Originally Posted by taxlady
GLC, please explain about the hoophouse. It somehow protects the plants from excessive heat?
In the photo, it was rigged with mesh shade cloth last summer. Now, it has white plastic, and the ends will be closed in before winter. A small plastic hot room section inside can be heated on the rare very cold night for things like the citrus.
White plastic cover strikes the best medium. I use 6mil white 55% film. That allows enough light in for plants that don't require absolute full sun and won't take the pounding heat that no amount of watering can save. It has also been shown to be effective in winter. Here, a considerable amount of night heat in cold weather is from the ground, which never freezes. White has somewhat better characteristics under those conditions and also provides some shade.
The peak of the arch is at about nine feet. There will be summer openings in the ends at the top to allow heat to escape, and louver vents either side of the door and a large vent on the other end will provide more air flow. I can wheel in a five-foot diameter fan, if things get too bad, but we have nearly constant breeze.
At 18x40 feet, it's large enough that there's some air cooling effect from the shade. And I can add the black shade cloth back in if needed. I will probably do that at one end where I want to propagate a bunch of cast iron plant that needs deep shade.
This first house is many kinds of experiments in construction and strorm survival, covering material, ventilation, depth of shade, growing media, etc. There will ultimately be at least four of these side by side.
They can be made any size. A smaller house can be made with small diameter PVC pipe. I drove 2-foot pieces of heavy rebar into the ground every four feet and made up 30-foot pieces of pipe. Two people can walk the ends to the rebar and bend it up into place. Another piece of pipe runs the length of the top of the arc and is carriage bolted to each. I have since attached a pipe down each side, five feet off the ground, treated 2x4 along the bottom sides, and another pipe attached to that. Cover is held on with plastic clips that snap over the cover and grip the pipe. The cover can be released from the bottom pipe and rolled up for the summer.
The snap clamps come from:
Snap Clamps - Covering Accessories | Greenhouse Megastore
But I get the film from FarmTek. They also have remnants for small projects, like narrow row covers.
Sun Master® Pull and Cut Greenhouse Film - FarmTek
A ten-foot wide backyard greenhouse could easily be made with with 20-foot pieces of 1-inch PVC pipe, placing them three feet apart for as long as you wanted it.
You can also make classier shapes.
For just a shadehouse and some modest cold protection, the ends wouldn't even have to be closed. Makes a good garden work shelter, too. Keeps out the rain and sun but has plenty of light. I'll make an additional one as a tractor shelter. Good, too, where hail is a problem and destroys plants.
The temperature differentials between different coverings are significant. I'll link a study. In their study, on the warmest day, under clear plastic, temperature reached 38C. Under white, it reached 25C. Under double white, it was 21C. Double layers is a bit much for me, so I use one. On the coldest day, at the coldest time, the difference between white and clear was less then one degree, and both were warmer than outside by about three degrees, so white works about as well in winter as clear. I only need a few degrees of protection in winter (in case we ever have another winter) and mostly protection from pounding sun in summer.