Mike VanKanan

Thanks Kenneth

I have a better idea of what you are talking about, I probably have used them before.

I was worried about asymmetrical forces acting on the green house from loading the north and south differently. That's something to worry about. I'm over my head with this. My gut tells me that I could do this and it would work. If it was my place I might do it. As soon as you get into any engineering though it gets more complicated. Tom would have to convince the town this isn't a pennant structure, or it would have to be code, 50-90 psi/sf load. The idea is falling apart in this form.

About rock wool, that's outside the poly right. It would nice if I could use it on the inside against the poly. Be nice if there was bendable XPS foam. But even insulation inside the poly would, as you said, probably result in uneven snow loading because less heat loss on one side.

Thanks again.

 

Hi Gilbert

This might help you, They have about 1200 gal of water they worked with.

https://www.builditsolar.com/Projects/Sunspace/LowCostHtStorageNathan.pdf

Mike

Thanks Kenneth

When you speak of two hole strap I'm not sure of what you mean, I'm familiar with the multi holed strapping. That would be faster, your talking about those self driving screws?

Thanks Mike

Thanks Kenneth

Mike, “Shrink makes a stink”? I’m not that old...I’ll guess it’s about the river?

The shrink wanted to subdivide and develop some property, He was stopped, his land however was still zoned agriculture so he got some hogs...........and then he got his permit to develop! I think it made the NYT?

I'd like to meet David the guy in the Video.

At a 40 degree delta I lose about 1.5 million btu's out the glazing and 200 thousand out the north side with 2" XPS

Kenneth "I agree the hardware can get expensive, so is labor. Bolt + nut, drill holes, hammer bolts in, tightening nuts... a lot slower than wood screws and a driver. "

You'd bolt those clamps you spoke of? Drilling is hard so I'm rethinking that. I wonder if I could get 300-400 pieces of flat 1" galvanized stock cut and drilled, I could then bolt them to the 2x4 on top of the rib?

Kenneth "The beam, where I had said to place it, would cantilever the new roof (sort of, since it isn’t a stand alone structure, just shoring the GH frame) Remember you are just adding nailing surface for insulation and roofing, not building a structural system. That’s already there in the GH frame, you just want to ensure that it can take the additional roofing load plus a one-sided (rather than evenly distributed) snow load".

They do come down I've talked to folks with experience, I'm told that they bow out at the ground the ribs can twist and bend down or break. 35 lbs/sf snow is about 20". That,s possible. Part of the reason Tom want to do this is so he can take some time off in the winter and travel some. I'm aware that the snow will stay up there with out the heat lose through the glazing.

Kenneth "Then you are almost building a pole barn shed, and maybe that’s easier"?

Yeh" that"s where I think this has to go? I think I need two rows of posts, One where you suggested, and another on the front of the last trough, That would give me spans of 5' 6' and 1' cantilever. The posts in the center are 13' there will be a lot of stress on them, I'd like to keep them as small as possible to save space?

Thanks Mike`




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Thanks Kenneth

Groton huh are you old enough to remember "Shrink makes a stink"? If your up this way I could give you a tour if you want? I'm not committing Tom though.

We have toured Victory Aquaponics. I'm very envious of their curtain system, love to get that contraption that makes it work. I think reducing the heated volume at night is a great way to go. They heat water with that big wood furnace and store it in an insulated tank, and then use that to heat the fish tanks. It's less then 300 gal, talking to the owners made me aware of the amount of heat you need. Lots and lots.

I'm not sure what the rock wool would get me, I haven't dug into what point added r-value pays off with all the heat loss from the glazing. How long would that exposed poly last?

"(using 2-hole straps?)" I'd probably need 300=$$$. Tom uses tech screws, I'd like some idea of what effect bolting or screwing has on the structural integrity, I think not so much but I really don't know technically?

Down and dirty what I'd like to do is get some 18' 2x8 and rip it to 2x4, lay them flat on the bows, I could pre-drill them along with some flat metal strapping, i could bolt through the wood and and the strapping with the bows in between, making a clamp. Save us from all that drilling through metal, and we wouldn't have to worry about the structural integrity. I could then just plumb cut the ends where I needed to meet the north wall, easy to detail the eave. That would eliminate any finagling around the bows. I could then lay the XPS strap that and then the roof?

That would leave exposed wood inside that would get wet from condensation? Any alternatives, I think aluminum would cost to much? Metal studs? If we used painted wood how long would it last?

Posts will be in the way but I don't see away around them, I need two rows I think one at the ridge and another that splits the rafter run. Perhaps I can get by with one row of posts by setting the beam back from the ridge and cantilevering the roof?

thanks for the link  https://www.builditsolar.com/Projects/Sunspace/GreenhouseHX/GreenhouseHX.htm I'll look into it more. Tom has a 16.4 KW system that runs the farm. It's one that feeds the grid surplus. When I first talked to him I misunderstood him and I thought he was banking electric all year? Easy, get a electric hot water heater!

This was interestinghttps://www.youtube.com/watch?v=VPd212q6uvU

Thanks again Mike

Hi these are some other thoughts on Tom's greenhouse, I copied this from a post to another forum, hope it's not confusing.

Some pictures: gb3 shows the end of a grow trough , under it is the 2x12 box  with the PEX water heating tubing. The box has a poly vapor barrier stapled to the bottom, it's supposedly stuffed with fiberglass, with the tubing laid on top. My understanding is that it isn't attached to the 3/4" plywood bottom of the grow trough. In the picture the red tubing connects to the 50' of flexible stainless that was added latter to try to boost the water temp before it returned to the fish tank. The pvc in front of the tank is an air line that feeds air stones, the flexible white pipe is the tank water return. The tank water feed is along the North wall to the left, it's 75 ' of 4" pvc that attaches right against the metal frame.

So the heater loop goes from the boiler, to the stainless steel loop, then down the pex and back to the heater. It works if you want to burn 100+lbs of pellets, his winter daily burn rate..That's 800,000 btu.s if I take 80% (boiler efficiency?) that's 640,000 per day. Using 4500 gals of water that's 37,350 lbs. That should raise the water 17 degrees I think? We dump air on a sunny winter day so the water would be gaining heat for a time and it would have a pretty small delta for some more of the time. So most of the loss would be night. Grow lights are on for a couple of hrs morning and night so the are also contributing some more heat. The oil fired furnace kicks on at 45, I think he ran it hotter last year? Tom use 200 gal/3 weeks = 9.5 per day x 139,000 = 1.320,500 btus  80% of that is another 1,056,400 btus a day.   I haven't done any calculations for the water heat loss to the green house interior. I did calculate the greenhouse heat loss at 3,360,000 for 24 hrs with a 40 degree delta. There is about 2,700,000 btu's of sun light hitting the green house. These aren't very accurate numbers I'm using 1500 btu's/sf  it's kind of an average out of a book for 40% latitude Oct- Mar and I'm at 42, I used 30 degrees for the entire surface, The calculus of that curve is way beyond me, I'd love to learn though! Almost got pictures down.......maybe?

I'm not sure what to make of all these numbers they are informed guesses really? I think we should insulate all the water and piping we can. I think we should reinstall or replace the heat exchanger plumbing directly into the grow troughs. I'd like to capture as much day time heat as we can at least into the aqponics system and any extra into some kind of storage.

Some ideas I'd like to explore are cheap irrigation tubing on metal collectors, I could get 1000' hanging off the north side of the greenhouse interior.

I'd like to explore pulling air through some auto radiators in the top of the greenhouse into a coil of some kind in water, Seems that another radiator in water would work as a heat exchanger? Don't know how good that would be for the radiator under water?

I'd also like to try to blow air through a pipe in the trough (4"?), if it works that might be the simplest?

Anyone think blowing air through water might increase heat transfer? You could get about 500 pieces of 1/2" irrigation tubing  in a 30" diameter barrel top. If you had a bunch of tubes submerged into 3' of water, how much air pressure would it take to blow air out the bottom of the tubes?

Mike

Mike I like your design. Many years ago I played around with the idea of trusses like that with a foot of cellulose blown in them.

Sure is a lot to read, that's a big thread. Better get to reading.

I'm interested to see how your composting works out. Tom has free goat bedding delivered from next door. I had a hard time getting any solid information about potential heat. Tom's not so thrilled about compost, he thinks it's harder than you think! He's a farmer/science teacher it got to work and not take to much time. I don't know enough about keeping it working. I just thought the physical build bins, insulation, heat exchangers, could be fairly robust, load it once in the fall with a tractor? I think you would need some gigantic pile but I really don't know.
 
Mike

Hi Mike
Maybe!

mike:"I hope you don't mind, but can I get some clarification?  Is the current polycarbonate glazing staying in place in the areas you're insulating?  And the insulation would then go on the inside (possibly similar to how you have it now)?"

Right now there is double polyethylene film that's inflated. He would like to put the polycarbonate on the south side and metal roof on the North. We are both 70 so replacing the poly in 6 years will be harder.

mike: :If you could fit the XPS to the North wall/roof AND seal the edges so air can't circulate behind the XPS, I'd think you'd be all set."

If the picture came up you can see what our first attempt looked like, We straightened out the curve, pretty hard to seal that. I never really liked that idea but it's his place.

Thanks

Hi again

I thought I could go back and reply to previous comments and I wanted the picture up while I did it so I ended the last comment.

Thanks Pearl are you anywhere near Zanoni, almost moved there.

Mike the XPS would be exposed to the greenhouse air, in the picture you can see some we hung inside. There are problems with what we did,  I think the condensation between the glazing and the foam would be a problem? There's a better picture coming that might show that better. The greenhouse is full of condensation now the plants float on XPS rafts. Were you worried about condensation affecting the foam?

I think as far as snow the roofing should be vertical, I'd think it would stick more the other way? We are thinking of extending the rafter line out straight until it intersects with a line plumb to the wall. That's a scale drawing so that makes a rafter around 17' so a shed roof with a 17' run Crazy? I think I need some type of beam/header at the ridge and one half way and then some type of post to the ground? Make the addition self supporting, able to carry a couple of feet of wet snow.

The greenhouse gets it's strength from it's shape, that shape must help in wind ? I'm a little worried about that flat roof wanting to lift somehow? There's no real foundation just driven pipe which the hoops sit in and are screwed together.

I wonder if I added enough additional hoops could I do away with the posts?

Thanks got go plant  

T Melville
Thanks, what a surprise, wish it was in English though LOL

Would another hosting service be easier? Anyone else use dropbox?

Mike