Wood Boilers and Fire Hazard Due to Roof Vents

[eauzonedan]

.......First Post........woo woo......there goes my cherry.......

I'm in the process of installing a Garn in what will be a full time 2-story residence up in No Wis. It's intended to be placed in the isolated end of the first floor walk out (a former garage). The flue will run on the outside of the exterior wall (penetrating the overhang) and extend above the roof (per codes) to minimize any "stinkeys" getting into the living space. My question revolves around the prevention of any small sparks or embers from finding their way into the vented attic space via a continuous ridge vent. I see a lot of info on wild fires out west and the involvement of various venting systems - but very little on solutions to the problem. My current 15-20 year old - shingle over ridge vent has a plastic "filter" that consists of +/- 3/16" wide slits running perpendicular to the ridge. It's dense enough to keep most pine needles from getting thru. I'm going to re-do the roof as part of my construction project anyway and wondered if anyone has knowledge of any "better mousetraps" that may be available. I currentlly have a monster Jotel I've run for about 10 years and have yet to have a problem.....but any kind of attic fire up there would tend to ruin my day.... I understand it's a long shot I'd have an issue, but I tend to lean in the direction of a belt and a pair of suspenders when it comes to burning the wrong wood.......

Input from the "brain trust" would be appreciated.......
Dan

 

[Willman]

I thought the Garn could vent horizontal piped down into a drum. I am sure the Garn owners will be along.

Will

 

[bpirger]

Dan, I have a 1500 which I vented horizontal, down into the garabage can. It is very clear that one DOES seem small sparks from time to exiting the flue, the 90 done, and in my case blowing up and out of the can. I have yet to place any screen over the can or anything inside the can. I installed in NOV and have had a snow blanket since that time...still do...but not for long.

Kemer on here has a vertical 2000 and i know he has concerns regarding seeing some sparks from his stack as well.

I've burned my Lopi for years, and one thing or another for 35 years, without everything thinking about sparks getting into the ridge vent. I do wonder about them getting into the nearby spruce trees.

How far away is your stack going to be from the vent? Are you worried about nearby dry surfaces, i.e. vegetation or similar, or just getting into the vent.

Clearly there appears to be more sparks exiting the flue with the forced fan than I have ever seen from a stainless chimney and the natural draft of the woodstove.....

I don't really have any great answers for you...other than indeed there are some sparks that will fly out, and around, in the flue exhaust. I don't think I've ever seen them last longer than a second or two to my naked eye...and can only see them at night time....

I guess my answer is I wouldn't worry too much about them sneaking into your ridge vent unless you are directly blowing right into it...nearby....but the concern regarding general contact of said sparks exists...and I'm not sure anyone has suggested/develop a sure fire way to either trap them all or guarantee no issue. Fires have been started by Garn exhuast I have been told, though these cases were always user stupidity. Someone was trying to dry out their next load of firewood for example...but placing it in the exhaust...and apparently it ignited. Though, I wouldn't really think it would ever get quite hot enough for this directly....so perhaps there was something bigger coming out? This story was told to me by a Garn dealer...don't know any details...but interesting.

Others will chime in...welcome to the site!

 

[eauzonedan]

Appreciate the response......it's a 1500 and will go horizontal thru a block wall ....then vertical with a 90. I didn't think a presurized fllue inside the building envelope was a real great idea - and why I didn't go with a vertical style unit. The flue will penetrate the roof about 7 feet (horizontal distance) away from the peak. At the point of roof penetration - I'll be about 2 feet below the peak and to try to maintain a top stack height of 2 feet above the peak (which is less than 10 feet away)........all of which translates to about 4 foot of stack above the point of penetration. Since it's not a gravity exhaust it was suggested I may not have to hold to the two feet, but think it's still my target to keep the insurance guys happy and not get into an argument with them......Their approval is based upon compliance with the manufacturers manual.......and that says 3' above the point of penetration and 2' above anything within 10'........... The building has a 2' overhang on the end and with the flue - so the flue will be near the roof edge. The current ridge vent runs the full length of the building.

On the ground - I've got about 50 ' + clear to any vegitation, but it turns into pine forest beyond that......I guess spring time is the scarey time up there ....before things green up....... and yes setting the woods on fire is another issue if threre's no white stuff out there......... With the height of the stack and the distance to the trees - I should have a pretty good "hang time" before anything could float into the woods........Not so true with something getting thru the ridge vent however..... Maybe I'm just overly cautious......

Dan

 

[Duetech]

To my knowledge the roof vent on our house has a screen built in to prevent insect invasion sparks would stop there too. To ease your concerns perhaps you could buy a roll of aluminum screen and cut it into strips you could tuck into the vent opening. The roof would still vent but you would then have a spark barrier that is hidden away on the outside and was not an eyesore. As fas as the wild fires I would think the problem there was more from embers sent aloft by the torrential updrafts.

 

[Kemer]

Eauzonedan
Yes I have a Garn 1500 with a vertical chimney.I do get some spark's that you can only see at night.My set sounds like yours as far as distance from roof vent.Keep in mind that you are limited on how high you can go with a vertical chimney.I believe it's 12 ft.I have watched my chimney at night and the sparks don't go much more then 5 ft when they exit but I'm still not happy and I don't think you will be either. My problem might be my intake pipe has to many elbows and I am waiting for the heating season to slow down and change it.Garn claims that will help but other guys with horizontal setups still see a spark or two so I have my doubts.But I must say I don't get any smoke lingering and other then that what a great boiler.One good thing I have going is the wind blows it away from my roof vents.I have had over 300 fires in my garn so far and it really seems to burn clean and also I never seen and ash or soot on my snow covered roof for what that's worth like I did with my Eko.Keep me posted on how you make out.

Harry

 

[woodsmaster]

.......First Post........woo woo......there goes my cherry.......

I'm in the process of installing a Garn in what will be a full time 2-story residence up in No Wis. It's intended to be placed in the isolated end of the first floor walk out (a former garage). The flue will run on the outside of the exterior wall (penetrating the overhang) and extend above the roof (per codes) to minimize any "stinkeys" getting into the living space. My question revolves around the prevention of any small sparks or embers from finding their way into the vented attic space via a continuous ridge vent. I see a lot of info on wild fires out west and the involvement of various venting systems - but very little on solutions to the problem. My current 15-20 year old - shingle over ridge vent has a plastic "filter" that consists of +/- 3/16" wide slits running perpendicular to the ridge. It's dense enough to keep most pine needles from getting thru. I'm going to re-do the roof as part of my construction project anyway and wondered if anyone has knowledge of any "better mousetraps" that may be available. I currentlly have a monster Jotel I've run for about 10 years and have yet to have a problem.....but any kind of attic fire up there would tend to ruin my day.... I understand it's a long shot I'd have an issue, but I tend to lean in the direction of a belt and a pair of suspenders when it comes to burning the wrong wood.......

Input from the "brain trust" would be appreciated.......
Dan

As long as you have vents in the soffit ( under overhangs ) the ridge vent should be expelling air therfore It wouldnt be trying to pull a spark in.

 

[afblue]

How many ft of vertical chimey will you have when you install your garn?

 

[eauzonedan]

The distance from the first floor slab - to the roof peak is about 22' 4". I'm currently down in IL and the Garn is sitting on a trailer up in WI. Based on my printed info in hand - I estimate the height of the centerline of the horizontal flue above the Garns base - at a bit under 4' .......So 22" 4" + 2' (flue height above the peak - 4' (flue above the 1st floor slab) says about 20+' of vertical stack.....plus the 90 degree bend at the bottom......plus about 3 to 4 ' of horizontal - out the back of the Garn to get thru the wall and give me a bit of working space behind the unit....... My initial information was "no problem....there is no restriction on vertical flue height"......now I'm starting to hear that between friction losses and cooling of exhaust gas......I may be bumping against a problem......... At this point I'm working on that with a consultant and trying to investigate if enclosing the outside portion of the flue may help the cooling issue as well as if it's possible to counteract the friction losses via a blower tweak or maybe enlarging the inlet side plumbing.......... I gues I can't believe I'm the first guy that wanted to stick one of these in first floor of a two story building.....although most wouldn't have the benefit of a former walk out level garage that would easilly accomidate it..... Early in the project - I noted that the install manual limited connection to a vertical masonary chimney to "no taller than 24'. When I asked about that restriction I was told that was because of possible friction losses from the required 6" stainless liner which had to be placed inside the masonry- and there was otherwise no vertical height restriction with the DuraTech pipe...........So at this point I'm still trying to work thru stack heights - and make sure everything is workable.

anyway.......
The reason for this post was originaly to inquire if anybody had any experience with any newer types of roof vents. The research coming in from some of the forest fire losses out west was suggesting some changes in the works for them via metal screens/filters and some baffle arrangements to trap embers. I was trolling for input as far as knowledge or experience with such items. One early suggestion I heard was to consider eliminating ridge venting in the area of the flue and go with a gable vent on that end of the building. As I dug into that - I discovered you can get some wierd air currents and mixing the two (ridge and gable vents) is not recommended. The discussion started to move away from my vent question a bit, but it's still pertenant to my install and much appreciated.... I'm pretty green at most of this and do appreciate input from those that "been there and already done it"

Dan

 

[Willman]

Spray foam the underside of the roof deck for a "hot roof" if the space below is conditioned. Then close the rdige vent, no worries. Better insulation to boot means less wood burnt

Will

 

[Como]

Horizontal exhaust is not always an option is you have an existing building with combustible siding,

 

[afblue]

eauzonedan-
Addressing mixing of gable and ridge vents, you are correct, I would not advise mixing them. It was the topic of a Holmes on Holmes episode, and I saw it personally as it's what prematurely ruined my bosses roof. He had ridge vent, and in the effort to vent a Victorian style hip roof house, he added a powered vent, what ended up happening was the vent was drawing air in the ridge vent and blowing it out the vent, which in turn stopped the air flow up from the eves and baked the shingles about 5-10 years early.
I have no experience with Garns so I am not much help with them, I just figured the more vertical stack you have, as long as the gases dont cool off too much, you would have more time for the sparks to burn out, and you wouldnt see the embers like people are with a garn with short or horizontal stacks.

 

[NCPABill]

I'm with woodsmaster on this one. Did you ever notice that the snow melts just a little right next to the ridge vent? Or the powdery snows seem to never plug over along the edge of the vent. I'd put up the correct chimney set-up and sleep tight.

Good luck on the project,

Bill