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Any input on our solar greenhouse design/layout before I start with architectural drawings?  RSS feed

 
Ian Taylor
Posts: 59
Location: Grafton NY, 25 Miles east of Albany
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I am planning on putting a solar greenhouse in on our property over this next coming year and just to get my ideas down I made up some scale drawings on the computer. It is going to be attached to our house by an enclosed breezeway and is going to be replacing a garage that is there currently which luckily already faces perfectly south:



The garage that is there is 15x20 and the greenhouse is going to be 15x30 with the extra 10ft extended forward toward the camera, at the same time I plan to enclose the breezeway seen in the picture as well. We are located in Upstate NY on a plateau about 20 miles from Albany, I figure it would be great to have for winter gardening seeing as I only work 1-2 days a week in the winter and our growing seasons tends to be on the short side here. I'm planning to sink the floor 2 feet below ground to act as thermal mass and i'm going to make the foundation out of concrete block and just leave the floor open to drain right into the ground.


Here is a side view:



Here is a top down view:



The blue is the 1000gal aquaponics setup I would like to buy around the same time and the associated grow beds. I would like to be able to grow tropical plants like dwarf avocado, lemon and banana trees with the unapportioned space in the picture. I dont think we should have an issue with heating, I have a large woodstove and a nearly unlimited supply of free wood since we live on 90 mostly wooded acres and there is so much thermal mass in the structure and right around the woodstove that even if I don't have a fire for a few days at a stretch it shouldn't get too cold. Between the tropical plants and i'd like to keep tilapia in the water it will have to stay fairly warm. I am also going to run 2 insulated 4" ducts through the breezeway and constantly exchange air with the house to provide co2 for the plants and to heat either the house or greenhouse with the excess heat in the winter. I am also going to have a couple of automatic vents in case it gets too hot, I would like for it to be similar to a tropical climate in there year round.

The wood is going to be harvested on site, we have a couple of large douglas fir that are going to be shading the greenhouse so i'm going to cut them down and mill them. I have read that this is a fairly rot resistant wood, does anyone have experience with using this in a greenhouse? The only other abundant options are red and white pine and neither of those are at all rot resistant or black locust which is terribly hard to mill and work with and i'd rather use it for fence posts. I can also salvage plywood and paneling from the garage and I might reuse a couple other odds and ends like the windows and siding. The garage is made from white pine so I think ill use the structural lumber from that just for finishing the breezeway.

I have budgeted about $5000 for the project in total which I think is a pretty fair estimate. The wood will be nearly free and I have a JD350 bulldozer/loader to excavate it myself and for ripping up the slab the garage rests on. I priced the all the block out at 580+delivery and then ill need to buy mortar, crushed stone, a little bit of concrete for a footing (But I have a 1/3 cubic yard mixer), insulation, bracketry and the glazing which will be 6mm double wall poly, so that leaves about 4250 for all that stuff. Hopefully it doesn't cost much more because i'd like to buy all our aquaponic stuff at the same time and the tank I am looking at is too big to get in there without taking a wall off, ill have to buy that before I frame it.

Does anyone have any suggestions on stuff that could be improved?
 
Adam Klaus
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Location: 6200' westen slope of colorado, zone 6
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My experience with cold climate solar greenhouses is that tropical plants are not worth the effort. They will never thrive, their productivity will be minimal, and they really are there mostly for the foliage and the novelty factor. I would recommend considering more mediterranean plants, things that would not grow in your climate outside, and that tolerate hotter summers than the tropical plants will. This will be much better matched to the actual conditions in your solar greenhouse, where even with your best efforts, there will be considerable seasonal fluctuation. The tropics just dont have the cooler winters and hotter summers that you will have. So plants like figs, persimmons, olives, passionfruit are form a much better target ecology.

I would invest in triple wall polycarbonate, if not the new quad wall stuff. Double wall is going to lose way too much heat in winter.

Dont underestimate the massive amount of ventilation you will need in summer to exhaust the buildup of hot air. Your design is good for harvesting solar energy, and will quickly become a solar oven in summer without a huge amount of air exchange. Think intakes down low and much larger exhausts up high.

Check out the 'solar battery' concept. It was pioneered at CRMPI (Colorado Rocky Mountain Permaculture Institute), and it is the single best tool for evening out the temperature extremes that are a fact of life in a temperate solar greenhouse. I cant emphasize enough how much this feature will increase your performance in both summer and winter, from the examples I have seen.

The climate battery generates much more gentle heat than a woodstove. In the same way that the radiant heat from the woodstove really warms your skin, it similarly really cooks plant foliage, IME. I used to have a woodstove in my greenhouse, and found that it did more harm than good. It shocked the plants, and harmed them more than a little bit of cool air. Plants arent too fond of fire.

4" ducting wont move enough air to matter. You dont need to replace CO2 in the greenhouse, that wont be a problem. If you want to move greenhouse air into your house, use 6" minimum ducting. You would create some vulnerabilities having that ducting, in terms of cold air infiltration. Given the cost of ducting and fans, I would skip this. Utilitze the ducting and fans in a climate battery and you will get much more bang for the buck.

Sinking the greenhouse into the ground, and leaving the natural grade as your floor are excellent ideas.

My guess is that your budget is too low. Once your project gets going, it is all the small stuff that will be your budget-busters. Skip the aquaponics for now and focus on a top quality greenhouse. Much better than spreading your finances too thin, and compromising the permanent aspects of your building.

good luck! feel free to ask more questions as they come up. much better to over plan than to under prepare.
 
Ian Taylor
Posts: 59
Location: Grafton NY, 25 Miles east of Albany
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Yeah I figured there would be an issue with the wood stove putting out too much radiant heat which is why I was going to put it in a concrete vestibule and not near any of the plants. Ill look into how much it would cost for the piping to make a climate battery, it would be easy since I already have to dig down below the floor as is. And yeah all the similar structures I have seen have tons of ventilation for excess summertime heat, I didn't include it in the drawing but I was going to have some large vents at the top and bottom to make a chimney effect and keep the heat flowing out.

And i'm not too dead set on tropical plants besides avocado, that's the only one I have decided I am going to bend over backwards to make grow since I like them so much hahah, they aren't necessarily tropical plants though, they grow all through southern CA. Ill see what other options I have, are there dwarf olives that produce reasonably well in a setting like that?
 
Johnny Niamert
Posts: 268
Location: Colo
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Here was my rough idea for a greenhouse. This sketch still has black water barrels, in a 'passive' design. Glazing would only be on the left (south) side. The angles of glazing are set-up for 40' N.



I was thinking of incorporating, in the upper corners, one of the glazing rectangles into a solar water heat exchange, and another rectangle into a photo-voltaic cell for energy. I would daisy-chain all the barrels. I figure this way the water would get better mixed and heated, and I'd have enough energy to run a small pump, which could better heat the water in a solar water exchange set-up during winter. Maybe even a diverted set-up to bypass the solar exchange for nighttime into a radiator/fan set-up to warm and move air.

After talking and meeting with Adam, I was very intrigued by the climate battery idea. It would be more initial work and cost, but I could imagine the benefits. I may possibly try a hybrid of both climate battery and barrels, run off solar. I'm mainly planning on year-round growing my diet staples, though, not plants that are widely out of my zone.
 
Adam Klaus
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Posts: 946
Location: 6200' westen slope of colorado, zone 6
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Ian Taylor wrote:
And i'm not too dead set on tropical plants besides avocado, that's the only one I have decided I am going to bend over backwards to make grow since I like them so much hahah, they aren't necessarily tropical plants though, they grow all through southern CA. Ill see what other options I have, are there dwarf olives that produce reasonably well in a setting like that?


I have never seen avocados produce outside their natural growing climate, despite many many efforts. Jerome at CRMPI gets bananas and papayas, but no avocados (so far). They are not an easy or adaptable tree species. They are shallow rooted, non-dwarfing, and require two for pollination. Even in California they grow in a very narrow range.

Olives can be pruned to any size, are self-fertile, and are highly adaptable. They handle freezing temps into the teens, and heat well past one hundred. So yes, they are a good choice for a greenhouse. I have one in my greenhouse, an Arbequina, that is growing well. No fruit yet, but it seems like fruit is getting close.
 
Adam Klaus
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Posts: 946
Location: 6200' westen slope of colorado, zone 6
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Johnny Niamert wrote: I'm mainly planning on year-round growing my diet staples, though, not plants that are widely out of my zone.


This is some very good thinking Johnny!
 
Tim Malacarne
Posts: 226
Location: South central Illinois, USA
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Rodale Press has some excellent books on this subject, I'd try to read them... The Solar Greenhouse Book is one.... They'd advise perimeter rigid insulation outside the walls, I think. Seems to me I've read of hoop houses in your state that used row covers in addition to the tunnels and the cool weather crops did fine over the winter. I don't think tropicals will work for you. Also there's a formula for designing the optimum angle for the south facing glazing. If it were me, and I was on 90 acres, I'd see if I could attach the GH to the garage, keep the garage too... So, does the large garage door face south?
 
Ian Taylor
Posts: 59
Location: Grafton NY, 25 Miles east of Albany
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The little window that you see faces south, The garage door is to the east. And I have no interest in keeping the garage, in the year we have lived here the only thing I have used it for is storing firewood, its too small to park anything in and we have an actual one car garage in our walk out basement. I was going to build another one about twice as big across the yard, possibly with some of the scraps from this one. And I ordered the book you are talking about but haven't got it in the mail yet. What do you mean by rigid insulation? I was going to build it as a stick frame insulated wall like in a house and just stain the plywood on the inside so its less likely to rot. The R value from a well insulated conventional wall is still pretty high. And yeah I saw the method for calculating the glazing angle although if I followed it the greenhouse would be about 100 feet tall unless I squared the top off.

And what I think would really be a great idea would be abutting it up against the house but i'm not sure if we are going to keep this house forever and I dont want them sharing a wall if we end up doing anything with the house, too much of a pain to demolish. What we may do if we build something new at some point is place it right up against the greenhouse, now they are about 6 feet away and connected by a 6ft wide breezeway which will be enclosed and insulated.
 
Tim Malacarne
Posts: 226
Location: South central Illinois, USA
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By rigid insulation, I was meaning styrofoamy kinda stuff to use against the foundation, your heat sink I was supposing. A solid masonry wall will conduct massive amounts of heat...

I don't think you'll be sorry you ordered the Rodale book. It ought to help. And yes, I laughed at the 100' tall thing! I've thought if I ever alter the roofline to sorta square off the very top, and put the ventilators in that section.

FWIW, looks to me like an ideal setup for a south-facing greenhouse or solar growhole. Best of luck to you, please keep us up to date!
 
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