Silo Gazebo - Smoke Problem

jmc · Nov 16, 2021

Is that 2' hole in the top just a hole to the sky or is it capped a few inches above the main roof, leaving a circumferential vent?

mikester · Nov 16, 2021

You need a hotter fire. Run it hot, then convection will take over. Run it cold and choke yourselves.

No different than house chimneys - if you only run occasional slow fires you get tons of smoke and no convection action.

LouNY · Nov 16, 2021

A lowered hood and stove pipe chimney would vent much better then your existing setup,
or a draft fan installed at the top pulling out.

alexpops · Nov 16, 2021

Hotter fire (maybe) or the exhaust fan/lower hood options. As I see it, the smoke is cooling too much on it's way to the vent (air gap & metal roof helps the cooling), so you never really develop a draft. Even with a lower hood/exhaust fan, you might wind up sucking in more cold air from the open sides than your fire is putting out. Basically, what you got there is a drafty smoke house ... good for meat preservation, not so good for hanging out with beers.

deezler · Nov 16, 2021

Look at how it's done in big ski lodges, etc. You need a chimney pipe and hood that hovers somewhere around 3 to 5 feet above the fire pit. It has to be low enough to get warm, so that convection takes over.

But I also second MossRoad's suggestion to build a fire pit with secondary air injection, so that your fire is nearly smokeless to begin with. Burning clean is good for heat btu's, wood efficiency, carcinogenic smoke from partial combustion, air pollution, etc.

BackRoad · Nov 17, 2021

Suggest first to simply try taking any cover you have over the center vent off as a test to see if the opening is too restricted for effective smoke extraction.

Is there any air flow or vents between your eves and the metal siding?

Might be as simple as adding vents under the eve to allow air flow in the upper area above the metal siding.

Warm air will rise...it may just need additional venting around the roof edge to enable enough draft to pull the trapped smoke out.

The earlier suggestion for a basic, quiet exhaust fan at the top may be enough to get the flow started if adding vents at the eves does not fix the issue.

Nice set up by the way...it looks laid back and inviting!!!

MossRoad · Nov 17, 2021

I'd caution about putting a fan in the top. Unless it's a high temperature fan, it's gonna cook. All the heat that rises under that metal funnel shaped roof from even a moderate fire and forced through a fan will not end well. Has anyone else, ever, seen a fan in a chimney? That's what it is. A Chimney.

KennyG · Nov 17, 2021

They do make extraction fans for chimneys but they are quite expensive. I took a quick look at the garden variety duct fans and they are only rated for 140 deg F ambient, so not a great choice. I think the idea of a simple hood to go over the fire at a reasonable height would work pretty well. It would allow the opening in the roof to be closed in around the chimney with a chimney cap also.

MossRoad · Nov 17, 2021

KennyG said:
They do make extraction fans for chimneys but they are quite expensive. I took a quick look at the garden variety duct fans and they are only rated for 140 deg F ambient, so not a great choice. I think the idea of a simple hood to go over the fire at a reasonable height would work pretty well. It would allow the opening in the roof to be closed in around the chimney with a chimney cap also.

I knew about high temp fans because I put a "normal" duct booster fan in a duct over my wood stove in the basement up to the living room on the 1st floor. It cooked. I got a high temperature one and that works fine, but still cooks out after 5-6 years.