Do chimney caps = excessive creosote buildup?

If you are talking about a standard hat-type chimney cap, the answer is NO - it should not cause any creosote buildup....probably a coincidence.

A cap should actually HELP in most wind conditions. If you want a little heavy studying, this shows some tests:
https://www.hearth.com/econtent/index.php/wiki/Effect_of_wind_on_chimney_caps/

basically, a cap is better than no cap in most wind conditions and directions.

Burn properly seasoned wood.

What about no wind - wouldn't a cap reduce chimney draft at least a bit?

j-train said:

it is a regular cap, mesh with a top on it. mesh is 8" high. i always burn seasoned wood and never had cresote buildup until i added the cap. maybe i will have to take cap off for winter and put back on in spring

Click to expand...

Lets think this through.

The cresote is comming from the fire. No big deal but it stands to reason that either what you are burning or how you are burning is letting this cresote come to be. Well, OK, cresote is a big deal but you can do something about that.

Perhaps you live where it gets real cold and the cap is up there where it can get chilled out enough to let the cresote to condence on it. Perhaps the cap is cool enough to let some of it fall back down the stack. I'm having to assume a lot here. Not that any of that matters, but just a guess at what is happening up there.

The root of the problem is you got something causing cresote even if the cap is there or not. I'm gonna say we need to solve that problem. It could be the wood is too green. They say here if the wood is over 20% some say 24% moisture your asking for trouble. You can get a little wood meter for $20 and they say it works great. I need to get one myself. You will get more heat and have less to worry about doing dry wood and the meter will help you know if the wood is dry or not.

Your stove or fire place may be jacked up (messed up), (please excuse my hillbilly language and spelling). If the wood is good then something is wrong with the fire box or the set up. Hey take pictures of it and show these people. There is people here that live for helping you out with that stuff.

When we get rid of the cresote, you are gonna be way better off. More heat, a better fire, and none of that cresote to worry about. That is the right thing to do right now.

I would say that yes, a mesh cap can cause creosote to form on the mesh, this plugs up the chimney which can destroy the draft which will make even good wood burn poorly. The now poorly burning wood can creosote up your chimney. I started out with a mesh cap and then after having to clean the mesh out a few times I went ahead and removed the mesh but kept the cap. I had good wood and the chimney never saw any substantial buildup. That dang mesh is your problem.

Trouble is that you might be required to have the mesh to act as a spark arrestor.

branchburner said:

What about no wind - wouldn't a cap reduce chimney draft at least a bit?

Click to expand...

Yes, in theory, when the wind was at 5MPH or less, a cap would act to slightly reduce draft - but in winter, it is rarely that still.

The mesh screen is a spark arrestor. They are defined quite specifically in NFPA 211 4.6.3, and are required in some jurisdictions. I suspect the folks who manufacture chimney caps simply put them in as a matter of course, since they've no idea where any specific chimney cap is bound. If a spark arrestor is not required where you live, then you can take the screen mesh out & replace the cap on the chimney without it. Rick

j-train said:

I installed a chimney cap a year ago and when I cleaned the chimney, it was the worse creosote buildup I had had in the 5 years we've lived here. Is there any way to get around this, or should I just take it off? Why does it do this? I originally put it on because of leaks and put on the tallest cap I could find. Thanks.

Click to expand...

Going back to your original question... is this a masonry chimney? Did it ever have a cap before this? It sounds like it did not and you have a water problem. A simple cap will be an excellent effort towards solving the water problem. The mesh on the cap is a restriction and does nothing for your water problem while causing a restriction that gets worse and worse as the creosote and other junk sets up on it.

You chose an aftermarket cap from the shelf at a store. You could have also chosen a design that had no mesh. How is removing the mesh you have any different than choosing the meshless one?

As stated in my previous post, the mesh screen is a spark arrestor. It is required in some jurisdictions. If you have a shake roof or live on wooded property, it's a damned good idea to leave it installed. In any case, the chimney cap/spark arrestor screen are not a source of creosote, just a nice cool place at the top of the chimney for creosote to condense out. The creosote is being produced in the appliance at the bottom of the chimney. Maybe the spark arrestor is trying to tell you something about the wood you're burning or the way in which you're burning it. Got a stovepipe thermometer? Rick

The mesh screen is not just a spark arrestor. It is a bird blocker too. It can make an otherwise clean burning fire turn into a creosote maker by condensing out crap that would have normally made it to the sky. That condensed out crap will obstruct the chimney's flow path, reduce draft, and further create creosote in the system.

If J-train never had a cap or spark arrestor before then why should he be required to put one on. Many many people, perhaps the majority, do not have a mesh cap on their chimney. A plugged up mesh cap is not conclusive evidence of poor burning but I will agree that a poor burner will plug one up very quickly.

"As stated in my previous post" Then why must you repeat?

I like my screened cap. Especially in the woods here. I would hate for my place or worse yet have to explain to my neighbors why embers that came from my chimney caused our woods to burn or their homes worse yet. If in fact that ever happened. Hasn't yet, and prolly won't cause I leave my screen on. There are a couple things you can do to keep it from getting clogged. First is burn truly dry wood. If your clogging that thing up that often, your NOT burning seasoned dry wood, period. The second thing is get this.................. clean the screen..................... I know its a stretch for some to fathom, but some folks actually do this. I cleaned my chimney & screened cap January of last winter, and burned damn near up till May here. I have fired the insert up a few times this past week also without cleaning yet. I will clean before 24/7 burning this season, but to this point, no clogged cap and drafting/burning fine.
It never ceases to amaze me at folks that think they are burning dry wood, but truly aren't.
To each their own, if you don't want to clean the screen, pull it off.
But I guarantee if the screen is clogged, you also have a nice layer of creosote at the top of that chimney.
As someone already stated, its a symptom of whats coming from below. Either burning practices, or the wood being burnt, or both.
Better to cure the cause of the symptoms, than cut off a limb.

O my gosh you guys with your "mesh vs no-mesh" are almost as bad the "cat vs non-cat" crowd
for the record I'm with the no-mesh crowd

I took my screen off for this burning season, (creosote did build up on it which reduced my draft last season) but will put it back on in the spring when we're done to keep the birds out. As long as you're not burning a lot of paper or garbage, you really shouldn't have any embers coming out of your chimney.

Like a lot of other things, I think it depends at least in part on where you live. When I lived in Northern Virginia, the climate was such that a spark or two flying out of the chimney from time to time probably wasn't a big deal...everything in the surrounding environment seemed to stay too wet & lush year-round to easily catch fire. Where I live now, in the dry high desert of central Oregon, we have annual cycles of very high fire danger (a common thing in "the West"). Fires do a tremendous amount of damage to the environment and to public & private property out here every year. The cost is significant, in many ways. The periods of extreme danger of wildfires frequently overlap the seasons of burning for heating in our homes. All it would take to start a very serious wildfire would be for me to stoke one of my woodstoves up and light it off without a spark arrestor screen installed in the chimney cap. Glowing embers do occasionally find their way up & out of the chimney without a screen. I observed it from my chimneys in Virginia many times. I'll keep my screens in place. If they accumulate enough creosote during the season that I think it's affecting draft, I'll go up and clean them. But I'll not just remove them to make my life easier if it places the environment around me at risk. We also have a code requirement to have spark arrestors installed here, and a lot of restrictions on outside burning. I tend to pay attention to stuff like that. Rick