# Hornets in the HVAC?



## dj3 (Apr 27, 2020)

A gas furnace will have a vent through the roof. The vent should have a cap, and if you see hornets, you will have to treat them.
2-3 hornets a day may be just looking for a place to build a nest. Treat them early to get rid of them.
Do you have a chimney? make sure the hornets are not there.


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## DexterII (Jul 14, 2010)

Like dj said, it's that time of year when they're nesting, and they'll get more aggressive once they start to settle in, so you want to keep them out. You mentioned suspect areas, so you obviously have some places to start. For larger gaps or voids, you might want to start with spray foam or stuff some insulation in then seal them as needed. For smaller holes or gaps, caulk is the most common cure, but I like duct seal, which you can buy at your local hardware or big box, about the size of a block of cheese, slice off what you need, roll it in your hands for a few seconds, and mold it into place.


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## LS-6 (Nov 26, 2019)

Are you seeing the hornets inside your house? :surprise:


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## mi2k (Apr 2, 2020)

Thanks for the replies folks.

We are seeing the hornets in a less used area of the house that does not get much traffic, does not have doors to the outside or open windows close by. We have seen the hornets on the ceiling vents a few times which is why we suspect they may be getting in from there.

The AC is not coupled with a furnace. Our heat is boiler+baseboard. So what kind of vents may be connecting to the air handler/ducts. I will look, but the air handler is in the attic. I am somewhat wary of getting in there and stir a hornet's nest.


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## Daneal (Jun 15, 2020)

LS-6 said:


> Are you seeing the hornets inside your house? :surprise:


:biggrin2::vs_mad::vs_mad::vs_mad:


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## DexterII (Jul 14, 2010)

So you have multiple small vents in the ceiling throughout the house that conditioned air blows out and one large return? And a condenser outside the house?


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## DoomsDave (Dec 6, 2018)

@mik2, welcome and nice to meet you!

I'm in California now, but used to live in Ohio, which, like MD has hornets, yellow jackets, etc.

If you can, please send a picture of the critters. I say this because sometimes "hornet" is a catchall term that has been applied to wasps that aren't. That can be important; some wasps that look nasty, like mud daubers, etc., aren't nearly as nasty as hornets can be.

Hornets, and their cousins the yellow jackets are NASTY when their nests are disturbed. As Toby Keith might say, "I wish I didn't know now what I didn't know then" about how nasty. 

They make paper nests, with a queen, and the colonies in the northern U.S. last one summer season, before disbanding in the fall. The workers wander off and die, while the new queens hide over winter and start new colonies in the spring.

In late July, I'd say the colonies are well along, and no longer looking but being there. 

If you're finding them in your house, I'll bet they're inside somewhere. I'd look all around the outside, focusing in particular in the sections outside the rooms where you're finding them. Another reason for a picture is to get a better idea where to look for a nest. Yellow jackets nest in cavities, at or near the ground; hornets nest higher up, usually. 

Below are pictures of bald faced hornets, and a nest. When I was a kid, my friends and I used to call occupied hornet nests "Masochist's Football."


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## mi2k (Apr 2, 2020)

DexterII said:


> So you have multiple small vents in the ceiling throughout the house that conditioned air blows out and one large return? And a condenser outside the house?


Yes, that's correct. But we have seen the hornets in only one area.


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## DoomsDave (Dec 6, 2018)

Below is a pic of a yellow jacket, which is usually a bit bigger than a hornet.


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## mi2k (Apr 2, 2020)

Thank you, Dave. Here are some pictures:
https://photos.app.goo.gl/ezLaDxYWxLKAEqHKA

Are these European Hornets?


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## DexterII (Jul 14, 2010)

Okay, that's what I figured, but wanted to make sure what you had going on there since you asked about the AC system. The AC and the roof ventilation are two totally separate systems, no connection whatsoever, so barring a hole in the duct work, which is very unlikely, there is no way for them to get into the AC system via the roof vents. In simple terms, you can think of the relevant part of your AC system as a loop, taking air in through the large opening, conditioning it, and redistributing through the small vents, no intervention with the attic nor the outdoors, other than equipment placement obviously. Now, if those small vents are not installed properly, and there are gaps around the outside of the vents, yes, that gap would lead right into your attic. Your condenser though is outside, and while no ductwork goes to it there is a lineset that runs from it to the house, maybe into the basement or crawlspace, or maybe up the side of the house and into the attic, and that lineset is what I was referring to earlier when I mentioned caulk or duct seal. I think you said that you don't want to go up there, but it's your house and you should inspect the attic from time to time anyway, so go up there and you should be able to see the bottoms of the vents and make sure the screens are intact. Just be mindful of the hornets, and as long as you don't go poking at them you'll be fine. But you do need to see what's going on there once in a while anyway, and particularly now with the hornets getting in.


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## mi2k (Apr 2, 2020)

DexterII said:


> Okay, that's what I figured, but wanted to make sure what you had going on there since you asked about the AC system.


Thanks again. I am going to check in the early morning hours.

I see a few HVAC diagrams that have an outside air intake in to the air handler, but based on what you are saying I guess they are not common. For example https://www.nachi.org/images2012/Article Images/Figure_1_ProperInstallationFilter.png


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## DexterII (Jul 14, 2010)

Yup, mornings or evenings are the best times.


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## mi2k (Apr 2, 2020)

Yesterday evening I covered the two ceiling vents with cloth mesh so that the hornets cannot come in without cutting the mesh. Today we found couple of hornets sitting on the mesh IN the room. This proves that they are not coming in from the AC vents -- they probably just like to hang around the vent. I must now locate their real entry point.


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## DoomsDave (Dec 6, 2018)

mi2k said:


> Thank you, Dave. Here are some pictures:
> https://photos.app.goo.gl/ezLaDxYWxLKAEqHKA
> 
> Are these European Hornets?


 @*mi2k* , those don't look like hornets, which is nice to know. The huge problem with hornets or "yellow-de-jackets" is that they have large colonies; the wasps pictured look more like mud daubers. I wouldn't stuff them down someone's shirt as a prank, but they're not the "killer bees" that hornets and YJs can be.

I once had them build a nest inside my house, tubes of mud they stuffed with paralyzed spiders, then sealed off till the new wasps emerged. When that happened, scrape-scrape scrape and repaint.

Do the wasps get aggressive if you mess with them? Do they kind of go back-and-forth in flight before they land?

I'd keep an eye on openings around your house at either dusk or dawn; that's when they come home or leave for the day, which might provide a clue where they are. 

I'm RELIEVED to know they're not actual hornets.


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## DexterII (Jul 14, 2010)

There you go. What you did to check it and what you learned both make sense. I would have bet that the AC ducts were not your problem, but now you know. So I would keep looking for any possible entry points, particularly in the foundation, soffits, and wherever any telephone, cable, gas, water, or other lines enter the home. Meanwhile, if you can, I would probably try closing that room off tomorrow and see if any more show up. They might be coming directly into that room or they might be ending up there because of the amount of sunlight or whatever.


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## mi2k (Apr 2, 2020)

Dave & Dexter, thanks for your help!



> Do the wasps get aggressive if you mess with them? Do they kind of go back-and-forth in flight before they land?


We have successfully used a towel to swat them. Most of the time they are lethargic, but when they are not, they fly around bumping into the ceiling and try to settle on ac vents, recessed lights, or side walls.



> The huge problem with hornets or "yellow-de-jackets" is that they have large colonies; the wasps pictured look more like mud daubers.


After having seen many wasp pictures, I think they are paper wasps -- not aggressive, but not harmless either.



> So I would keep looking for any possible entry points, particularly in the foundation, soffits, and wherever any telephone, cable, gas, water, or other lines enter the home. Meanwhile, if you can, I would probably try closing that room off tomorrow and see if any more show up. They might be coming directly into that room or they might be ending up there because of the amount of sunlight or whatever.


The wasps are showing up only in our "in-laws apartment" which is already secluded from the rest of the house. I think they are entering directly in this area rather than coming from elsewhere in the house. There is an unused kitchen there with an exhaust vent over the range. They may be entering through a gap along the rectangular duct. The ceiling has recessed lights -- those pockets have access from the attic, and the attic is connected to the outside through soffits.


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## DexterII (Jul 14, 2010)

> There is an unused kitchen there with an exhaust vent over the range.



Yup, you nailed it. Look up into it from outside and you'll probably find the door is the culprit. Be careful though because with that in the mix it's a likely spot for them to already have an established nest, easy in and easy out, well protected, and the ones you're seeing inside the house are scavenging for whatever they can find to take back home with them.


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## Missouri Bound (Apr 9, 2011)

mi2k said:


> . This proves that they are not coming in from the AC vents -- they probably just like to hang around the vent. I must now locate their real entry point.


Not really. It only suggests that they may be trying to get back in the vent and you blocked it. Why else would they be there?


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