Bats in stove pipes/flues

Is there a safe way to prevent bats from accessing these areas? I get requests for it now and then, but not sure there is a safe way to do it. I've seen home owners put quarter-inch screen over their standard caps, but it seems this could be dangerous in an ice storm.

A cap should overhang enough to protect the screen from collecting ice, especially if in use like a wood stove etc. Can a Bat squeeze thru 3/8 or 1/2" hardware cloth?

Not sure, I thought most use quarter inch for bat work. Anybody use 3/8"?

IMO a bat can squeeze through a 1/4 in hole. But the hole must have some length to it. Not a 1/4 in square. Like 1/4 in by 1 in. long. I don't think a bat can squeeze through a 1/2 in square. Much bigger, and little brown bats will go right through.

Would depend on species (size), reproductive status (a pregnant bat with one let alone two near term
pups isn't going through the same size hole an non pregnant female will or can, is the bat returning from
feeding or just getting ready to go out, all these and more still leave me saying... smaller mesh should mean
less potential.

We exclude of course, but we also survey bridges and culverts as well as rehab bats. We have had as many as 8 species
of bat in care at once from tiny myotis to Pallids and big brown and all bets are off if they are motivated to find a way in or out
of something that seems "secure" in terms of fitting.

I've seen plenty of bats get trapped and die after snagging a wing or forearm in a thin slot, but I've seen them pour out of
the same sized slot as well unfettered!

Bats are amazing at crunching themselves down to get into a roost. I'd ask how much warranty work you want to do, then decide
on the size of that mesh.

Bats constantly still befuddle me but i keep learning and learning and learning!

Good topic!

Have any of you actually screened chimney caps small enough to exclude bats? Sounds like I'd need to go 3/8" at most, maybe even 1/4". These are little brown bats. I'm less worried about warranty and most about safety.

My concern was that 1/4" might accumulate creosote and plug up too easily. Anybody have experience there?

Check with your building codes. I think 5/8 diamond pattern is the smallest you can use. If you use something smaller and there is a problem, I would not want to be your insurance co.

That's what I was thinking. 5/8 diamond is the smallest that I've seen available commercially.

Don't know why I didn't go straight to the code book....

R1003.9.2 Spark arrestors.
Where a spark arrestor is installed on a masonry chimney, the spark arrestor shall meet all of the following requirements:

1. The net free area of the arrestor shall not be less than four times the net free area of the outlet of the chimney flue it serves.

2. The arrestor screen shall have heat and corrosion resistance equivalent to 19-gage galvanized steel or 24-gage stainless steel.

3. Openings shall not permit the passage of spheres having a diameter greater than 1/2 inch (13 mm) nor block the passage of spheres having a diameter less than 3/8 inch (10 mm).

4. The spark arrestor shall be accessible for cleaning and the screen or chimney cap shall be removable to allow for cleaning of the chimney flue.