# My outside hot air furnace project



## dave_dj1 (Nov 18, 2010)

I had this Fawcette hot air wood furnace given to me last summer, I don't realy have room in my garage for it so I decided to make due, and put it outside. 





The silver stuff is called Reflectex, it has a class 1-A fire rating so I figured it would be a good barrier to prevent thermal transfer from the siding to the furnace. 
First thing I did was to build and insulated base, 2" high R sheathing sandwich'ed betweeen 2 layers of 5/8 plywood, covered by a piece of dura-rok. Keep in mind that most of the stuff I used I had lying around except the steel studs and the reflectex and stove pipe.









my brother had just taken down a tripple wall chimney, 10" inside and 15" outsied, I made some pieces to cover the ends and filled in between with vermiculite for insulation, these are my hot/cold air lines to the garage.








my brother also had this piece of ductwork,




I've had this blower for years, not knowing what I needed it for..lol


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## dave_dj1 (Nov 18, 2010)

after I framed it with 3 5/8" steel studs, I insulated it with R13 fiberglass insulation, then another layer of the reflectex.








It has a 7" stack, I put a 10" over it and filled with vermiculite, trying to keep the chimney warm, the top part is reduced to 8" over the 7", air insulated.
I am using it now, it works great after installing a new fan limit switch.
I have a couple of finishing touches to do , I will post a few more pics as soon as I get her finished up.


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## Beefie (Nov 18, 2010)

Neat project, it will be interesting to see how it works over the winter. If you have more pics post them up we like pics here lots of pics:hmm3grin2orange:


Beefie


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## beerman6 (Nov 18, 2010)




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## Jredsjeep (Nov 18, 2010)

nice! thanks for sharing, look forward to seeing it work!


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## grapplermi (Nov 18, 2010)

That looks really cool, should work nice. Good job.


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## iowa (Nov 18, 2010)

TreeCo said:


> I love your enthusiasm but I've got a one word solution for heating with wood around here: Jotul.
> 
> No wires...no fans...no ducts...higher efficiency......no heat lost to the outdoors......great fire view.....3 days fuel supply sitting on the hearth...etc.



Sooooo. Is this a stove. I can load my furnace and not worry about it for 12 hrs. House is still 76 deg. This is on a 3000 sq ft house. How many times would u have to load a jotul?


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## pook (Nov 18, 2010)

watch for embers from the chimni landing on the shigle roof?


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## flotek (Nov 18, 2010)

do i have this right? looks like your using thin ducting for a chimney pipe but using the triple wall for your ductwork ? sounds kind of backwards


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## dave_dj1 (Nov 18, 2010)

flotek said:


> do i have this right? looks like your using thin ducting for a chimney pipe but using the triple wall for your ductwork ? sounds kind of backwards



the chimney pipe is 7" heavy stove pipe, with a 10" stove pipe over it and vermiculite in between. My thought was to keep the smoke warm to the top to avoid any creosote. If I have to replace the pipe in a year or so it's no big deal, I may stumble across some metal-bestos pipe. 
As far as embers on the shingle roof, It has crossed my mind, the furnace has a huge heat chamber that the smoke goes through before going out the chimney so the risk is minimal and, the whole thing is actualy big for my little garage so I have only been putting small amounts of seasoned hardwood in it at a time, maybe 2 sticks, I've been using it since last Sunday. I only light it when I'm going to be in there, I never have it going when I'm done unless it's just a few coals. So far it works awesome!!
I will post up some more pics this weekend, been swamped with work so I haven't put the finishing touches on it yet.

As far as using a jotul, I have NO room in the garage! Or do I want the sparks, i weld and paint and fab parts for my trucks, jeep or buggy. I need all the room I can get.

Here's a link to my latest welding project.
http://www.rok-freekz.com/forums/viewtopic.php?f=14&t=1996


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## scotvl (Nov 19, 2010)

TreeCo said:


> I love your enthusiasm but I've got a one word solution for heating with wood around here: Jotul.
> 
> No wires...no fans...no ducts...higher efficiency......no heat lost to the outdoors......great fire view.....3 days fuel supply sitting on the hearth...etc.



where I live my insurance co made me remove my wood stove in the garage (they said you cannot have a wood fired heater anywhere fuel may be stored) I wonder if this would be ok?


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## Justsaws (Nov 19, 2010)

scotvl said:


> where I live my insurance co made me remove my wood stove in the garage (they said you cannot have a wood fired heater anywhere fuel may be stored) I wonder if this would be ok?



It is not where I live. No property/fire/liability insurance on home made or non-UL/etc. heating devices. 

No (inexpensive)insurance on out buildings with wood burners installed in them. Specific policy addition with limitations for residential applications. Do not know about farms/business. 

Most folks that installed the out door wood boilers that I have talked to did not even ask their insurance company about coverage. When I asked the answer was "NO" or "Yes, but ..." which equaled more $$$.


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## dave_dj1 (Nov 26, 2010)

well it was finally cold enough here (low 20's) yesterday to see how the unit performs, all I can say is AWESOME! :hmm3grin2orange:

I have a couple of pieces of siding to put on and I will get some more pics up.


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## scag52 (Nov 26, 2010)

Very nice . I like the whole idea . No water to worry about. I had a stove in my shop and always thinking about those fumes exploding.


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## dave_dj1 (Dec 8, 2010)

More pics as promised, I have been using this all week and it's only made it into the 20's and I'm quite pleased. My garage isn't that big but I do have a makeshift addition on the OH door end, I'll try to remember to take a pic of that, it's like the bonnet on a babies stroller, it lifts up and down so I can drive my truck part way in to work on it. It's made out of reinforced 6 mil poly.


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## Erock (Dec 8, 2010)

dave_dj1 said:


> More pics as promised, I have been using this all week and it's only made it into the 20's and I'm quite pleased. My garage isn't that big but I do have a makeshift addition on the OH door end, I'll try to remember to take a pic of that, it's like the bonnet on a babies stroller, it lifts up and down so I can drive my truck part way in to work on it. It's made out of reinforced 6 mil poly.



wow you did a really nice job on that. rep comming your way


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## caleath (Dec 29, 2010)

Nice job enjoyed reading it.


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## dave_dj1 (Dec 30, 2010)

Thank you all for the props!
My only concern now is finding enough firewood this time of year to keep it going. I do have a friend that has a log yard a couple of miles away and he was kind enough to fill my truck with butts a week or so ago. I have just splitting it up by hand as needed. I borrowed a splitter from my brother yesterday but ended up throwing my back out trying to start the darn thing (it was left with an empty tank of fuel). So until my back heals up, I won't be burning the furnace for a while.


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## Henry and Wanda (Dec 30, 2010)

I really like the job you did....very nice work......you should be proud !!!!!!!!


Henry ans Wanda


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## dave_dj1 (Feb 23, 2011)

Well after aprox. 3 months of intermittant use, I am here to tell you I couldn't be more pleased with this unit! I only burn it when I have a project going on in the garage (which has been often this winter). I have kept it going for up to 3-4 days at a time and it works great! I haven't had to make a single adjustment or alteration on the unit. I have had to learn to adjust the amount of wood I chuck in it, I have to keep a close eye on the outside temps. If it warms up too much and I have a good amount of wood in it, it get's too hot in the garage and I have to open a window...LOL 
My buddy has been keeping me supplied with wood, I have been busy working it up and now I need a larger saw! 
Happy burning


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## Blazin (Feb 23, 2011)

Good deal! Nothin better than a warm garage to work in!


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## Putter (Feb 23, 2011)

Very nice and tidy. You did a good job. Any details where you mounted the blower and pictures of the heat exchanger and firebox would be interesting.


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## dave_dj1 (Feb 23, 2011)

Putter said:


> Very nice and tidy. You did a good job. Any details where you mounted the blower and pictures of the heat exchanger and firebox would be interesting.


 
Thanks 
In the first and third pic on this page (page 2) you will see a little brown section of siding, the cold air is on the bottom, blower sits inside the bottom, if you look at the first set of pics on page 1, the base has a spot sticking out for the blower to sit. The wood furnace itself I did not build, it is a Fawcette, still made in Canada. The heat exchanger is on top of the firebox and is round, as well as the firebox being round. There is NO water running through this unit, strictly hot air. 
I am contemplating finding antother similar unit and building another one for my house. I think it would pay to buy a brand new one and start from there. I am scouring CL in hopes of finding a suitable unit for the house. If I can't find another one that I like I may move this one to the house for next winter and still keep searching for another similar unit.


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## Dustinthewind55 (Nov 4, 2014)

dave_dj1 said:


> Thanks
> In the first and third pic on this page (page 2) you will see a little brown section of siding, the cold air is on the bottom, blower sits inside the bottom, if you look at the first set of pics on page 1, the base has a spot sticking out for the blower to sit. The wood furnace itself I did not build, it is a Fawcette, still made in Canada. The heat exchanger is on top of the firebox and is round, as well as the firebox being round. There is NO water running through this unit, strictly hot air.
> I am contemplating finding antother similar unit and building another one for my house. I think it would pay to buy a brand new one and start from there. I am scouring CL in hopes of finding a suitable unit for the house. If I can't find another one that I like I may move this one to the house for next winter and still keep searching for another similar unit.


I realize this is an old thread but I am in the process of doing this exact same thing and have ran into one roadblock after another. This thread has helped me a bunch but there are still things I'm not quite sure about and would love to ask someone that has been there done that. My big question right now is...are you basically using the building that you built around the furnace as a second jacket? And what I mean is the building sealed tight enough that you actually have your heat duct coming out of the building as opposed to out of the top of the furnace? Or is it hooked up as it normally would be if it were inside the home and if so does the heat inside the building itself cause an issue? I hope I am making sense.


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## Marshy (Nov 4, 2014)

Dustinthewind55 said:


> I realize this is an old thread but I am in the process of doing this exact same thing and have ran into one roadblock after another. This thread has helped me a bunch but there are still things I'm not quite sure about and would love to ask someone that has been there done that. My big question right now is...are you basically using the building that you built around the furnace as a second jacket? And what I mean is the building sealed tight enough that you actually have your heat duct coming out of the building as opposed to out of the top of the furnace? Or is it hooked up as it normally would be if it were inside the home and if so does the heat inside the building itself cause an issue? I hope I am making sense.


It appears to me that he used the normal ducting from the furnace unit an only added the structure around it to protect it from the elements and provide some insulating protection from the cold. The front door as air holes down in the bottom of it for combustion air to the firebox... Just what I see, hope that helps you if he does not respond 

Very nice work BTW.


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## dave_dj1 (Nov 5, 2014)

Kind of both, the structure is insulated and sealed too. I wrapped the furnace with a product called reflectex, it's like bubble wrap.
One thing I found is that the air travels so fast through the ductwork that in reality, you don't need any insulation. The only downside I see to no duct insulation is you would get a shot of cold air initially. I wouldn't have that problem as my blower hardly ever shuts off!
To do it over again the only thing I would really change is the top, I should have had a larger size plenum on the top, I think the close tolerance I have is why the blower runs almost constantly.
Good luck and ask away. I don't think I have any more pics but I am willing to answer any questions I can for you.
dave


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## Dustinthewind55 (Nov 5, 2014)

Thanks Dave and Marshy for getting back with me. I tend to over analyze things and have spent the last couple of weeks trying to figure out just what to do. I am familiar with the reflectex and will use that for sure. I also agree about the air traveling fast enough to not really cool it down a bunch in fact a guy down the road that once sold wood furnaces thought it might be more important to insulate the cold air return. We are primarily wanting it to heat a large family room so I doubt I will fire it really heavy nor expect it to hold coals for a long time. My biggest concern is the heat inside the building itself. I know there is conductive heat from the furnace jacket and with no way for it to escape I wonder about the wiring. Have you ever noticed that being a problem? I also thought today that I would build in an access door in back as well as the front in case it becomes necessary to vent the building for any reason such as a power outage. Is your blower located on back of the furnace blowing through the jacket or is it in the square box at the top of your furnace sucking air through it? I'm sure I will come up with more questions as time goes on....thanks again for your input.....Steve


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## dave_dj1 (Nov 6, 2014)

Dustinthewind55, if you go back and look at the 8th picture down you will see my cordless impact gun, that is where the fan sits, it blows in to the jacket and comes out the top square. No real reason for that big square box other than my brother gave it to me. The jacket is insulated, my walls are built tight to the reflectex and then wrapped with fiberglass insulation. To do it again I would make the walls about 8-10" thick for max insulation. The peak I just stuffed full, snow will sit on the roof for a while, I'm sure there is some heat loss. To me the idea is to keep as much heat in the jacket/furnace to use in the house. The only venting I have is in the bottom of the door for air intake for the fire. It's 34 out right now and 73 in here  I only lit the thing at 8 last night and stoked it at around 10. I'm heating a walk out ranch which is a total of sq ft of about 1900. I do have good windows and some extra insulation in the attic and we sleep with the bedroom window open about 2:. LOL
Again, anything you want to know just ask. I'll do my best to answer.
dave


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