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Post by oldmobie on Sept 16, 2016 21:48:09 GMT -5
My wife has authorized me to design a greenhouse and have it built. (There's currently no budget for it, but that's a minor detail.) Trouble is I don't know exactly how I want it to be. Huge, warm, free, fun and self-assembling would be awesome, but so far I haven't found one like that. I do know that I don't plan to use it commercially, or to pay to heat it. If I can work out a free fuel to burn and enough thermal mass to stabilize the temp, rather than have the highs and lows all over the place, I may heat it. Otherwise it should be a season extending cold frame, similar in purpose to what Joseph Lofthouse uses. I'm thinking it might be fun to see how cheaply I can put it together. Having it be a piece of junk and fall apart would be less fun. So I'm trying to cobble together a plan that falls between those two extremes. I'll show below what it looks like (in my head) so far:  This 10'X20' carport is about $150 at Harbor Freight. $100 if I catch it on sale. The 2'X8' polycarbonate panels below run about $20 each at Lowe's. I think I'd need them to replace the carport's original roof, as well as cover the walls.  I have a bunch of vinyl windows that were replaced during the remodel. I'd try to use them to provide a bunch of ventilation. I may need to design in a peak or gable vent as well. I'd like to keep the whole thing still by driving a T post next to each of the legs of the carport and wiring (or better still bolting) them. Seems to me that my design is lacking horizontal "nailers" and could probably use studs as well. If the price is right, I'd like to use a material more permanent than lumber. I don't know where to source or price a solution in metal. For thermal mass, I have a metal stock tank (70 gallons, I think) and an IBC tote. I'd fill both with water and paint them black if needed. So what do you think? Can this idea be made useful and durable for less than the cost of a similarly sized kit? |
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Post by steev on Sept 16, 2016 22:39:55 GMT -5
The polycarbonate stuff is pretty good for roof/siding; the stock-tank is good thermal mass, though small, on the inside south side, with shelves/tables built over; paint its south side black; might want more than one; 160's are pretty good. Having no clue of your weather situation, I can't comment on strength of structure; personally, I tend to go for "out-last me", but I'm not gonna sell and I'd rather not re-build, as I'll be too damn old when it would be needed.
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Post by prairiegarden on Sept 17, 2016 10:17:28 GMT -5
I don't know where you are but if you have access to sucker rod that they use for drilling it's really strong. I picked up some 1 inch by 22 foot sucker rod for $10 a rod, the main problem so far has been getting the stuff into an arch shape as it is VERY stiff and strong..I also have some 3/4 inch stuff and it would probably have been strong enough. What I want to do is weld a 3/4 inch rod across the bottom to hold the shape in place, it will give a 14 foot wide by about 8 foot high arch with fairly straight sides. I wouldn't trust just a wooden frame to hold it in place, we pulled the ends together with a 3 pulley chain hoist and tied it with brand new rope, when we slackened the pulley, the 3/4 inch poly rope stretched almost 2 feet, we had to double it up for it to hold the distance.
Once the arches are made you can connect one to the other with wood slats or fasten/weld another rod across the top or sides. The arch shape is very strong and also handles wind well. just a thought, as around here those carport adaptations tend to fail without attention whenever it snows, I was looking at them for a while. If it doesn't snow then the question probably isn't pertinent. I wondered if you could fill the legs with some sort of cement to add strength but never found anything that seemed as though it would be useful.
Some people have used rebar which will work but it is weaker than sucker rod and in my area, more expensive. It needs more reinforcing if heavy snow loads are a possibility, some people who have skimped a bit have had failure, but others in areas of heavy snowloads have used them for years. Probably either rebar or sucker rod should be painted or wrapped to stop both rust and the degradation of the plastic from the dark steel getting hot and or rubbing against the plastic. That said, it's been used successfully in Manitoba as well as other place. The rods are so slender that they throw very little shadow, probably 4-5 of them the same shadow as one 2x4.
One thing that seems consistent with all the research I've done, is that a double layer of covering should be the first line of defense in trying to maintain heat in the thing.
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Post by philagardener on Sept 17, 2016 13:07:26 GMT -5
Nifty, oldmobie ! If you are going the polycarbonate panel route, check out the HF greenhouses. Joseph seems happy with his and there are lots of instructions on the web about strengthening the structure and anchoring the panels. After you cost it out, it might not wind up being that much more expensive. Any way you go, be sure to take lots of pictures! |
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Post by walt on Sept 17, 2016 13:08:19 GMT -5
About 20 years ago I built a greenhouse by digging a 20' x 20' hole in the south facing side of a valley. I lined it with free used railroad ties, roofed it with 4' x 8' glass from a huge solar collector that was being taken down, also free. The door was an old storm door, free. The 2x6 rafters weren't free.
The floor was dug in a stairstep fashion, and the roof stuck about a foot above the outside ground. The floor was deep enough I could stand straight in it, about 6'.
It had no insulation or heater. Tomato plants survived a couple of winters in it. They didn't actually grow or ripen fruit between late November until March. But the green tomatoes formed by November went ahead and finished ripening in march or April.
After a few years a huge (for central Kansas) blizzard piled 3' of snow on it and the roof collapsed.
Where I live now, I built a 10 ft x20ft greenhouse on the south side of my house. I used 2x4 rafters and polycarbonate sheets from Low's. There were patio doors on the south side of the house, and I heat the greenhouse by opening the patio doors and let house heat into the greenhouse.
With the greenhouse's second winter coming, I'm installing 4'x8' styrofoam panels on hinges so they can be swung up at night to turn the whole greenhouse into a giant styrofoam picnic basket at night, even on days that are cloudy and nasty cold. Days the panels can be down against the house wall. Nights the panels will be up against the greenhouse roof.
Thermal mass is the floor and the side of the house, and 5 barrels of water.
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Post by prairiegarden on Nov 4, 2016 8:55:32 GMT -5
My straw bales never got here again this fall, heavy rain and then three weeks of intermittent rain is not good for bales. So when an 11x20 portable carport sans cover showed up last week for $50 I snaffled it, got it put back together yesterday. It has 6 ribs and I still wouldn't trust it to handle much in the way of snow load, the pipe is very thin walled.
Today the plan is putting clothesline cable reinforcing running from mid end rib to base of second rib front and back to try to give it a bit more rigidity, and 3inch x 7 foot posts in each corner ( cause I have them) to help stop it from blowing over or away..now I think of it with the posts I probable don't need the cable. So might use it instead to cross from side to side at roof line..about 6 feet high which is plenty high for me and might help it cope with snow a bit better.
It will just be getting builders 6 mil plastic this winter, to get the lovely rigid greenhouse panels would be about $200 each to bring them so that's not going to happen, and we are normally deep into winter now so can't count on the weather to stay nice for 2 weeks until the real greenhouse plastic arrives. So next spring, if this plastic is still in decent shape, will probably just make a second skin for it. Then if/when I ever get bales they will be put one high on the front (south) then stacked two or even three high on sides and back. The bales are 3 feet x 3 feet x 8 feet long so even outside the thing will help create a microclimate. The idea of the row of bales on the south is to slow down frost penetration.
Vents at the top on both ends with the plastic on the south wall arranged so it can be rolled up if needed. Hoping this will work and Im not missing anything!
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Post by prairiegarden on Nov 6, 2016 18:25:45 GMT -5
Well. Delighted with the posts pounded into the inside corners of the greenhouse, it's now totally rigid with no way to sway and certainly no danger of blowing away.
The plastic is another story and I'm thinking I need to find some sort of panelling that will work. It keep wanting to sag between the ribs, we can't seem to be able to get it very tight. With the winds we often get here I've little faith it will stand up to them unless it's almost drum tight and we can't get it anywhere near that. So time to call all the restore places and check all the kijiji ads and hope for the best, even if just the roof it would help.
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Post by jondear on Nov 6, 2016 18:56:14 GMT -5
Maybe a double layer of poly with a blower?
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Post by oldmobie on Nov 6, 2016 22:30:20 GMT -5
Well. Delighted with the posts pounded into the inside corners of the greenhouse, it's now totally rigid with no way to sway and certainly no danger of blowing away. The plastic is another story and I'm thinking I need to find some sort of panelling that will work. It keep wanting to sag between the ribs, we can't seem to be able to get it very tight. With the winds we often get here I've little faith it will stand up to them unless it's almost drum tight and we can't get it anywhere near that. So time to call all the restore places and check all the kijiji ads and hope for the best, even if just the roof it would help. Glad to know my hunch was right and that the posts stiffen it up and keep it in place. How many ribs did you say it had? How far apart are they? I assume the panels would last longer, but if you're otherwise happy with plastic sheeting, have you considered putting something running across the ribs? (Like where the "nailers" would go for a tin roof?) It'd stiffen the structure a little more, and make for a shorter unsupported span of plastic. I'd considered PVC pipe. I think it'd be nice and smooth for the plastic. It'd work with the panels, too, but would take more effort in that scenario than lumber. |
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Post by prairiegarden on Nov 7, 2016 19:00:22 GMT -5
It's got 6 ribs so 4 feet apart. It also has pipe connecting the ribs at ground level so that helps with stability as well, and the end posts have little extensions so they extend about 8 inches into the doorway. I'm not sure we got all the bits as it looks as though there was or should be pipe extending across from side to side on the ends at ground level as well but we ended up with only one extra piece of pipe and no extra bolts/nuts.  The frame is working just fine as it is though, no complaints. Even before the posts it seemed pretty stable side to side but would sway if encouraged from front to back. Now it's rock solid, fastened the posts to the end ribs so nothing is going anywhere. I think there is a way to get this stuff tight, we just haven't got it sorted yet. Wondering if even the clothesline cable would work, it wouldn't make a significant bulge to stop snow from sliding off. The real greenhouse plastic probly better. The panels would be the way to go though, I think, if only they weren't so expensive! |
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Post by steev on Nov 7, 2016 20:38:34 GMT -5
I hope you're factoring in not just initial expense, but cost of time/labor for shorter-lived parts to be replaced; heirloom quality is spendy, but it's an investment, rather than an expense.
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Post by prairiegarden on Nov 10, 2016 9:53:52 GMT -5
The cost of labour is a highly significant one, if I could do this myself I could have afforded the panels. Not being in town adds to the problems of even finding anyone willing to come out, the local unemployed are not only expensive but useless and surly, at least the guy helping this year is cheerful and willing. Now if only he had some interest and a little more speed and stamina, and was less easilly distracted...I have a fairly limited time I can stand and walk before I have to stop and sit because of arthritis; he tends to think he should stop too, which is not the idea. It's fairly frustrating because even with the help it's taking 5 times as long to get half of the stuff done I could've done myself even 6 years ago. Whine whine whine, At least this guy is cheerful and pleasant to be around, so small blessings are appreciated.
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The frame is working just fine as it is though, no complaints.