Bats and B-vent question

[Lee Batchelor]

Hi all,

We have a Vermont Castings, small gas stove in our kitchen. It is vented vertically through to the roof with about 12 feet of pipe. The pipe is a dual system I think they call a B-vent. The inner exhaust pipe is 4 inches in diameter and the overall diameter is 7 inches. The gap between the inner pipe and outer circumference is about 1 3/8 The weather cap is wide open, that is, it has no screening or mesh. In the summer, I shut off the pilot flame, which I know is wrong! Since doing that, I've had three bats enter the house - one about two months ago and two a few days ago. I was able to successfully catch them and release them back outdoors.

Is it possible they came down the B-vent and escaped the stove body only to become trapped in the house? Will keeping the pilot flame lit prevent further entry?

I built this house and made sure every exit point for wiring and plumbing was sealed with Mono caulking. I recently had all the floor truss pockets professionally sprayed with a 2 lb. foam. I actually had a bat come in years ago - before the spray foam job, so I doubt they're coming in through gaps in the floor truss pockets, since I've sealed them up 100%.

There's surprisingly little information on the net about this. All they talk about is brick chimneys. Thoughts? Many thanks...

- Lee

 

[Corey]

I'd think a bat could certainly get down the flue. Typically what I have seen... bats, birds or whatever... once they start in the flue, they can't effectively fly, so end up tumbling clear to the bottom. So even a brief exploration of the opening tends to trap them and send on a 1-way trip to the bottom.

What would be less clear is how they would get out of the stove. I don't know what specific model you have, but in my stove (assuming the front door isn't open) they'd have to crawl through the tiny air holes and that would be impossible - so they'd definitely be trapped inside the stove. The caps on my gas FPs all have 1/4 inch metal mesh, so that stops any critters from even getting in. So possibly a different cap would keep anything from even getting in the stove.

As far as actually getting in the house -They can squeeze into some pretty small openings in eves, gaps between chimney and house, etc. I had one get into a wall through a gap in an eve which was maybe 3/4 inch or 2cm for north of the border. Tiny little gap between the eve and a masonry chimney.

 

[Lee Batchelor]

I'd think a bat could certainly get down the flue. Typically what I have seen... bats, birds or whatever... once they start in the flue, they can't effectively fly, so end up tumbling clear to the bottom. So even a brief exploration of the opening tends to trap them and send on a 1-way trip to the bottom.

What would be less clear is how they would get out of the stove. I don't know what specific model you have, but in my stove (assuming the front door isn't open) they'd have to crawl through the tiny air holes and that would be impossible - so they'd definitely be trapped inside the stove. The caps on my gas FPs all have 1/4 inch metal mesh, so that stops any critters from even getting in. So possibly a different cap would keep anything from even getting in the stove.

As far as actually getting in the house -They can squeeze into some pretty small openings in eves, gaps between chimney and house, etc. I had one get into a wall through a gap in an eve which was maybe 3/4 inch or 2cm for north of the border. Tiny little gap between the eve and a masonry chimney.

Thanks, Corey. I can see how they could fit down the B-vent. I'm going to take the top off the stove and see if there is a way to escape it into the stove itself. The model number is SDV30, installed around 2000. I uploaded the manual but am not sure from the diagrams if a bat could escape.

 

[DAKSY]

If you have a co-axial vent on your stove, it’s NOT a B-vent. It’s a Direct Vent (DV). The should be no way for a bat to get into the vent, then into your stove & then out of your stove. It’s a sealed combustion system. If the vent is installed properly, those bats are getting in thru another method.

 

[Lee Batchelor]

Thanks for the clarification, Bob. You're 100% right. I did a thorough inspection of the pipe and how it terminates in the stove. There is no way they can escape the stove, even if they have dropped down by accident or other means. I had the cap off a week ago and took a picture. It's attached.

I ended up calling a pest control company and the man said bats first infest your attic and then can invade the living space only by accident. They don't want to be there. Trying to find out how bats enter from the attic to the living space is very difficult and is basically a waste of time. The key is to evict them from the attic by sealing off its entry points. Our brick is a rough surface so the j-channel for the soffit and brick does not form a seal small enough to prevent entry. I sealed the entire perimeter with a flexible caulking and will install "bat doors". These allow bats to leave at night but not get back in. From there, they find more natural habitats for their daytime sleep.

Just thought I'd throw that last bit in so if anyone else has bat issues possibly related to combustion products, it may provide some information. Thanks again for the help, everyone!

 

[rwh63]

thank you for caring about bats!

 

[Lee Batchelor]

thank you for caring about bats!

Thanks. They are ugly and I hate them flying close to my head but we sure need them to keep the mosquito population down! It's amazing to see them flying against the dusk sky. They can shift back and forth in an instant. My friend told me that's how you distinguish between a bat and a bird in the early evening. A bird will fly a linear path, whereas, a bat will zig-zag as it picks off bugs. Amazing!

 

[Lee Batchelor]

To rwh63's point, about a week ago is when I first encountered two large adult bats in the house. I was able to lock them into a bedroom. Later, my friend came over to help trap them. He is well versed in the problem. He quietly went into the room and one by one, caught them in a beach towel, and then took them outside and gently dropped them off our deck so they could take flight. Our deck is about 6 feet off grade - perfect for freeing a bat 😉.

Sorry for drifting off topic of gas stoves a bit 😁.

 

[rwh63]

Thanks. They are ugly and I hate them flying close to my head but we sure need them to keep the mosquito population down! It's amazing to see them flying against the dusk sky. They can shift back and forth in an instant. My friend told me that's how you distinguish between a bat and a bird in the early evening. A bird will fly a linear path, whereas, a bat will zig-zag as it picks off bugs. Amazing!

beauty is in the eye of the beholder, and i think they are awesome in appearance! of course, humans are the only animal that judges others worthiness by visual appearance, and thus countless animals (and humans!) suffer needlessly due to this discrimination. live and let live is my general motto.

 

[Lee Batchelor]

beauty is in the eye of the beholder, and i think they are awesome in appearance! of course, humans are the only animal that judges others worthiness by visual appearance, and thus countless animals (and humans!) suffer needlessly due to this discrimination. live and let live is my general motto.

👍👍.

 

[stoveliker]

I made a bat box back in TN. Supposed to be able to hold 400 bats. Hung it in a tree according to the recommendations of some bat society I found online.
Useful because the white-nose syndrome was killing them quickly. Smaller colonies means less spreading of that disease.

I read they eat 1000 mosquitos a night. 400 times 1000. Half a million less bugs every night. Half a million bugs per night not bothering me makes me kiss the ugliest thing...

I was always taught that it's best to simply open a window. Birds don't know a closed one from an open one, but bats do (visual vs sound navigation). Close the door of the room and have a window open, and they'll fly out when it pleases them. They won't come back in as there is no indication of food in the room for them (unless you have a corpse rotting in the wall and the flies have started ...).

The reason I'm saying this is that bat wings are very sensitive; even handling with a towel might scratch, damage them. They are rather fragile.

 

[Lee Batchelor]

Great info, thanks stoveliker. We tried opening a window but the bats kept flying in their typical U-shape and wouldn't exit. Later I discovered we should have dimmed the light in the room. I had it on full thinking they would aim for a darker zone, even though they are 90% blind. Crazy little creatures!

 

[stoveliker]

Interesting, that they respond so much to the light. Didn't know that.
Worth a try next time one is inside: see if the open window and switched off lights works.
I did not have lights on, and the one I had inside (small one, fist sized) flew out within a few minutes.

 

[Lee Batchelor]

Yes, I read that thing about the light on the internet. Interesting.