# Covering a furnace outlet duct



## Michael Thomas (Jan 27, 2008)

B-Vent? PVC? Something else?


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## vsf (Oct 20, 2010)

*covering a furnace outlet duct*

The duct is 3" (I think) standard PCV Pipe....I'm just concerned about mice or whatever getting up into pipe & house but probably shouldn't cover the duct opening?

Thanks in advance!


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## fabrk8r (Feb 12, 2010)

That pipe is likely to be the exhaust vent for your furnace. Are there two pipes or just one? Can you follow it back to your furnace to be sure?

If there are two, one is combustion air and one is exhaust. Not recommended to cover with wire mesh due to possibility of freezing in cold temps when furnace is running. I've never had a problem with critters getting into the exhaust vent, but children and golf balls can be a nuisance. Some people cover the vents in warm weather to keep birds and bees out, but it's not a good idea during heating season.


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## vsf (Oct 20, 2010)

*covering a furnace outlet*

Only 1 PVC Pipe and believe it is exhaust. Your comment sounds good and answers my question: will consider putting something over it during summer.
I very much appreciate your help.


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## veesubotee (Nov 22, 2008)

I once had a bird feeder which the squirrels would continually raid (climb up the pole).  Greased the pole. That was the end of that.

V


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## vsf (Oct 20, 2010)

Thank you - that's good advise - for my duct & feeder both!


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## kb3ca (Aug 22, 2008)

I put some of that soft aluminum gutter guard over my 3" PVC exhaust. The holes are small enough to keep the critters out but doesn't obstruct the exhaust flow very much. I got the material from Home Depot. It has been on for more than ten years with no problems. I also drilled a small hole in the bottom of the PVC pipe where it exits the wall so that condensate can drain onto the ground and not accumulate on the inside of the pipe. No icing or any other problems encountered and no critters. Hope this helps.


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## SD515 (Aug 17, 2008)

Do the instruction that came with the furnace mention anything? Some recommend (and even come with) 1/4" mesh screen.


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## vsf (Oct 20, 2010)

*covering a furnace outlet duct*

I will look at the instructions (had not) but the mesh screen was what I had in mind - thanks for the suggestion


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## fabrk8r (Feb 12, 2010)

If you put 1/4" wire mesh into or anywhere close to the end of that vent pipe you will most likely have ice build up when the temperature is below freezing since you have a condensing furnace. Ice build up will cause restriction and the furnace will shut down and not light due to back pressure in the vent until the ice is removed.

Why all the concern about covering the vent pipe? Ask any HVAC tech and they will tell you not to worry unless you have children who like to put things into places they don't belong. Animals are smart enough to stay out of confined places which smell like there is a lack of oxygen present.


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## vsf (Oct 20, 2010)

*cover a furnace duct outlet*

Makes sense - I will quit worrying about mice or anything getting up into duct.
thank you


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## fabrk8r (Feb 12, 2010)

FWIW, it would be virtually impossible for any varmints to enter your duct through the furnace vent pipe because the combustion chamber is separated from the duct, unless you have a hole in your heat exchanger...in which case you have bigger problems than mice!


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## vsf (Oct 20, 2010)

*covering a furance outlet duct*

I feel better about the duct opening situation now & very much appreciate your comments.....as well as another one that suggested drilling a hole at the bottom of vent to allow moisture to drip out. I will now be able to focus on the next thing for me to stress about
Thanks again


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## fabrk8r (Feb 12, 2010)

Don't sweat the petty things...and don't pet the sweaty things. ;o)


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## Bobbiejo (Oct 21, 2021)

fabrk8r said:


> That pipe is likely to be the exhaust vent for your furnace. Are there two pipes or just one? Can you follow it back to your furnace to be sure?
> 
> If there are two, one is combustion air and one is exhaust. Not recommended to cover with wire mesh due to possibility of freezing in cold temps when furnace is running. I've never had a problem with critters getting into the exhaust vent, but children and golf balls can be a nuisance. Some people cover the vents in warm weather to keep birds and bees out, but it's not a good idea during heating season.
> [/QUOTE. My aunt has mice getting in hers it so low to the ground. The pipe was added when she had humidifier added to her furnace . How can she keep them out?


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## supers05 (May 23, 2015)

This is an old thread. In the future, you should make a new one. This may or may not be legal depending on the furnace brand and your location. Rules vary greatly with this. 

The termination can also be moved. It shouldn't be closer then 14" above the snow line. 



https://www.homedepot.ca/product/ipex-homerite-products-3-inches-termination-vent-screen/1000655633


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