# High Efficiency Furnace Exhaust Vent-Need Bird/Insect Screen



## B4Dark

I just had a high efficiency Lennox furnace installed and both the through-wall exhaust and air intake pipe are open at the end ie. no bird or insect screen. Can some sort of a screen be added or will this screw up the furnace operation? Any suggestions on how to keep the critters out of the pipes would be appreciated.


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## beenthere

A screen in the exhaust causes lots of no heat causes, when it freezes over.


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## yuri

A screen will freeze up and plug up with spider webs. These are good for scaring away the birds.


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## gena

Try to use street 45 on the exhaust; intake should have 90 on it, no glue, pull it out when below 30F.


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## B4Dark

Do you think a cage similar to what is used on the end of a suction pump intake hose if the mesh was 1/4 or 1/2 inch would work without freezing up? Also, is the intake as critical say 1/4 inch mesh?


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## TJ_in_IL

Because the furnace is a High Efficiency, or condensing unit, there is a high moisture content on your exhaust. In the winter, during extreme cold, this condensate will freeze on the screening, and clog the screen. 
What I did was put a 45 elbow on the output, but not glued. As soon as I was done heating for the season, I removed the 45, and installed a cap. I have a reminder warning on my system (label on thermostat and sign on the winter/summer humidifier baffle) to remove the cap when the heating season starts. If I forget, the backpressure will trip a code, and not fire the unit.
Without the cap I get bees building a nest. Not fun.


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## yuri

Which Lennox unit did you have installed? I am a Lennox tech. You cannot obstruct or change the end of the exhaust pipe as it has a special fitting called an accelerator. If you alter the piping it will cause pressure tripping problems.


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## Marty S.

Yep has to be straight out on a Lennox exhaust. Cover it after heating season and remove before firing up the furnace if it makes you feel better. Critters are not really an issue though


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## B4Dark

I installed a Lennox G61MPV-60c-111 natural gas 95% efficiency furnace at elevation 7,400 feet in Colorado. I was thinking about adding a 12 inch diameter by 8 inch long basket of 1/2 inch wire mesh clamped around the end of the 2-3/8 inch PVC horizontal exhaust vent and also covering the 4 inch PVC air intake opening with the same mesh. This would keep out the birds and but not the bees. I don't think the 1/2 inch mesh would ever ice up or restrict the exhaust vent? The reason for wanting to leave the vents open is to circulate air with just the fan during the summer months. What do you think?


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## yuri

*"The reason for wanting to leave the vents open is to circulate air with just the fan during the summer months. "*

Which vents do you mean? The PVC venting is only for the burner and not house ventilation. That is the larger size of venting and I actually had a bird fly in the exhaust of one and get as far as the ventor fan so it is possible. As long as you do not add to or alter the PVC pipes with elbows etc you should be okay. Mesh may be ugly but it will work if it just surrounds them. You do need to check them once a week and when it is snowing for any buildup or icing or hoar frost. That furnace is not overly finicky about venting and pressure switch tripping but you want to avoid it.


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## kb3ca

I bought some of that soft aluminum gutter guard from HD that you put over gutters to keep leaves out. The holes are large enough for air flow but small enough to keep critters and leaves out. I form fitted a piece over the intake and the exhaust pipes and have never had a problem. I am using 4 inch pvc with a run of about 15 feet. Been working just fine for years.


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## B4Dark

Sorry I was not clear about the vent reference. You are right, the furnace intake and exhaust PVC vents have nothing to do with circulating the air with the furnace fan. I must have had a brain fa..t ! Anyway, thanks everyone for helping me and I am going forward with either 1/2 inch hardware cloth (mesh) or the suggested HD gutter leaf guard material to keep out the birds and leaves next fall. Meanwhile, I am going to cap both PVC pipes till then.


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## DanCB

I put vent caps on my open PVC pipes. I have several trees which litter my roof with sticks and leaves (see http://www.fitthewondercap.com/). They were around $10 a piece and took a second to install.


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## beenthere

DanCB said:


> I put vent caps on my open PVC pipes. I have several trees which litter my roof with sticks and leaves (see http://www.fitthewondercap.com/). They were around $10 a piece and took a second to install.



Looks like advertising.

They are also a code violation in many areas. When installed on the exhaust pipe.

I can see many no heat problems if its installed on the exhaust.


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## DanCB

I have had zero problems with it installed on my exhaust pipe. Also, the cap is CSA certified. 

beenthere - I guess I should contact the site owner to see if I can get paid for my 'advertising'. lol


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## beenthere

DanCB said:


> I have had zero problems with it installed on my exhaust pipe. Also, the cap is CSA certified.
> 
> beenthere - I guess I should contact the site owner to see if I can get paid for my 'advertising'. lol


CSA approved. That ain't hard to do. Do you know what it means?

How long have you had that thing on your furnaces exhaust?


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## RL Bolen

:no: Answers dont help me either. Wasps are making nests in the pipes and when I change my filters they don't want me around. Wasp nests also constrict the air flow in the pipes and I cannot get to them to remove.


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## scottmcd9999

What filters are you referring to? This thread had to do with venting high efficiency furnaces, and that wouldn't have anything to do with your filters.


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## 2big2fail

*screen*

I just had an high efficiency furnace installed. I found this thread because I was wondering about birds and insects getting into my intake and return vents. It seems to me that when your heating season is over you could put fiberglass screen over the ends of the pipes and secure them with cable ties until its time to fire up your system in the fall. Just remember to take these off before you start heating again in the fall. Problem solved for a few cents.


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## yragsapo

beenthere said:


> A screen in the exhaust causes lots of no heat causes, when it freezes over.


True. I just had that problem last night. The contractor had used zip ties to put whatever he had available (apparently) over the 2 openings in my through-wall PVC pipes. One screen was a very wide plastic mesh, which is fine. Unfortunately, he used a fine screen, like for a screen door, on the intake, which froze over in the snow storm last night, causing my downstairs furnace to turn off. When I pulled the screen off this morning, the furnace worked fine. Having a screen is fine, if the openings are about 1/2". That will keep the leaves and animals out, which is the main goal here.


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## jeepgrady

I have had problems with stink bugs getting in the furnace through the cold air intake. Since my vent goes through my roof I was think about putting a screen over the intake pipe where it enters the furnace. Would this be acceptable?


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## yuri

No, it may reduce the airflow and start tripping the pressure switch or won't burn properly or fire up properly which can be dangerous.


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