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.

 

 

[k edmonds]

Hi Cliff,

Congratulations on obtaining a greenhouse.  I am a home builder that uses insulated concrete forms(ICF).  These blocks look like large lego blocks that stack and then are filled with concrete.  There are many local and national manufacturers of ICF blocks, but they generally accomplish the same thing when installed and that is provide a well insulated wall or foundation that keeps the cold out and the heat in.  Most blocks have a real R-value of around 22, but when you factor the thermal conductivity into the equation the effective R-value goes to around 38-40.  At the very least, if you can place your footing below the frost line for your area and then install ICF block up for the foundation wall you will keep a lot of cold from coming in from the surrounding soil.  To go a step further, the interior of the foundation wall could be excavated.  Installing insulation and hydronic tubing at the bottom.  Then back fill with compacted sand.  This provides a bed to "wick" heat out of the hydronic tubing.  This works well with solar water heating.  You would start running solar heated water through the system probably in August/September to start "banking" heat for the coldest months and then run the system through out the winter.  You may have to have some supplemental heat but it should be minimal. 

I have talked about this type of system before on the site so I hope I am not boring anyone, I am just a true believer in the ICF construction process and how it can benefit all of us in the AP world.

Good luck with your project.

Kip

[Linda Logan]

I don't have construction experience that I have done myself but here are a few suggestions.  Make your north wall painted wood (flat titanium).  For the roof and side walls there is a product from Germany that has better light transmission than glass and lasts forever - called F-Clear.

You might consider going into the ground for your foundation and doing some insulating and then heating that ground from a rocket stove or something else.  I understand there is a man in Colorado who keeps his greenhouse at 70 when there is snow outside.  I know there are people on this list who could give you specific materials and how-to's

Have fun

[Jim Fisk]

Hey Cliff,

I have about the same climate as you (been snowing and 20's for 4 days now here in the mtns. and almost April?) and I got this link off of our forum here and it is the best I have seen on GH sustainability.  Only crit I have of it is they should extend the heat draw tube system so that it pulls from near the ceiling rather than GH floor (you know, where the heat collects:-). That would make it even more efficient. That jumped right off the page for me but the concept is spot on:

http://www.sunnyjohn.com/photos/greenhouses/grnhs_woodland_gardens/...

I will be digging up at least part of my GH floor (still dirt) to do this myself (not under the GBs and FTs that are already in place). The black tubing is pretty cheap and has a huge pay back used this way. Dries out the air in the GH as well which is real important.

As to cover I designed my GH with an insulated and limited light North side for the fish room (metal roof with a white or clear panel every 3rd one and well insulated board and batten wood walls) and polycarb for hot house side with a 4 mil poly double layer inside for insulation. I separated the 2 rooms with an insulated wall for 2 heat zones as I raise Trout and they like it cold.

With that and my woodstove that also heats the sump water next Winter should be a breeze. Remember that the system water (in my case 2000 gal) is also a huge heat sink as well. I made it thru our first Winter with 4 mil poly, tarps and my own woodstove design that keeps it in the 50s during 12F weather for 8 -12 hrs between loads and is all automated and monitored from the house. So far loving it but we are well equipped to handle wood heat here and have our own trees for fuel. You know, a farm

[Jon Nose]

ran across this greenhouse glazing on the weekend has a R 2.3 rating on the 5mm which is higher than double glazed windows ...cdn site but they import from the US

http://greenhousecreations.ca/upload/RC-GHC-Benefits%20of%20Solexx.pdf

http://www.greenhousecreations.ca/solexxtrade-glazing.html

http://www.solexx.com/why-solexx.html

[Vlad Jovanovic]

Holy molar, those are some impressive numbers Jon..My first thought was "yeah, but how long will the stuff last before yellowing, turning brittle due to UV radiation etc...I opened some of their PDF's and saw a 10 year warrantee, with even longer life expectancy...Now I believe that every company somewhat inflates their numbers for marketing blabla, my brain automatically subtracts about 15%- 20% of whatever it is I'm looking at right off the bat...But if this product is even close to what they claim...that's pretty darn cool

Their greenhouses and cold frames are pretty ridiculously priced IMO, but heck you could construct the frame/skeleton yourself...but I'm not seeing a price on just the GH cover material itself...only complete kits

Jon Nose said:

ran across this greenhouse glazing on the weekend has a R 2.3 rating on the 5mm which is higher than double glazed windows ...cdn site but they import from the US

http://greenhousecreations.ca/upload/RC-GHC-Benefits%20of%20Solexx.pdf

http://www.greenhousecreations.ca/solexxtrade-glazing.html

http://www.solexx.com/why-solexx.html

[Jon Nose]

Got quoted about 3000 for 900 lineal feet but depending on quantity they will go as low as .99 square foot .. but might look at importing direct from MFG and see if i can get a better price ..or if enough of us are interested buy in bulk ? Dealer did mention that they know of some lasting 20 years .. but again they are trying to make a sell.

[Cliff Dillon]

Thanks for all the great advice.  As far as the foundation goes, I should have specified in my early post, I am planning on building the foundation below the frost line.  I like the idea of using the ICFs and the using the hydronic tubing.  I will have to do some research on pricing that out. 

 

Jon - Funny you mention using Solexx.  I have actually done some pricing on that material.  I don't know if any of you use greenhousemegastore.com but they carry all kinds of panels and films including polycarbs and solexx.  I saw the solexx but had no idea the R values were better than the polycarbs.  I very well may use that instead of the polycarbs for the roof and south facing wall.  The price difference is not that much.

 

I would like to use a cheaper material for the north, east and west walls.  I thought about using wood like you said Linda but I was concerned about heat loss and weathering of the wood.  I also thought about using structural insulated panels SIPs or insulated metal panels.  Has anybody ever used these materials?  I think the heat retention would be better but I'm not sure its worth the added expense. 

 

By the way Linda I googled F-Clear and came up empty.

[Linda Logan]

I always say the wrong word, it is F-clean

here's a link  http://www.f-clean.nl/index.php?pg=about&id=17&lg=en

Cliff Dillon said:

Thanks for all the great advice.  As far as the foundation goes, I should have specified in my early post, I am planning on building the foundation below the frost line.  I like the idea of using the ICFs and the using the hydronic tubing.  I will have to do some research on pricing that out. 

 

Jon - Funny you mention using Solexx.  I have actually done some pricing on that material.  I don't know if any of you use greenhousemegastore.com but they carry all kinds of panels and films including polycarbs and solexx.  I saw the solexx but had no idea the R values were better than the polycarbs.  I very well may use that instead of the polycarbs for the roof and south facing wall.  The price difference is not that much.

 

I would like to use a cheaper material for the north, east and west walls.  I thought about using wood like you said Linda but I was concerned about heat loss and weathering of the wood.  I also thought about using structural insulated panels SIPs or insulated metal panels.  Has anybody ever used these materials?  I think the heat retention would be better but I'm not sure its worth the added expense. 

 

By the way Linda I googled F-Clear and came up empty.

[Jim Fisk]

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.

[Jon Nose]

I put one in last year Jim ...sort of a red neck version ... after most everything else was built .. with  a shovel ...a after thought.. will do differently next time :(

[Jim Fisk]

Yeah Jon, wish I had seen that a year ago myself. I am having thoughts of adding on another 16' section to the GH for a composting, worm bins, more GBs and workshop room. I will do that in there for sure and wherever else I can still fit it in. Nice warm floor all winter maybe. I do love working in the GH, even making siphon orders in there, on cold sunny days.

[Linda Logan]

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.