Hot upstairs bedrooms - bathroom fan to attic?

12 Replies

Hey BP! 

I recently moved into my first house hack that I gutted and finished up to move-in with my old roommates.  They've complained about the upstairs bedrooms being hot and minimal air flow.  I currently have a storm window with no screens on the old wood sash windows.  Could I install a bathroom vent fan in the ceiling of the upstairs bedrooms to create air flow from downstairs to keep it cool?  I would think this would work? 

I have good attic access above the bedrooms. Since it won't be in the bedroom dealing with moisture - would I need to vent it outside or would venting it to the attic space or right underneath the roof vent be sufficient?


@Andrew Schrader I dont think a bathroom fan moves enough air to make a difference. Before doing that, how is the insulation above the bedrooms? I used to have a tri-level split house and the 3rd level was always 15 degrees hotter than the other levels. My HVAC guy recommended adding insulation and an attic fan to cool the attic space. After doing that, the temp was within 5 degrees.

@Jason D. The upstairs bedrooms are in an A frame style.  The ceilings and upper half of the walls are the roof.  The bottom half of the side walls go into the attic space, if I remember correctly they're un-insulated?  Blown in cellulose insulation in the attic space above main floor.  I don't know what type of insulation is currently in the A-frame rafters. The home is in Montana which sees cold temps and up to 100 F in summer. The roof has a ridge vent on the A-frame but no soffit vents.

I also have a tri-level house in Florida. The upstairs 3 bedrooms were always hotter. I had extra insulation blown in and gable vents installed (there were none before) and that seemed to help a little. I also closed the vents downstairs about 2/3 so the air is diverted upstairs. The A/C unit is closest to the main (first level) so that gets the flow first. The upstairs bedrooms are at the end of the line. 

Try closing the downstairs vents and see if that helps at all. Also, heavy window coverings may help keep some of the heat out. If you have good attic access and can put up a radiant barrier easily (I have a super low pitch roof so this was near impossible), that is also probably cheaper than insulation.

Attic fans work well in perfectly sealed houses. I actually bought a Remington attic fan to install, but ended up returning it before installation. My house was built in 1960, so it is very, very likely that the attic isn't properly sealed from the floor below. If an attic fan is installed in an attic that isn't properly sealed, it will actually pull the conditioned air from the floor below into the attic. So you will be essentially being paying more on your energy bill to cool your attic. You can seal your attic, but for me this was too labor intensive and not easy given the low pitch of the roof.

To my knowledge a ridge vent is almost useless if there are no soffit vents. The soffit vents pull the cooler air in from outside and push the hot air out the ridge vent. I believe in colder weather, you are at risk for ice damming if you have no soffit vents, but not sure.

Anyway, that's just from my research a few years ago trying to cool my attic. Hope it helps!

@Andrew Schrader That seems like an awful lot of work to try and improve air flow. You would be wasting a lot of money to get them installed, not to mentioned the wasted electricity with them on.

I would just throw in a couple fans or window AC units. A fan with the "exhaust setting". 

Thanks, yeah my roommates say they wake up sweating at night with the house heat set to 60F, and it being 40 F outside..?  I don't plan to put in A/C in Montana when it's snowing out... 

Right now the wood double hung windows have 2 glass window sets/ exterior storm windows.  I think I'll just try to buy/ build some screen exterior storm windows to give to my upstairs

A bathroom fan is probably going to produce very little, if any results at all, and it is never a good idea to vent anything into your attic -dry or otherwise. 

The best move would be to hire an HVAC contractor to come look at the structure and flow of the entire house.  There are things you can do to create some circulation without installing central air.  When you need to cool even a small bedroom room, you need to move a whole lot more CFM than what a bathroom fan will ever do.  

@Andrew Schrader So its freezing outside and the guys upstairs are sweltering? Close the upstairs dampers? Insulate downstairs? Are you cold downstairs? Does an exterior door let cold air in next to the thermostat?

@marian smith I'm comfortable/ cool downstairs... my roommate says it gets hot because there's no airflow with only one vent up there. Not sure if they're just grasping at straws. I'm just going to give them a screen on the window vs. Current glass storm window. I don't need to go overboard on this and install an attic fan, etc.