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DIY Greenhouse size

Good day to all the gardeners!

So I bought a 8m x 3m greenhouse plastic film. It was the only size available at the time and I am desperate to get a structure built because of the heavy rains. I want to build it this sort of style:
images (4).jpg
My inital thought was to build a 2x3m with the straight sides at around 1.50. But when adding up all the sides I'll be short by I think a meter of the film. Could anyone help me work out the size of the greenhouse I can make with 8x3m of film? Also how should I go about attaching it to pvc pipes without it ripping in the wind?

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Joined: Sun Feb 14, 2016 5:18 pm
Location: Davis, California

Re: DIY Greenhouse size

I am not sure about the size but since you are using pvc pipe you could use screws, washers and duct tape to attach. Place a small piece of duct take where you are going to screw through to prevent the film from tearing then screw the film to the pvc pipe, using the washer as another barrier preventing additional tearing. I've used this method for attaching film to my hoop house garden and it works really well, just takes time.

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Super Green Thumb
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Location: TN. 50 years of gardening experience.

Re: DIY Greenhouse size

I built my first green house about 1979 or maybe 1980 with 2x4 lumber and covered it with polyethylene plastic. Plastic was stapled to the boards, one day a 30 mph wind blew all the plastic off so I re attached it with lattice boards and nails. Next problem plastic is flexible the wind makes it suck IN/OUT like a bellows the greenhouse was same temperature inside as outside it never warmed up on a windy day and too hot if the wind did not blow. I replaced the flexible plastic with 4'x8' fiberglass skylight panels it was better but still flexible and only lasted a few years. Next I replaced the fiberglass with sliding glass patio door glass my green house turned into a 180 oven. Next problem was trying to keep it from getting 180 degrees inside the green house. 2 fans would not suck out the heat with the door open my green house was about the size of the one shown it your photo. I used a 70 degree snap disc thermostat to turn the fans on. My fans were too small, I lost interest and quit working on it. I had a thermostat inside the greenhouse on a bright sunny winter day with 6" of snow and 20 degrees outside it was 70 degrees in the green house. On a 50 degree day it was 130 in the green house but at night it was below freezing. I experimented with large tanks of water to store heat but I never did get it figured out temperature was too extreme, too hot on a sunny day and below freezing after dark.

I still want a green house for winter tomatoes. The wind here at my geographical location blows in a south east direction almost all the time if I build another green house I need to take advantage of the wind to help fans remove the heat using a thermostat, fans, and louvers. The green house still needs heat after dark.

Farmers coop in town has 3 large green houses and the Amish garden center has a very large green house. When you open their greenhouse door air blows out so it must have positive air pressure to blow bugs away from the door to make it hard for bugs to get in.

I hope this gives you some useful ideas.
Last edited by Gary350 on Thu Feb 25, 2016 12:54 pm, edited 2 times in total.

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Location: hawaii, zone 12a 587 ft elev.

Re: DIY Greenhouse size

I don't know about building greenhouses, but I do know they need vents to provide air circulation and dissipate heat on hot days. low vents and roof vent as hot air rises. The best hothouse we have has an offset roof with window vents. Solar fans are used to cool and move air within the house. It takes two solar panels to operate one fan. If you have one fan at one end and another fan at the other running in reverse, it allows for the best air movement and requires fewer fans. On a small greenhouse it may not matter but on larger greenhouses the fan only goes halfway from one side and where air circulation is poorest is where the insect and disease problem starts.
It also helps to build a double entry as a barrier to bugs getting in but also if it is heated, to keep the heat in too.
https://gardenandgreenhouse.net/index.ph ... entilation
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