# What is the proper vent cap for bath/kitchen fans



## Roofmaster417 (Jun 9, 2010)

Could you safely take a picture of the vent that is being used?,,,,then post the picture?


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## Roofmaster417 (Jun 9, 2010)

Roofmaster417 said:


> Could you safely take a picture of the vent that is being used?,,,,then post the picture?


From your description of the vent,,,,,it sound like a regular vent for attic ventilation was being used rather than a baffled damper vent.


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## bcdemon (Jul 12, 2010)

You want a "bathroom flapper vent". It has a flap inside that keeps cold air from getting in. Right now with just a roof vent covering your bath fan hose, cold air can run down that hose when the fan is off. So if you have a shower, and the hose fills with steam/moisture, what do you think will happen when the fan is turned off and cold air enters the hose?


If you have an accordion type fan hose:
Also, try and make sure your hose is as straight as possible from the fan to the flapper vent, just to prevent any moisture sitting in the ribs of the accordion hose. 

This page shows a good diagram of a flapper vent


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## michega (May 19, 2011)

I can't get on the roof at this time because of snow and ice etc. I did find some pictures on the internet that best resembles the vent cap I have. The one they installed does have a damper on it as does my bath fan housing. Is this the proper vent cap for a bath fan? I don't know. I do know that the one now is basically venting the warm moist air our the opening around the bottom outside edge of the vent can which is only about 3/4" (just enough to slid you fingers under) off the roof deck/shingles. The moisture and melted snow from around the vent is running down to my gutter (about 3' away), and is now going over the gutter and creating icicles. We've only had snow for a week and this is happening already. Will this not create an ice dam as the winter continues causing the water to be forced under the singles creating further problems? I assumed the vent cap should be a "goose neck" or "chimney" style where the vent opening is 8-12" above the roof deck/shingles. What are your thoughts? How do I find out what is the correct style, or is what I have now correct?


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## michega (May 19, 2011)

Thanks bcdemon. There are two parts to the vent cap. The first is the part that the hose attached to, much like the adapter collar part in the link you sent. It is installed 'into' the roof deck. The second part attaches to the first and would be like the brown is to the black on the link you send. I do like the duel flapper idea although it seems the air would be once again forced directly, although not nearly as much, onto the roof deck. Do you use this style? Do you have problems with freeze up in winter?

Here is a link of the style I assumed would be used:
http://www.primex.ca/large_products/construction/HVAC_outdoor/RV28.htm
or the smaller version:
http://www.primex.ca/large_products/construction/HVAC_outdoor/RV20.htm

Thoughts?
Feedback?


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## michega (May 19, 2011)

RoofMaster, I've managed to get some pictures of the vent. Thanks for taking a look and for your input.


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## bcdemon (Jul 12, 2010)

michega said:


> Thanks bcdemon. There are two parts to the vent cap. The first is the part that the hose attached to, much like the adapter collar part in the link you sent. It is installed 'into' the roof deck. The second part attaches to the first and would be like the brown is to the black on the link you send. I do like the duel flapper idea although it seems the air would be once again forced directly, although not nearly as much, onto the roof deck. Do you use this style? Do you have problems with freeze up in winter?
> 
> 
> or the smaller version:
> ...


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## matthew5 (Nov 19, 2011)

I am in Calgary and my roofer installed the same vents for my bathroom exhaust. It is essentially an attic vent with with and insert that snaps in the bottom with flapper. I have found it to be quieter (I used to hear noises from outside through the vent) than the other type on my roof but since the temperature has dropped below zero, the flap has frozen shut and running the fan does not thaw it out when it is colder than about -2 deg.C because there is no air movement. I only found this out after going into the attic and discovering that the roofers had not properly re-attached the duct to the vent cap. With the flapper froze shut, the bathroom vent was venting into the attic. I am curious if you have the same problem with a frozen flapper. I think this type of cap is more prone to ice build up inside because the air has to work its way up and out of the vent cap instead of being directly blown out like the traditional design.

I plan to give my roofer a call and complain about the vent cap but maybe all vent caps with flappers have the problem of freezing up?

I don't know if you will find one that does not melt the snow on your roof. Most I have seen are low profile.

If you want to know why it is important to make sure the duct work is sealed properly to the fan and vent cap read here is my experience from last year. 

The old vent cap had a fairly heavy flapper and although the duct was loosely connected to the cap, the resistance from the flapper (maybe it was frozen too) allowed the air to go into the attic instead of out the vent cap. (The previous home owner had replaced the caps shortly before I purchased the home, and the installers apparently did a poor job). You will know if your house is leaking moist air into the attic if the tips of the shingle nails poking into the attic attic have ice balls (not icicles) attachd to them. Consequently, I had a big mess in the spring when it all melted and had to replace the ceiling in my bathroom and some other places in the house. This is why I checked to see if the roofers had properly re-attached the ductwork, and guess what.. they had not. I would have had the same problem this winter.


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## Wildbill7145 (Sep 26, 2014)

Just out of curiousity, I've got exactly the same vent setup as the pictures in post #7 of this thread. The problem I've having is the thing gets completely buried in snow during the winter as we live in what's called the 'snow belt'.

Once it's buried and the fan is used, it melts the snow on and around it but it's so cold it refreezes and creates a damn all around the thing. I've had to get up on the roof, dig it out (gently) and use a hammer to knock the ice from around it off (again, gently so as not to damage the shingles).

Is there a way to dismantle that type of vent and add pipe to it to make it say 1' taller? I really don't want to get into replacing the whole thing as I've been told that gets into fiddling with shingles, etc. and I've had horrible luck with that in the past.


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## lenaitch (Feb 10, 2014)

We also live in a high snow load area - we can get 2-3' accumulation in some years (even our 'turbine' vents get covered). A friend of mine had his roof re-done a couple of years ago and thought he was being smart by having a "gooseneck" type vent to keep it above the snow but it continually froze above the roofline. i don't know for certain if it was just ABS piping and if there is such a thing as an insulated double-wall 'high lift' type of vent out there, but I feel your pain.


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