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the first wofati greenhouse design

 
steward
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I can't really confirm or deny the math, but if it's accurate and you have 240 lbs of weight spread evenly along a 4' long 3.5" diameter pole, it'll be fine.  Take that same pole and pretend a 240 lb person is hanging from the middle and it will barely deflect.  And that's with a point load at each hand.  Spread out their load and they'd barely bend it.

I'd probably try to aim for the fat end of the poles to be under the heavier parts of the roof.  So probably all the poles would have their butt end into the depth of the wofati.

The 10' span of the purlins may be a bigger concern.  Use fat logs for those
 
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Josiah, have you had a chance to look at the document Julie mentioned? It has some very applicable data, at least if the species are comparable to what you have there at Wheaton Lab. The Montana Fish and Wildlife website indicates the predominant species of tree is either Douglass fir or Ponderosa pine, I believe they are typically considered to be slightly stronger than the spruce listed in that document. The numbers I saw seem to confirm Mike's comment that the beams and rafters are a bigger concern than the actual 3.5" roof poles.
 
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Dez posted these great pictures of the greenhouse build in his Bootcamp thread. I don't know if anyone spotted them there, so I wanted to make sure you saw how it's coming along. It's super exciting to me!





Am I right in assuming that these are the posts surrounding the trench area, where I drew the lady standing?



 
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Could you please point me toward the discussion on how the thermal wells were installed? I'd like to try putting in a thermal well and setting a water tank on top to prevent freezing in the winter. Thanks!
 
steward
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You mean this?  https://permies.com/wiki/145105/wofati-greenhouse-design-build-raw

 
Mary Combs
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Yes - thank you - one of the videos has an explanation that you used an excavator - dug out a platform for the excavator at the depth its arm extends to and then dug the rest of the depth from that platform. I have an excavator - though I'm not sure the maximum depth it will dig. I'm also not sure I have 30+ feet of cover - but it would be a fun fact to discover when I have the time to try out this technique. I was hoping you had some clever method of drilling a hole to set the casing into, without the expense of a well drilling company. if it is just a matter of digging it in, that's within our capabilities. Its just that disturbing that much ground will create a mess that will take at least a year to settle - and the area around a water tank is going to potentially stay sloppy for a lot longer once the ground is disturbed. I'm interested in any other thoughts you might have on this application of a thermal well.
 
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Are the live zoom discussions being recorded?

If yes, is there a thread with a listing for them?

I'm unable to attend the live zooms but would like to follow along as I'm hoping to be able to build a similar structure this November. A single resource with all the relevant designs, plans, discussion threads, zooms, would be wonderful.
 
pollinator
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They're being recorded for the movie, not sure if they're planning on releasing them in their entirely
 
paul wheaton
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We do a zoom thing 3 times per week.  All 3 are recorded so taht bits might make it into the final movie.  The friday sessions are posted cuz that was what we offered to the kickstarter backers at $50 and up.
 
paul wheaton
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I was hoping you had some clever method of drilling a hole to set the casing into, without the expense of a well drilling company.



We've talked about this quite a few times.  We think we can make a hole about six feet deep with our electric auger.   And there are some ways of making holes by hand that are super slow.  We are open to more ideas.  

Here's a possible idea:  https://permies.com/t/54084/permaculture-projects/Digging-extendable-post-hole-auger

So - put a tall post in the ground next to the hole, or maybe set up a tripod.  Maybe something could be dug 20 feet deep in a few hours.

 
paul wheaton
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From dez's thread:

 
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I haven't seen a suggestion for this with the search function, but I thought it might be at least an interesting discussion to bring up. Would it be worth the while to apply a thermal barrier to the inside of the greenhouse?

I was researching a ghillie suit that was made to thwart infrared imaging.  It had a super-cheap, DIY way to make thermal barrier. You spray glue two sides of bubble wrap together, with the bubble sides facing each other, then you spray glue emergency blankets to both sides of the bubble wrap, making a bubble wrap-space blanket sandwich.  It struck me as a pretty cheap way to make something with abundant materials (space blankets are fairly cheap; like a dollar each, maybe less if you buy a lot of them). And it seemed to work pretty well for him.

So I was wondering if I could apply it to an empty shed and skimp on putting up insulation and drywall.  I found that thermal barrier is to be used mainly in conjunction with insulation, but it's usually used in the attic to reflect heat back out when the sun beats on the roof, and to reflect heat rising back down and away from the barrier.

What sayest thou?
Thermal-barrier-for-Greenhouse.png
bad drawing by dork
bad drawing by dork
 
pollinator
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Just found a bit about greenhouses from the original horse Bill Mollison--he talks about growing stuff you'd have to import that would cost lots of land and labor for people elsewhere: ginger, coffee, tea, pineapples, cinnamon, vanilla (and I'd add chocolate).  He was suggesting sinking the first story of a 2-story greenhouse, but  the editor of the pamphlets wrote this: ". . .beware of severe thermal stratification problems in 2- story greenhouses. One story with dwarfs performs much better. --DH]"  In case this is relevant.  page 92 of the pdf document "Introduction to Permaculture", the PDC Mollison gave in New Hampshire.
 
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