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| I've built a greenhouse on the side of my barn that's 60' long, 25' wide from the barn face, and comes down from 2' over the barn at a 30 degree slope to 2' above the ground. Picture a big triangle 25x28x14 with the 25 on the ground. I haven't glazed it yet and am considering raising the slope to 50-60. I'd like to raise the slope with a pole structure built into the 30 degree wooden frame and leave it intact(it's very, very sturdy). What I'm worried about is creating too much cubic air space for the roughly 1800 sqft of 2x clear 6mm film glazing to heat(Or for my heaters to economically heat). The back wall is reflective white and theres an enclosed 5000 gallon aquaponic tank painted to absorb heat, however with that high a roof I have a great fear that even with the substantial thermal mass I have it's too large an area to maintain. I made some(to scale) drawings of the possibilities I've come up with. Note that all added front walls are 20'.
A - current setup. 30 degree slope B - 30/60/24. Peak/slope enough to allow full sun on back wall. could make north glazing reflective. I'm worried the peak is too high. C - 60/24. Same concerns as B. D - 30/48/37. Same concerns as C. E - 30/48/7 degree slope with front partition, 7 degree North glazing. Worried the 7 won't have adequate rain/snow shedding. F - 48/12. Same concerns as D. Any help would be appreciated! I'm fairly stumped! |
Follow-Up Postings:
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| A few questions. What's the extra height add that is of benefit, taller crops? Are you concerned about snow load? Some new designs won't shed snow well. The taller designs will require somewhat more heat but not a night and day difference. There are heating calculators that will answer how much more. Personnally I'd stick with what you have unless you want trees in the whole thing. It will be easier to cover. Only D is a real improvement for snow shedding. |
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- Posted by Cole_Robbie none (My Page) on Mon, Nov 26, 12 at 12:08
| The barn has a separate rain gutter, right? I wouldn't want the dirty water from the barn roof running over my new greenhouse. Also make sure it's not possible for a large chunk of snow or ice to slide off the barn roof and hit the greenhouse. |
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- Posted by BiologyBomber none (My Page) on Tue, Jan 15, 13 at 8:47
| The extra height is intended to let the 13' back wall be fully enclosed in the greenhouse so it would reflect light throughout as well as retain/release solar heat. I've since done the heating calculations and I think I'm fine heat-wise, however now I'm quite concerned that the 30 degree slope is too shallow for my zone(6). A 48-60 degree slope would be ideal given my suns path throughout the year, but here I am with a 30 degree poised to reflect away a whole bunch of crucial growing light. Is it as big a deal as I'm thinking? You're so, so right about the ease of covering! The logistics involved in double glazing some of those improved structures are INTENSE.. and I would prefer to just glaze the way it is and maybe rebuilt next season if it's a huge problem. (And then again if snowload is a problem? haha) |
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- Posted by Cole_Robbie none (My Page) on Tue, Jan 15, 13 at 12:57
| A 48-60 degree slope would be ideal given my suns path throughout the year, but here I am with a 30 degree poised to reflect away a whole bunch of crucial growing light. Is it as big a deal as I'm thinking? No, I don't think so. Greenhouse poly doesn't really reflect light. Transmission might be a little more optimal when the light hits it at a perfectly perpendicular angle, but the difference is not much. Besides, you're not that far off from the best angle anyway. I have seen designs built by Amish in zone 6 Ohio for early spring growing, and their roof angle is about 35 degrees. |
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- Posted by BiologyBomber none (My Page) on Wed, Jan 16, 13 at 8:39
| Fantastic!! Thanks so much for the advice! |
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