Insulating material for greenhouse construction

[Cliff Dillon]

Over the winter I purchased a used steel framed greenhouse.  It is 45' x 15' with 8' side walls and a peak height of 17'.  I am planning on constructing the greenhouse this spring.  It will be south facing and have a concrete foundation.  I am trying to decide what material to use on the sidewalls and the roof.  I want it to be well insulated because winter temepratures are routinely around 20F with lows around 0F.  IT also has to be well ventilated for summer temperatures reaching 90-100F.  I am considering using polycarbonate panels for the south facing wall and the roof to let the light and heat in.  I was thinking of using a better insulated material for the north east and west walls.  Does anyone with construction experience have any suggestions on what kind of insulated material to use.  I have not purchased any of the building material yet (other than the frame) so I am open to any suggestions.  I would like to keep the costs down but I am more concerned using the best materials to regulate the temps easier and limit my heating bills.

 

FYI the concrete foundation has not been built yet either so if anyone has any suggestions about insulating a concrete foundation I would appreciate the info.

 

 

[Jon Nose]

Linda a short and easy explanation  ... you suck the hot air in the greenhouse with a fan that pushes in to big O (drain tile) that is buried in the ground Three layers high .. it removes the heat and returns cool air to the greenhouse ... at the same time it stores the heat for winter time when you need it . some of my pics here...

http://community.theaquaponicsource.com/photo/albums/thermo-heating...

[Linda Logan]

In the winter there is sufficient heat in your ground tubes to warm the air.  I thought you needed to add heat into the ground tubes in the winter to create a warm atmosphere.  I appreciate your discussion of this.

Jon Nose said:

Linda a short and easy explanation  ... you suck the hot air in the greenhouse with a fan that pushes in to big O (drain tile) that is buried in the ground Three layers high .. it removes the heat and returns cool air to the greenhouse ... at the same time it stores the heat for winter time when you need it . some of my pics here...

http://community.theaquaponicsource.com/photo/albums/thermo-heating...

[Jim Fisk]

Linda, here is the link again. Go straight to the source and learn from them.

woodland_gardens/...

[Jon Nose]

Hey Jim can you point me to the info about how they pull the air from the bottom as opposed from the top ? I ran mine last year pulling air from the top and was not that impressed with the results.. guess I may have been running it the wrong way.

Jim Fisk said:

Anyone find a good deal on ETFE. Friendly AP swears by it and they have the prettiest GH I have seen to date:

http://www.friendlyaquaponics.com/farmers-greenhouse/

Also, has anyone here done the 3 layers of 4" pvc pipe subfloor heat storage I mentioned above? Here is their plan with all of their info attached so I don't think I am breaking any rules by posting it: I posted the link above.

Like I said above I don't understand why they don't pull the hot air off the roof area as that is where the heat is. Other tan that it is a great idea worth thinking about especially BEFORE the GH is up while the loader is there doing the foundation. Heating and cooling solved.

[Jim Fisk]

Hey Jon, They just go one barrel higher than floor level. Hey, maybe they know something we missed.

[Jon Nose]

Maybe... I will switch it around this weekend and see what the results are .. if nothing else it will answer my question whether I wasted my time or not ... thanks Jim

Oh and one more question .. been going over you stove design and want to take out my rocket stove ( 8 hour burn over 1/2 hour)... (but I would like to keep my exhaust system to absorb the heat that's normally lost up the stove pipe )....how far  do  you estimate you can you can back toward the ground ( ninety degrees down another 90 to the exhaust system  in order  that you still have enough suction that smoke will still exhaust efficiently .

 

[Vlad Jovanovic]

Hi Linda, UACT = Underground Air Circulation Tubing...

Just flexible, usually perforated tubing. Like the 4" perforated polyethylene drainage tubing I, and probably many folks have in their yards. That's all that is.

Linda Logan said:

I'm gathering from the discussion that you all understand this drawing.  I'm having to infer what a UACT bunker is.  Would someone in lay terms give an explanation.

[Jim Fisk]

Hi Jon,

I have yet to build and test an underground rocket stove. Mine is also a wood gas burner but NO WAY can you expect to send hot exhaust down below the stove without smoking yourself right out of the GH unless you add an exhaust blower. Why are you abandoning your RMH? and can you better explain what you mean by "( 8 hour burn over 1/2 hour)"?

My concerns with the RMH is the small fuel area and those cold starts. As efficient as it is there is a concerning limit to how many btus you can produce and store without tending it regularly given such small wood fuel area. Hope I made that clear

From a cold start there must be a frustrating period of smoke in your face. You have to get that short high temp area very hot indeed to drive the hot air down in fact reversing natural heat rise. Now a power vent just to get things going and a larger fuel chamber could change all that I see going against them. Not to stifle your enthusiasm for my design, but perhaps you could make a few changes to your present RMH to make it more practical.??

If you go with mine you should consider enclosing it in a skin and adding a hot air blower that sends clean hot air into your earth mass tubes in the floor. This is what I have in mind along with the excess hot air storage of the GH. Not hard to do.

As to your mass storage I really find it hard to believe that drawing air lower in the GH could possibly be better than off the top hotter area. Have you really done all the massive heat storage that they advocate? It is a major undertaking and not at all cheap but the payback (like so many things) could certainly be worth it if you can afford the time and money up front. I could not have. I'd still be building the GH and would have missed out on all those delicious veggies we enjoyed all this Winter.

Keep in mind that Vlad built his stove based upon my design and he may have some good advice here as well now that he has lived with it for the first Winter. I have added a great deal of automation to mine this Winter in the way of digital T-stat, timer to over ride the T-stat for fast start ups even when the stat is not calling and the same timer to shut it off during filling when the stat is calling. Works fantastic and beats the heck out of plugging this in and unplugging that and then having to stand there until all is ready to switch it all back so I can leave. That got real old. No more.

Hope I answered all.

Jon Nose said:

Maybe... I will switch it around this weekend and see what the results are .. if nothing else it will answer my question whether I wasted my time or not ... thanks Jim

Oh and one more question .. been going over you stove design and want to take out my rocket stove ( 8 hour burn over 1/2 hour)... (but I would like to keep my exhaust system to absorb the heat that's normally lost up the stove pipe )....how far  do  you estimate you can you can back toward the ground ( ninety degrees down another 90 to the exhaust system  in order  that you still have enough suction that smoke will still exhaust efficiently .

 

[Jon Nose]

The longest burn time without feeding the rocket stove is about 1/2 hour ... thought I read some where that you can put some big chunks of wood in your stove design so that you can get 8+ hour burn time without refueling? Don't want to use pellets in it because of the long term costs. I find that even though I can achieve over 850 F degree after a hour or so I still am not getting the air in the green house to warm up. And yeah there has been a few times when  had to open all the doors to let the smoke out .. a small fan blowing into the fire box does solve this issue.

RE: mass storage.

When the sun is out top of the greenhouse last year got to 105 -110 f degrees and even though I put in a larger blower so that the air is exchanged every 3.5 minutes  I still had to add another fan to exhaust out side. The mass heater fan has a sensor that turns it on full blast soon as the peak of the green house hits 90 degrees then  shuts off at 70 degrees.

The air does come out cool from the floor but I am curios now to test to see if blowing air at the top of the greenhouse will work better ... a 15 min job at most to see. Now based on sunny Jims site calculator should have ran about 1500 feet of big O ... but I was only able to do around 900 feet due to having all tanks built already and the rocket stoves mass in the center etc..

Right now have to deal with a Mink that cleaned me out of 130 to 160 talapia which was heart breaking... which I only discovered after getting back from the long weekend . Knocked over the  pump as well so lost about 2000 gallons of water ... 

Jim Fisk said:

Hi Jon,

I have yet to build and test an underground rocket stove. Mine is also a wood gas burner but NO WAY can you expect to send hot exhaust down below the stove without smoking yourself right out of the GH unless you add an exhaust blower. Why are you abandoning your RMH? and can you better explain what you mean by "( 8 hour burn over 1/2 hour)"?

My concerns with the RMH is the small fuel area and those cold starts. As efficient as it is there is a concerning limit to how many btus you can produce and store without tending it regularly given such small wood fuel area. Hope I made that clear

From a cold start there must be a frustrating period of smoke in your face. You have to get that short high temp area very hot indeed to drive the hot air down in fact reversing natural heat rise. Now a power vent just to get things going and a larger fuel chamber could change all that I see going against them. Not to stifle your enthusiasm for my design, but perhaps you could make a few changes to your present RMH to make it more practical.??

If you go with mine you should consider enclosing it in a skin and adding a hot air blower that sends clean hot air into your earth mass tubes in the floor. This is what I have in mind along with the excess hot air storage of the GH. Not hard to do.

As to your mass storage I really find it hard to believe that drawing air lower in the GH could possibly be better than off the top hotter area. Have you really done all the massive heat storage that they advocate? It is a major undertaking and not at all cheap but the payback (like so many things) could certainly be worth it if you can afford the time and money up front. I could not have. I'd still be building the GH and would have missed out on all those delicious veggies we enjoyed all this Winter.

Keep in mind that Vlad built his stove based upon my design and he may have some good advice here as well now that he has lived with it for the first Winter. I have added a great deal of automation to mine this Winter in the way of digital T-stat, timer to over ride the T-stat for fast start ups even when the stat is not calling and the same timer to shut it off during filling when the stat is calling. Works fantastic and beats the heck out of plugging this in and unplugging that and then having to stand there until all is ready to switch it all back so I can leave. That got real old. No more.

Hope I answered all.

Jon Nose said:

Maybe... I will switch it around this weekend and see what the results are .. if nothing else it will answer my question whether I wasted my time or not ... thanks Jim

Oh and one more question .. been going over you stove design and want to take out my rocket stove ( 8 hour burn over 1/2 hour)... (but I would like to keep my exhaust system to absorb the heat that's normally lost up the stove pipe )....how far  do  you estimate you can you can back toward the ground ( ninety degrees down another 90 to the exhaust system  in order  that you still have enough suction that smoke will still exhaust efficiently .

 

[Linda Logan]

Thanks for the clarification.  My question is since I can't go underground, too much infrastructure to change now,  can I pipe off my vertical chimney pipe (don't know the right term here) into the main GH?  I can't get enough heat transfer now from just the stove burning.  Does my question make sense?

thanks

Vlad Jovanovic said:

Hi Linda, UACT = Underground Air Circulation Tubing...

Just flexible, usually perforated tubing. Like the 4" perforated polyethylene drainage tubing I, and probably many folks have in their yards. That's all that is.

Linda Logan said:

I'm gathering from the discussion that you all understand this drawing.  I'm having to infer what a UACT bunker is.  Would someone in lay terms give an explanation.

[Jim Fisk]

Hey Jon,

yeah mine takes a large load of logs and burns, depending on wood type, from 8 - 12 hrs easily. Back in the day I used to put in a 14" dia x 20" long Elm log on hot coals and go for about 4 days on that in 30F weather. A lot depends upon that and wood moisture. I like 1 yr old wood from the wood shed. It will take an entire large arm load of split wood at a time if your a strapping lad. If not, 2. Like any stove the hotter you run it the more efficient it gets. The after burner helps bring that ultimate temp down a peg. When that is running bright red you are lit. The gasses are burning nice and blue. Then there is plenty of travel in the upper barrel for heat transfer so much less is lost up the chimney.

Every thing you confirm about your RMH I have read elsewhere. It would probably make a great pellet stove with an auto feed like my fish feeders. Of course I too don't want to purchase pellets when I have all the wood I need right here. So, I would have to rethink the fuel chamber in order to put up with one.

Jon Nose 4 hours ago The longest burn time without feeding the rocket stove is about 1/2 hour ... thought I read some where that you can put some big chunks of wood in your stove design so that you can get 8+ hour burn time without refueling? Don't want to use pellets in it because of the long term costs. I find that even though I can achieve over 850 F degree after a hour or so I still am not getting the air in the green house to warm up.

[Vlad Jovanovic]

Hi y'all...Linda I'm not sure I understood your set up?

Now, I'm no expert, but a design like the one Sunny John uses has more going on than just 'run of the mill' thermal storage. I'm pretty darn sure that most of the magic happens because he is achieving dew point phase change.

Shooting for just some 'plain 'ol' hot air conduction transfers and expecting to see stellar results...might be like the guys with 1,000 gallons of fish tank water wanting to heat it 15F with a couple of coils of black poly duct taped to a piece of plywood on the roof...

Jon, I'm not sure what your RMH is made out of (metal/brick), or if you can get a propane torch in there to pre heat it a bit...but if you can, that would definitely help with the smoke issues. If using a torch is not practical, than try at least using some sort of "clean" burning liquid fuel (like Zippo fluid)...Just don't go ape shit pouring it in there :) You could pre-soak some of your kindling. The 'smokeless' Zippo fluid should burn off before the wood starts to burn and help 'pre-heat' the RMH at least a bit, hopefully helping with the smoke...

Having to go out to the GH every 30-45 minutes to feed the RMH is exactly why I did not build one. I like Jim's design, and only modified it slightly (nothing major at all, just used beefed up materials and added a 5mm thick 'shelf' above the combustion chamber and back plate that I can stack brick's on for some added thermal mass...again, no major changes.

The whole reason RMH's work the way they do (when they work well)...speaking in terms of design, are the volume ratio's between a) the feed tube, b) the horizontal burn chamber and c) the vertical combustion tube. a+b needs to = c times1.5 (at least) otherwise things smoke a lot and burn less efficiently than they otherwise could (or should). It is these proportions that one must respect which put a damper on ideas like "hey, I'll just build me a big 'ol feed tube for some autonomy and everything will be fine..."

Which is why I went with a design like Jim's...even though 'sustainability hardliners' might call it "cheating" because of the small electric blower such a design uses. But with that huge (volume) of a "feed chamber" it would be difficult to get that 'rocket effect' without one.

Also, if you use a fan, you can greatly (and easily) vary the regime at which the stove heats/burns. With an AC fan just wire in a potentciometer...or whatever you guys in the states call them...rheostat...voltage divider, variable resistor..with DC you have a number of options to vary input voltage as wel)?

This is nice because it's not always -10 degrees outside and you don't always need it working full tilt. I just hacked an 1,800 Watt AC motor/fan from a hair drier and turned it into what it originally started out as...A permanent magnet DC motor. It works just dandy from 6 to 20 volts (so about 3 to 10 Watts or so now). It moves a lot of air, but unfortunately at a pretty low pressure, so I'll be swapping it out before next winter (in reality, it works just fine though...I duct taped off about a third of the inlet side to mitigate some back pressure issues...I just want it to work better is all)...

Jim's stove is pretty awesome, but I have 2,130+ sq feet of GH space to heat...so I run it pretty full tilt when it's brutally cold. So, I can't really get 8 hours of autonomy at those times. More like 2 to 4 hours depending on the type of wood I'm using. It's not like it goes out after 4 hours or anything like that at all...just doesn't burn full blast. But, it is not realistic to expect a stove of that size to heat a 2,100 sq.ft space made from 4mm glass for 12 hours on one load (when it's that cold out...during the day if its warm out I keep the blower off and just keep it 'simmering' with a small load, which will literally last all day...then get it back up to working temp when I need to).

Oh, yeah...that reminds me...Sunny John and his people were finding that they are having issues with pre-mature fan/blower failure. Reason being, in his original design he uses regular low volume "squirrel cage" fans, (like in the diagram Jim posted earlier) and those use shaded pole motors. As it is, those shaded pole motors were feeding air pressure back onto themselves from the exhaust outlets of the SHCS (when all windows and vents were closed)...thereby over-speeding their running speed, and hence drawing more current...which of coarse caused the motors to run much hotter...which caused them to fail pretty quickly. In-line 'duct booster' type fans apparently don't have this problem, so that's what they use now.