Building a long but narrow greenhouse

Boy, am I glad I found this site. I live in England & there's not much info on RMS' over here. I'm building a long greenhouse against an existing wall & I want to use a RMS to heat it. I have attached a drawing from which you can see the barrel is outside the greenhouse in the open air. I'm currently trying to bid, on Ebay, for a 9mtr length of old chimney flue liner to use as my pipe, but failing that I was going to build a brick tunnel with a slabbed top.

Questions:
I was going to use a 5" uPVC exhaust pipe at the far end of the system, is this ok?
Rather than cob over the exhaust pipe or brickwork I was going to use layers of sand, grit, earth. Is this ok? OR// I could even slab over the top with patio slabs, giving a nice working surface.
As the barrel is open to the elements I thought it would be better to render the fire pit/barrel chamber with a grit/cement coating rather than cob.

Some advice/pointers would be great from you experienced guys

Howdy Ian, I guess my first question would be why you would put the stove outside of the green house? Seems that you would be loosing a lot of heat to the outside air.

Hi, well the reason I'm doing this is because the greenhouse is very narrow ie only 500mm. It's more like a long coldframe [ie I don't stand in it], although it is 6' tall. So, I thought putting the barrel inside [assuming there was enough room] would probably melt the polycarbonate & the plants!

Hello Ian,

Don't know if you got any answers to you question. To be honest I am in the process of building my first rocket stove and oddly enough i too want to heat a green house. This is what i keep hearing over and over do a test run on your creation. I looked up Upvc and it says heat resistant, maybe you can find the specks on this material. I would have to run the stove and see what the output heat is at the barrel. It might be you need 10 or so feet of a non plastic material and then switch to the upvc. Do you plan on digging a trench in your green house and burying the pipe to heat the soil? I'm understanding that 40 feet might be the limit did you say what size rocket heater you are building 6" or 8" I'm going to think the longer the run the bigger the size.



Still new to this hope some of it helps.

Fred

Hi Ian and Fred,
I can see why Ian wants to do the barrel outside - one of the few cases where I'd consider that idea. It will lose a lot of heat that way; if possible I'd put a shelter around it as you don't want the fire (or its keeper) drowning in the rain and snow. And there are lots of uses for a warm shelter.

As for exhaust - one of the common problems with these heaters, especially in greenhouses where the orientation is pretty exposed, is that they do need a fairly conventional chimney exhaust (straight up through the greenhouse works great; patching in a piece of tin to cover where you remove the poylcarbonate is not terribly hard). Or they need some observant problem-solving about wind protection, and the exhaust as high up the building as you can get it. (In a warm bubble like a greenhouse or home, the air inside is trying to rise through any leaks or vents; and cool air is coming in down low to replace it. This means any hole down low becomes a de facto air intake.)

Temperature once you've gone a few meters under a damp garden bed should be pretty low, like 25 to 50 C, maybe 100 C if it's a super-short bed. I tend to prefer a metal exhaust chimney that can be 'primed' with another heat source if needed, but temperatures don't require stovepipe. Just make sure any exhaust is smooth, and the proper size.

I would not recommend using Portland cement for the stove; it will trap damp, and probably crack with thermal expansion. Refractory cement might work but you could still have the damp problem; and refractory clay or just plain clay-sand mortar works great when protected. I would put a roof over this area, allow about 3 feet (1 M) on each side of the hot barrel, and use it as a mud-room or drying room. About half your heat is going to come off that barrel; it might even be useful to enclose the 'furnace room' (with plenty of outside air ventilation) and use a fan to blow excess warm air either into the greenhouse or into the main house.

Yours,
Erica W

Hi All : I created the forum thread 'Rocket stoves in greenhouses' for self-identified members, this will give 'our' group their own forum thread - 'Rocket stoves in Greenhouses', check in, check often Allen L.