Korey Klug

Hi thanks for all the advice, I am using cement block for the thermal mass air duct (exhaust) which has 2- 4 3/4" square holes for the exhaust. I had planed on having the cement block raise about 2-3" in about 7'. I'm using cutout foam insulated door pieces to lay down to keep the frost from cooling the block and mass. The height of the riser is 20" from the bottom of the burn tunnel. The burn tunnel is 1/4" thick 4" square tube which I questioned if it would have enough flow. The 20# propane tank is somewhat sealed and I can shut the flap on the intake causing the fire to smother out, when I open the lid I close the intake feed first and only a little puff of smoke comes out. Once opened you can see it draw in to the burn tunnel and hopefully putting it together doesn't change that. I had planned on lining the block at least the top and sides by bending a long strip of sheet metal into a channel for better flow. I planned on setting it up this week end and doing a trial run before I cob it in. If the flow isn't enough I can cut out another hole and weld another burn tunnel above the one I have which, i figured more smoke and gasses might enter the insulated riser just above the flame causing a secondary burn off of the gasses in the riser and 30 gal barrel. I have little investment into this project so far just some perlite and cement and mortar that I did not have already. I have a large portable tow behind cement mixer which will be handy with this build. The greenhouse is only 10' x 15' in size and I would like to grow in there all year if I could. I am adding some pictures of where I'm placing it in the greenhouse, having a limit on space I tried to keep it small. Being from Michigan and not wanting to feed a fire constantly I figured the propane tank would give me more space for wood (fuel) and possibly a more controlled burn. The pictures I am attaching should give you a better understanding of what I'm trying to do. I now am planning on getting the ceramic fiber blanket insulation for insulating the riser stack if I can find it before Sunday. Again Thanks for any advice.

I built this rocket stove for our greenhouse and then discovered this forum once the welding was done. I used all scrap stuff I had laying around from building stoves in the past. After reading that steel will not hold up to the heat I have looked high and low for cheap fire brick and the only ones I have found are $17 each, which I would have to order. I have fired up my build and the draft seems fine. The main fire pot is a old propane tank which I wanted to have more area for the wood so it might burn longer and the stack is thick walled 8" which I plan on using cob and perlite to insulate it. I have decided to install it in our greenhouse anyways since the temps are dropping down to 40 deg at night and in the 50's during the day. I guess using steel is not the best option but it's what I have and the exhaust is going to flow through cement block which is laid along the back wall on insulated panels and sand base. I have the block on a slight slope and the exhaust will flow through the two holes in the block which is 4 3/4" square holes. I'm using a 8" stack that's welded to the stove and a 30 gal barrel instead of 55 gal and a 5' rise on the 8" chimney out of the wall at the top of the greenhouse. My exhaust will run about 25' total with 4 elbows. My question is which is, is just sticking the pipe through the wall ok, or should I add another elbow and have the stack above the roof? My test run to see if the flow works through the block will be this weekend. Hopefully all goes well and not many modifications will need to be made. Here is a link to a YouTube video I made last night when I fired it up to check it out. Any advice is welcome.