[n0c7]

I have a bathroom fan in the basement that has a 3ft horizontal run from the vent opening to the fan opening. The outside vent has a spring damper that closes tightly and the damper in the fan housing is functioning properly as well but isn't a great seal.

The ducting is a Class 1 insulated air connector and is foil taped at both ends and also has worm clamps.

I do get a slight draft coming through this fan on cold days. Any ideas why and what I can do to improve it?

 

[yuri]

R U sure the outside damper is closing tightly. I have the same issue and we have the same climate. Moisture always gets on the face of it when it runs and it can never seal 100% because of that turning into ice. You have a negative air pressure in the house and most houses do because of natural convections currents etc etc. Not much you can do about it and a bit of fresh air leaking in is not that bad as we need some fresh air anyway. Just the way it is in the Great White North.:yes:

 

[ahrens]

R U sure the outside damper is closing tightly. I have the same issue and we have the same climate. Moisture always gets on the face of it when it runs and it can never seal 100% because of that turning into ice. You have a negative air pressure in the house and most houses do because of natural convections currents etc etc. Not much you can do about it and a bit of fresh air leaking in is not that bad as we need some fresh air anyway. Just the way it is in the Great White North.:yes:

I was going to post pretty much the exact same thing.:thumbup:

 

[djlandkpl]

You could try one of these.

http://www.tamtech.com/store/backdraft-dampers-weatherization-energy-saving,category.asp

 

[n0c7]

R U sure the outside damper is closing tightly. I have the same issue and we have the same climate. Moisture always gets on the face of it when it runs and it can never seal 100% because of that turning into ice. You have a negative air pressure in the house and most houses do because of natural convections currents etc etc. Not much you can do about it and a bit of fresh air leaking in is not that bad as we need some fresh air anyway. Just the way it is in the Great White North.:yes:

Went outside to verify and it's surprisingly tightly sealed. We're not venting moisture as it's a home salon and the fan is being used to expel fumes from chemical processing and not a bathroom with humidity.

The only thing that has me stumped is why the other fans on the upper levels are not cold at all yet the basement one is. Only difference I can really see is that it's a very short horizontal run, low to the ground.

 

[n0c7]

You could try one of these.

http://www.tamtech.com/store/backdraft-dampers-weatherization-energy-saving,category.asp

I actually found that googling earlier. Any idea if they actually work?

 

[djlandkpl]

I actually found that googling earlier. Any idea if they actually work?

They work. I have two of them. They are a a bit pricey but I like them because they add very little resistance when the fan is running. They seem to block outside air well. My fans don't have any terminations on the outside as they go to ports in my soffits. I originally had flap dampers and I could hear them slapping closed on windy days. These stop the noise and the air.

 

[yuri]

3 ft is short and if there is no air moving backwards out the vent ( blow cigarette smoke at it ) then what you are getting is simple conduction of cold air. If it was more than 3 feet long then the dead air in there would warm up, worse because the pipe is well insulated, so it is just cold air and conduction. Like walking up to a 2 pane older window you can feel the cold from 3 ft away thru the air. I have low E argon 3 panes and you cannot feel any cold at all by them/amazing windows. Technically it is a lack of conduction as heat flows from hot to cold but the lack of movement in the pipe is the reason. You get my drift though.