How much is your bath vent fan costing you in heat?

Ryland · 09-26-11, 11:48 AM

How much is your bath fan costing you in heat? I was thinking about this because over the summer we found that the window A/C was better then running a dehumidifier because it's dumping the heat outside to dry the air inside the house out, but in the winter you want to keep as much heat inside the house as you can, so why not, instead of pushing that warm moist air out of the house in the winter, dry it out at that point with a dehumidifier?
Average bath vent fan is 80 cubic feet per minute of venting and I would guess it stays on for 30 minutes at a time and the fans are cheap to run, 40 watts for most old ones and down to 20 watts for an energy star rated fan, but an 80cfm fan left on for 30 minutes is going to pull 2400 cubic feet of heated air out of the house in the winter, air that then is being replaced by fresh cold air from outside the house that is coming in from drafts and cracks in the house.

So my question boils down to, how much does it cost to heat 2,400 cubic feet of air? and is it cheaper then running a 600 watt dehumidifier for what I suspect is going to be about half an hour as well, just judging from using the dehumidifier to dry out my living room in the summer from 90% down to 60%.

09-26-11, 11:48 AM	#1
Ryland Master EcoRenovator Join Date: Mar 2009 Location: Western Wisconsin. Posts: 913 Thanks: 127 Thanked 82 Times in 71 Posts	How much is your bath vent fan costing you in heat? How much is your bath fan costing you in heat? I was thinking about this because over the summer we found that the window A/C was better then running a dehumidifier because it's dumping the heat outside to dry the air inside the house out, but in the winter you want to keep as much heat inside the house as you can, so why not, instead of pushing that warm moist air out of the house in the winter, dry it out at that point with a dehumidifier? Average bath vent fan is 80 cubic feet per minute of venting and I would guess it stays on for 30 minutes at a time and the fans are cheap to run, 40 watts for most old ones and down to 20 watts for an energy star rated fan, but an 80cfm fan left on for 30 minutes is going to pull 2400 cubic feet of heated air out of the house in the winter, air that then is being replaced by fresh cold air from outside the house that is coming in from drafts and cracks in the house. So my question boils down to, how much does it cost to heat 2,400 cubic feet of air? and is it cheaper then running a 600 watt dehumidifier for what I suspect is going to be about half an hour as well, just judging from using the dehumidifier to dry out my living room in the summer from 90% down to 60%.