Silo Gazebo - Smoke Problem

[NCAlaskan]

Have searched around and cannot seem to find anyone with experience so thought some of you might have seen this before.

My cow hay guy gave me a 14ft silo which I have repurposed as a gazebo firepit hangout. See attached picture.
5 of 8 of the sections are open. The back three have panel to the floor. It is open about 8 foot up on the 5 sides. 32inches of panel around the top under the roof.

Here is the problem: the smoke from the fire doesn't vent out the 2ft hole in the top center. It sits under the top and then floats down to head level and vents out the side.

In my reading, I found people with outdoor fireplaces talking about heating a chimney. I don't have one to heat.
I also found suggestions about adding chimney height. I would rather not as it will look funny.

If it is a convection issue, would it help to put holes under the roof line. I don't like the idea of a fan but that would probably get flow going.

Any ideas?

 

[NormL]

Have searched around and cannot seem to find anyone with experience so thought some of you might have seen this before.

My cow hay guy gave me a 14ft silo which I have repurposed as a gazebo firepit hangout. See attached picture.
5 of 8 of the sections are open. The back three have panel to the floor. It is open about 8 foot up on the 5 sides. 32inches of panel around the top under the roof.

Here is the problem: the smoke from the fire doesn't vent out the 2ft hole in the top center. It sits under the top and then floats down to head level and vents out the side.

In my reading, I found people with outdoor fireplaces talking about heating a chimney. I don't have one to heat.
I also found suggestions about adding chimney height. I would rather not as it will look funny.

If it is a convection issue, would it help to put holes under the roof line. I don't like the idea of a fan but that would probably get flow going.

Any ideas?

I know you said you don't like the idea, but how about a ceiling fan like you see for living rooms and other areas. They are quiet, reversible, and come with light fixtures that you could "play" with for interesting effects.

 

[RickB]

You're either going to need a fan to force the smoke out or add a chimney so convection draws it out.
A third option would be a turbine vent if you have reliable breezes.

 

[MossRoad]

You could try building a smokeless fire pit. Doesn't look too hard.

 

[Captain Dirty]

What sort of fuel are you burning? With a good draft (as Moss Road's post shows) a seasoned, hardwood (oak, Hickory, and others) will burn almost smokeless. If, like many of us, you are burning damp, punky, half-rotten wood that would otherwise go to a burn pit or a composting gully, the fire will smolder rather than burn.

 

[NormL]

You're either going to need a fan to force the smoke out or add a chimney so convection draws it out.
A third option would be a turbine vent if you have reliable breezes.

I considered suggesting the turbine vent but in my experience, they're noisy and from the pic provided, the reliability of a consistent breeze is doubtful. The chimney option would probably evoke chuckles and references to the "Tin-man from Oz".

 

[RickB]

I considered suggesting the turbine vent but in my experience, they're noisy and from the pic provided, the reliability of a consistent breeze is doubtful. The chimney option would probably evoke chuckles and references to the "Tin-man from Oz".

It's not my gazebo so I'm not worried about "looks". That's for the owner to decide. The goal is to remove the smoke. He doesn't want a fan or chimney, my guess is he's either gonna learn to like smoke or go without fires.

 

[tomplum]

The smokeless fire pit idea works. On what I had built out of steel, I welded tube to the bottom and ran it out the side. It wouldn't take much to do the same here. Myself I would run steel tube or tile in a trench to feed the fire the O2 it needs to burn. It should reduce the smoke a fair amount.

 

[jmc]

Maybe an "inside chimney" that drops down toward, and is heated by, the fire; but not so low that it interferes with heads and sight lines? Larger inlet than your 2' outlet and tapered.

afterthought: elevating the fire pit would help with the above and might provide options for better combustion.

 

[mike0000]

A Cupola with an exhaust fan?

Mike

 

[jmc]

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]

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]

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]

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]

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]

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]

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]

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]

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.

 

[LouNY]

Just use an induced draft fan for a furnance;
Induced Draft Furnace Blower, 115 Volt: Replacement Household Furnace Motors: Amazon.com: Tools & Home Improvement