Insulating a stand alone wood framed greenhouse

Hey permies! I have build a green house out of salvage wood, and windows. Im planning on using the hobbit stove i have to heat it and to heat the water reserve i will have in hot water tanks i have salvaged. The big question i have is what type of insulation would be best? Cost and access to material is top priority. If i was working a job where i had access to waste insulation it wouldnt be a question but i want to keep this project going for years. I just cant find the answers anywhere else so i thought i would ask y'all. Thank you in advance . When i get some pics ill load them up

Full confession, I have built a used windows greenhouse, but it stands unsealed and uninsulated.
I have plans, but no time.
For the roof, alternating layers of plastic and cardboard.
For the back wall, dirt/wood chip infill.

What part are you insulating?
I presume it isn't the glazing.
South facing knee wall?
Northern facing wall ?
Northern sloped roof?
End walls?

I have been experimenting with bubble wrap on my high tunnel.   I am a long way from having conclusive ( or even subjective)  proof that it works.

William, it is wood framed double paned repurposed sliding glass doors for the glazing. Solid north wall and windows on the east and west walls. Sheathed roof on north side with purlins running with the rafters and purlins running perpendicular for attachment. Steel ag panels as the roof. I sheathed it with 1x 6 and wider salvaged from siding pallets. The roof is sheathed from the same as are the walls. I plan on drywall or some panel system to add rigidity and another layer of insulation. My first concern is best R value for the 2x4 walls and 2x6 rafters. I've read rockwool but that is way to high for my budget. Everything has either been salvaged from the job, windows doors framing and pallets, or I have gotten materials half or less off at local lumber yards, metal roof and trims and subfloor. I have some 3 in foam board left but not enough to make any substantial progress except maybe around the windows in the walls. The back wall is 14ft long and 6.5 ft tall. Here in central Illinois they put plastic over the studs before sheetrock. If i do that i would use the plastic wrap from the replacement windows from my job. Unless i can find a jobsite they are throwing out unused pieces of rigid foam im guessing i only have fiberglass as insulation

Have you thought about using hay/straw bales on the north wall?

Anne Miller wrote:Have you thought about using hay/straw bales on the north wall?

If i was working on an unincorporated property i would have considered that option. Oir property is in a small town. Not many rules building with bales might draw questions.

The master plan is to have it finished out nice and tight. using the afore mentioned water tanks for thermal mass plus the small hobbit stove for that extra boost when/if we get very cold temps. I want to grow ginger and tumeric. Not gonna happen in zone 6 without a considerable amount of propane , i know this from a farmer friend who grew ginger for his wife. His wife's happiness may be priceless but tha ginger cost a pretty penny.
It will also help with starting plants for our gardens and market booth.

Why not disguise the straw bales?

That is a really cute building I like the diagonal pattern.

Maybe disguise the bales with a lattice with some veggies vines or flower vines.

Anne Miller wrote:Why not disguise the straw bales?

That is a really cute building I like the diagonal pattern.

Maybe disguise the bales with a lattice with some veggies vines or flower vines.

Well its already framed and sheathed. It wasnt designed for straw bales. The space it sits on is limited. An old patio slab my beds but up to it. Straw bales on the exterior would breed moisture and vermin. While being a wind break it really wouldn't add any r value to the building. Straw bales would also interfere with any water collection and as i said intrude into my beds.

You could do slip straw or some other natural mix of an insulating material and watered down clay.  It's a good R value and cheap.  Basically chopped straw mixed in a wheelbarrow with very watery clay.  Put a temporary form board on the inside surface of the studs and pack the straw in there.  In a day or two when it's dry, move the form up and do more.  

Whatever insulation you use, I'd definitely put plastic to the inside of it to keep the humidity from the greenhouse away from condensing in the insulation.  And tape the joints of the plastic pieces.  If you cover that plastic with something that could rot, you may be well served to put a spacer between them so condensation on the plastic can drip down and not sit against drywall or wood paneling.

Very nice build!
If you can find a place throwing out styrofoam, you could get a lot of r value for free.
Cut it to fit as closely as possible and fill in the spaces left with spray foam.
Even cheaper ,mix it with cob and tamp it it into the wall voids.
Shedded paper can work the same, forming an insulative fibre-adobe.
You could even use flat sheets of cardboard, cut to fit , and sprayed with a borox solution.


I think you should avoid using the drywall, a greenhouse is possibly the worst environment for that material.
If you use salvaged wood like you have on the outside, it will be way more sturdy and allow you to fill in the studs as you go.

Mike Haasl wrote:You could do slip straw or some other natural mix of an insulating material and watered down clay.  It's a good R value and cheap.  Basically chopped straw mixed in a wheelbarrow with very watery clay.  Put a temporary form board on the inside surface of the studs and pack the straw in there.  In a day or two when it's dry, move the form up and do more.  

Whatever insulation you use, I'd definitely put plastic to the inside of it to keep the humidity from the greenhouse away from condensing in the insulation.  And tape the joints of the plastic pieces.  If you cover that plastic with something that could rot, you may be well served to put a spacer between them so condensation on the plastic can drip down and not sit against drywall or wood paneling.

So i have been looking for clay in my area. Guess being in the deep black dirt lands makes it difficult to source straight clay in my area in bulk. Im left with clay like they use for ceramics. Ive been looking for amounts of clay to straw. Do you know how much clay to use for doing the light clay straw mix? I have a 14ft x 6.5ft x3. 5inch wall so 319 cubic ft of material needed. Any leads in recipes will help be it a website or book. Thank you

I don't personally but I bet the google would know

I can't give numerical quantities, but light straw-clay is typically chopped straw barely wetted with clayey water. I expect a 25 pound bag of the cheapest generic clay from a ceramic supply store would go a long way. You would want to cut it into bits and soak and stir to get it smooth and watery. A 25 pound block will make dozens of gallons of straw-wetting liquid. Experiment with small batches to get a feel for ratios.

A pottery studio will have a recycle bucket where waste clay and slop is kept to settle out and be reclaimed. A few buckets of that fresh and unprocessed may be free or nearly so, and reduce your work to prepare it.

Glenn Herbert wrote:I can't give numerical quantities, but light straw-clay is typically chopped straw barely wetted with clayey water. I expect a 25 pound bag of the cheapest generic clay from a ceramic supply store would go a long way. You would want to cut it into bits and soak and stir to get it smooth and watery. A 25 pound block will make dozens of gallons of straw-wetting liquid. Experiment with small batches to get a feel for ratios.

A pottery studio will have a recycle bucket where waste clay and slop is kept to settle out and be reclaimed. A few buckets of that fresh and unprocessed may be free or nearly so, and reduce your work to prepare it.

The issue i see using stare clay slip is that putting it against wood framing and sheathing would cause problems. Unless i wrap the framing with roofing felt i dont think i would be sure i wasnt ruing my wood. Also beings that it is now winter there isnt enough heat and low humidity to dry out the slip. I may put that idea on a back burner for another project, there is always another project.

Yes, winter is not a good time to do LSC. In warm dry weather, I would not worry about wood framing or sheathing. Clay that is kept dry after drying out will not affect wood touching it; posts and door/window framing and lintels are commonly built directly into cob walls.

This thread and this season redirected my attention to my own greenhouse, so thank you!
I will be removing the inside paneling and cladding the outside instead, so I can fill the wall cavities in lifts of 3.5" at a time.

If you were to put in a wood fired heater, even temporary, it could make working with light clay straw feasible.
You could even heat the water used in the clay slip.


As for clay, what about unscented cat litter or oil adsorbent?
The kaolin clays are not great for rocket stoves , because of shrinking but they might be fine for light clay straw .
I'm gonna use the dirt from the floor, but my soul is in fact veryl clay heavy.