My master bathroom did not previously have bathroom fan, but I installed one and have had wonderful results with keeping the steam from building up and exhausting the moist air. I am using both a fan and a roof vent that have pretty weak metal flaps to reduce the cold air from making its way into the house. I can hear the flap on the roof vent at times during very windy conditions, but not often.

I have taken showers without turning the fan on and the warm, moist air finds its way out of the vent very easily. It is amazing how much just having the air path in place helps the exhausting compared to when a fan was not present. This does concern me though, as I wonder, if air can leave the bathroom that easily with the fan off, could I be losing heated air when the fan isn't turned on? I plan on insulating the pipe that is in the attic now, though I am not sure if this would affect the rising of the warm air/dropping of the cold air.

Any thought or opinions? Do I need to be concerned about this?

2 Answers 2


You probably want to install some kind of a damper or louvers that will minimize air exchange through the vent when the fan is shut off, right? I would expect that the fan assembly itself might have a damper built into it, but maybe the housing is binding the damper. Or maybe it doesn't have one.



  • If the fan doesn't have a damper it is easy enough to add one to the vent line. Between the louvers on the exterior and the baffle it will reduce the amount of heat loss and exterior air penetration inside the house. Note, when ever the pressure inside the house is greater than outside (warming up cold air will do this) any and all vents will exhaust this. You can't stop this and just have to live with it, anyways it will find itself outside through any cracks/seams it can even if you don't have vents.
    – diceless
    Commented Nov 23, 2014 at 4:51

The fan should have a damper, as should the vent. If you insulate the pipe in between, that should go a long way in helping things.

It won't be air tight, of course. It is a hole in your ceiling, after all. But it should help.

Keep in mind that you're sucking way more heat out when the fan is on than is likely escaping the entire rest of the day.

With an unlimited budget, you could install a heat exchanger on the vent pipe. But the ROI on that may never be realized.

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