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.

 

 

[Paul Phillip Meyer]

So Cliff you didn't end up adding any geo-thermal or ground heat pump system before the concrete? I've been looking at that and the compost mounds, but after speaking with a consultant it seems like you would need a mega mound to produce up to 250k BTU's that I need which is likely in your case too. 

Cliff Dillon said:

ok  Thanks.  I will.   As anxious as I am to get this project finished, I want to do this right even if it means waiting a little longer to pay for a better quality material. At least initially, I will not have supplemental heat for the greenhouse and am hoping if it is built well, I can heat it with just hot compost and maybe a subterranean system of some sort.  I would like to keep the temps above freezing year round.  I don't need to have temps in the 70's or 80's but if I can keep it above freezing I can use it to keep cold weather crops and maybe even winter over some warm weather potted trees. 

[Cliff Dillon]

I have not added any geo thermal yet. The concrete I poured is a footing around the structure but the interior has a dirt floor so I can still add it anytime. I'm curious how you determined the need for 250k BTU's? Are you trying to keep your greenhouse at a higher temp? I'm just trying to keep mine above freezing. I have read several different sources about heating a greenhouse by using just compost. In fact there is a guy in Chicago who owns a greenhouse business. He says he only uses compost. He teaches classes on aquaponics, raising bees, composting ECt and provides food for inner city poor neighborhoods. I haven't had the chance to visit him but plan to this winter.

[Jonathan Kadish NYC AA Chair]

I have been dreaming of a system that incorporates the Jean Pain compost pile method with a large exterior pile of wood chips and manure used to heat the water in a greenhouse system. From what I understand one of these piles can generate as much heat as 7 cords of firewood over a season and it requires no moving parts if you are relying on a thermal siphon.

[Paul Phillip Meyer]

I'm looking into the Pain method but the greenhouse I am interested in is 6000sqft with high ceilings (currently really just a high tunnel) however I'm trying to figure out how to fully insulate it. I might end up doing multiple large compost piles if I can find the wood chips almost free. Getting that much manure and wood chips would require a lot of transportation/big truck. Looks relatively simple. I'll have to see the more I read.

Cliff what is the farm/name of the guy in chicago? I'd be interested in reading up on him.

[Jonathan Kadish NYC AA Chair]

I just had some trees taken down and kept a lot of chips but once I had enough I told the tree service to take them away. They have to pay to dump them and I asked if they give them away to people who ask and indeed they do. I guess the harder part for me is the manure. There is a horse farm not far away... I'll have  to investigate.

I have visited growing power in Milwaukee, I think the have an arm in Chicago as well. His name is Will Allen. 

[Paul Phillip Meyer]

Yes, I know about Will Allen's business.

[Linda Logan]

Look at the size of the manure pile Will Allen has.  It is huge!  Also, horse manure isn't very hot and will be mostly wood chips.  I like the idea of heating with compost but I'm not sure it is a viable idea on a household scale.  Using a rocket stove with pipes going under GH floor seems to be a good way to go.  There is someone in Colorado who has done this and it is working.  I believe he went down 8 feet though.

Winters in cold climates have challenges.  I'm trying to not use so many inputs that the cost of growing is more than just going to the most expensive organic grocery and buying everything there.

I transitions my winter plants from summer too late and so my growth was not established enough to use all the ammonia etc.  I'm now giving away my forty big fat goldfish and getting fewer blue gil.  This is my second year and each season I'm learning more.

If I were to start again I would place fish tank higher that grow beds, put in underground heating and insulate my fish tank much better.  Then transition plants between seasons sooner (which means looking at planting space and being willing to remove some to do this).

I have a friend who is on his 17th iteration of AP.  His system is more flexible than mine but the point is not lost on me.  

Sounds like you are doing good research.

[Paul Phillip Meyer]

It comes down if you are doing it all yourself or hiring a designer. I've been given quotes of $40-80k to do super compost heating (built inside recycled container crates) but I think it's unrealistic as a real farmer. Being in California outsides natural growers could earn more than commercial scale system aquaponic growers. It's an expensive hobby in my opinion and if it is used commercial and figuring out a way to heat everything to maintain a system you really have to get creative. In Virginia winters are moderate. Yesterday it was 32 now todays its high 60's so it's difficult to pinpoint temperature where I am at, however you don't want your fish to die and you want to keep your plants healthy. I'm actually going to go check out a successful high tunnel farmer tomorrow (she just used raised plant beds with soil and drip irrigation). If I did DWC 12" beds of lettuce the water would all freeze this Jan. without heat. 

And on the topic of insulation. You mentioned insulating fish tanks. I've seen people bubble wrap IBC's and add electric water heaters. I'm curious how cold it can get and the heater keeps the water at a stable temperature. I visited The Urban Farming Guys in MO where it's really cold and they used basic heaters in their IBC's and their fish looked fine and full-size and those winters are harsh. 

[Cliff Dillon]

The guy I was talking about is will Allen from growing power.

My greenhouse is quite a bit smaller than yours. It's only 900 sq ft. I have an unlimited supply of wood chips too. My neighbor has a tree service company and dumps on my property. The manure is a little harder to come by but there is a cattle farm not to far from me that I plan on speaking with.

I had not heard of. Jean Pain. I spent all last evening reading about his method and watching u tube videos on it. I may have to experiment with it on a smaller scale.