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workshop heating ideas. Answered

Hello all,

I have a slight problem, while designing my workshop for the winter months, I happened across a monumental problem... how am I going to heat it? As any Canadian reading this will know, our winters are not for the faint of heart (-50 anyone?), the structure I designed has a metal frame, HardiBacker lined inside and out as walls, screwed into the metal poles, fireproof spray foam insulation in between the cement board walls, it has been placed on a gravel surface, and is held to the ground by rebar that is nailed into the ground a few feet, and currently no ventilation. I know it has flaws left right and center, but I'm working with what i have right now, and I've got very little to work with. The structure is quite small 10' x 8' at 640sq. feet.

Winter is on its way and I need ideas for heating. I've thought about wood heating but I'll need all the space I can get on the inside. propane heaters are quite expensive, and electric heaters.... well its out in the middle of a field basically. Im looking for something that can heat it up fairly quickly, and is safe, I made it fireproof so i guess a tiger torch isn't out of the question..... 

Any suggestions are welcome!



Make an external wood heater. ;)

Take a standard pot belly or similar, create a nice enclosure around it and make a duct connection to your shed.

One duct on ground level with a fan that delivers the air from your shed to the outside enclosure.

The other a bit higher and connected to the top of you outdoor enclosure, leave a good lenght of flexible hose on it and you can place he hot air stream where you need it.

Works surprisingly well and provides even better heating that the pot belly sitting inside the shed as you have a forced air flow.

Just makes sure you insulated the ourside of the enclosure with some firproof material like rock wool so you don't loose too much heat to the enviroment...

thanks! but the only wood furnce i have at the moment is a little bit smaller than a love seat and takes two people with dolly's to move, the other thing is the fuel. I'm out of money, but i have half a forest behind my house, so what downfalls come from burning green wood?

also how much bigger should the enclosure be compared to the furnace, if losing heat is the problem then i guess a foot and a half around the entire furnace and filled with.... fiberglass? no something else....

For a fan forced system like this you don't need a big heater.
I don't have the Canadian winters but back in DE we got it down to minus 20° Fahrenheit.
Our place to work on the cars was an old cow shed for milking, about 30m long, 8m wide and 3m high.
To heat the place we used a beer keg as the actual oven part, cut a door and hole for the furnace to complete.

Around the keg was a 200l steel drum that previously had oil in it, not the best choice but it was free.

We placed the drum so a cut out cut be welded around the door in the keg-

easiest way to seperate the high air flow from the heating from the needed low air supple for the oven.

The flu went through the drum into the keg, for an easy push fit we welded a suitable ring over the hole in the keg to hold the flu in place.

Two more holes in the back of the drum to connect the "shed" with it and one inline fan to get going.

Only the ouside of the drum was lined with rock wool to provide insulation, the inside was left empty to allow a good air flow.

Total cost at that time was 15 bucks for the fan, 20 for the used keg and a drive to the local tip to collect some pipes for flu and connections to the inside.
Fresh wood won't burn properly but if you pile it up on your shed wall and make sure it stays dry you can get it dry in a few weeks.
If you run out of wood make a second door for the keg to hold a good sized gas or oil burner ;)

Okay, so basically ill have a plywood compartment with the furnace in the middle, the chimney leading out the top, the whole thing lined with fiberglass and something on the fiberglass to keep it from burning, a door to access the whole thing, a fan facing the furnace and pulling air from the workspace, blowing onto the furnace, and ducts leading back into the workshop with hot air.

Sounds like all I need now is a cord of wood, Haha.

my only question is where would be the best place to put the ducts, with a fan the size I have it will heat up the entire place in minutes. but keeping it heated will be the problem.

How much oil will it take to keep the place heated for a few weeks? I have some used engine oil, probably not the best idea but it will work...Right? just pour it on some hot coals, close the furnace door and open up the flu. Heating done for a half an hour, mmmmm, I can smell the cancer already! Of course I'm kidding, but I've never worked with oil heaters so I could use some insight.

The only other thing I'm questioning is how to keep the ground warm, its on a patch of solid ground that's mostly clay, and has about an inch thick of gravel on it, if I insulate the ground lining properly, is it possible to keep the ground warm and free of permafrost?

For going oil it would be best to talk to a local heating guy and ask for an old oil heater to salvage the parts.

I would not use wood for the oven cover as it can get damn hot in case the fan is not running, playwood could start to ignite, that's why we used an old drum.

Don't line with fibreglass, use rock wool or glass wool instead, you can get some leftover peices at building sites.

The floor will be you biggest problem and might need some pallets with carpet on it to keep it warm otherwise it will take several hour to warm the floor.

The wood furnace i have is a whole furnace with casing around the center burn barrel, a stand, a door, and a flu, the whole package. from what you said, it just needs to be contained so heat doesn't escape, so im going to make a little compartment to shield it from the outside, made from plywood and lined with glass wool (I call it fiberglass).

The door i described was on the outside of this compartment so can access the entire thing and close it when im inside. what im thinking of is something to line the fiberglass with so im not blowing fiberglass into the air and breathing that in. Also is a duct fan a good fan for this or would i need a bigger one. perhaps a modified house fan?

For the floor I will probably be wearing shoes most of the time, but I just did some research and those gym styrofoam padding squares might be the answer. they are solid, heat absorbant, comfortable to walk on, and cheap! at 3$a square meter, you cant go wrong. Ill just fill in the cracks with spray foam or some other kind of soft filling. and im off to the races!

Thanks for the help none the less. ill try and get pictures up as soon as i can. I'm waiting on a new camera. my current one has the quality of a potato. :P.

Fan depends on the heat the oven can produce.

I think a small desktop fan with 3 speed settings inside the duct or in a housing would enough for the start.
An inline fan is good if it can fit into the pipe you use to connect to the shed, but you should check how much air they can deliver and if a dimmer can be used to adjust the speed.

I have a couple of computer fans. I'll wire some of them up to an old PSU and bob's Your uncle. If not then I'll find some way to blow heat for the whole thing. I'm probably thinking too far ahead, I've got the frame built and I'm waiting on more cement board, but I'm thinking of using it just for the parts that will have heat on them constantly (like the back with the furnace) and plywood for the rest. Until i have the whole thing built with the barebones, I'm going to use the K.I.S.S method.

later on in the year (when i have money), i'm going to lay down some thin copper tubing under the mats and have the furnace heat water in a tank and send it through the pipes with a little pump. Because its going to be expensive I'm saving that plan for the -50 days!

But once I have the entire thing built I'll be able to make and post instructables! Thats my entire plan :) Thanks for the help! Cheers!

If you want to upgrade the whole shed anyway check if you can get leftover pieces for freezer house walls.

They are basically a thick layer of insulating foam with a sheet of aluminium or steel on each side.

If you don't mind some "patchwork" it is very cheap way to get very good insulation, just fill the gaps with expandafoam and if you wet the surfaces it will even "glue" the sheets together - cut off the excess once cured.

Most important however is to check for drafts.

We used colored smoke bombs, the kind for the boat and fired them in the closed shed.

Everwhere we could see big amounts of smoke coming out we fix it while smoking with foam.

You won't believe how many massive holes a seemingly closed shed can have LOL.

And at minus 50 even a slight breeze will remove the warm air really quick.

Patchwork is the plan for now, sprayfoam sure is a beautiful thing :) next weekend is the time to be doing it hopefully. my friends might come and help me get the whole thing up. it'll take us two whole days but it's gonna be worth it!

That smoke bomb idea is genius as well, but because potassium nitrate is illegal in Canada, it might be a task that will take a couple of days, because ill have to make it from ammonium nitrate and potassium chloride. and getting it coloured is even more difficult.

The doors are going to be simple sliding pieces of plywood that slide into a seal with handles on both sides and a simple lock to keep it in place. Thats where most of the smoke will escape and im trying to think of how to seal it. Because we get more than light breezes here, try wind above and around 80km. for five months of the year. your in Australia right? well were like your same dry climate just 70 times as cold. :\

Sealing up corners with just sprayfoam seems a bit.... unfinished, what else makes a corner a sealed corner? weather barrier? it doesent seem entirely necessary, but if it needs it then I'll just use tuck tape. if not then just sprayfoam? what else would be good? because if sprayfoam works well alone then i wont have to upgrade.

You can color the smoke with organic Indigo powder, dirst cheap in Indian grocery stores and online, but white smoke works too.
If you don't like the look of foam in the corners get some plasterboard corners, usually for the ceiling but they work great in vertical corners as well.

I'm kinda penny pinching right now, so spray foam it is! lol.

thanks for the help, and if you have any projects that you need info on, ask me and ill see if i can be of any help, because lets face it... i owe you one!