly is winter use - using the fan keeps cool dry air flowing in the attic. In the winter, humidity levels rise in the attic due to the warmer air below (and increased humidity from people, cooking, etc.). The fan will keep air moving and prevent condensation.
I did remedy mine using a smart switch in place of the control box on the fan, and a separate temp/humidity sensor. I then use SmartThings to tell it when to turn on and off. I have two cycles - one for summer and one for winter. The winter one switches the fan on when the temp drops below 32 deg. and humidity rises above 70%, then turns off when humidity drops below 50% or the temp goes above 45 deg. It never runs long, and I have it notify me when it switches on and off so I can monitor it.
The control boxes that come with the fans are horribly inaccurate and mine would run 24/7 unless I jacked the dials all the way up.
Would like to take it one step further… Our roof vent is wind powered. 18 inch or so in diameter. Vertical slots. Looks to be chromed… Seams like it is also spinning. When we had our new roof put on we had it put in. It was a hot summer day and could felt the drop in the radiant heat off the ceiling almost immediately. Don’t need to switch power… Solar or otherwise… Been up there for nearly ten years… My 2 cents… Gerry … Will get you a picture if you want…
