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jimigunne98

Greenhouse temperature control: big problem

jimigunne98
11 years ago

I am in S. Texas, zone 9A. I built a greenhouse , about 7 ft. wide and 20 ft. long, out of arched cattle panels, covered with clear film, abt 5 mil. It has been very disappointing. In the summer I have to cover the greenhouse with an opaque tarp that covers all but the bottom foot on each side (but not the ends), and run a high-speed fan sucking air in through the end-window and out the open door at the other end. Yet it still gets very hot. It is so efficient at trapping solar energy that it easily gets up to 115 deg. (when actual air temp is abt. 100 deg.) even with the tarp, if there is not a very high air current flowing through it.
This of course cuts way down on the light available for the plants. In the summer, I think it is still too hot in the afternoon on sunny days for most plants even with the high-speed fan and the shade tarp.
In the winter, when the shade tarp is removed, it gets borderline too hot in the afternoon. So on some warmer winter days the tarp has to go back on . And on very cold nights, even with the tarp left on, the plants might as well be outside without heaters.....so I have to run a 1500 W heater or two with the greenhouse all closed up to prevent a freeze. All in all, this makes the greenhouse of limited use, and uses lots of electricity, not to mention constant vigilance to keep the temp within a good range for the plants. Is there some better design, some solution? Is it maybe the small size of the greenhouse that is making it hard to keep temps at acceptable level?

Comments (5)

  • MichiganFarmer
    11 years ago

    Sounds like you have an issue common to many greenhouse owners. I am still trying to picture exactly the layout of your greenhouse, but I do know that many folks create their greenhouse with the ability to roll up the plastic during the hot temps and then roll it back down at night. If you can run a pvc pipe along side the greenhouse, clamp the plastic sheet to it and roll it up half way during the day, it might do the trick. Best of luck to you! Mike's Plans.

  • fruitnut Z7 4500ft SW TX
    11 years ago

    South Texas is very hot country for a greenhouse. To make it useable you will need an evaporative cooling system and shade cloth like 40-50% aluminet.

    I guess my question is what are you growing that needs a greenhouse? I can see a structure to avoid freezes in winter. But what needs covering in summer?

    I'm growing all kinds of fruit in a greenhouse in west TX at 4500ft elevation. So we're much cooler and lower humidity. This makes a useable greenhouse but only with evaporative cooling, wet wall opposite exhaust fans, and shade cloth. In your climate the best greenhouse will still be 100F in summer and freezing in winter. Mine 32ftx54ftx16ft and covered with inflated double poly still falls to outside temperature at night unless heated.

    Mine benefits from covering in summer because our rainy season would rot the stone fruits. It also excludes hail, wind, birds, etc.

  • barrie2m_(6a, central PA)
    11 years ago

    I'd agree with fruitnut in that you may not need the covering in place most of the time and a film cover that can be pulled to the peak during the day might be a better option. That method is commonly used in the Haygrove high tunnel, popular in Britain. Your main problem in using such a system with cattle panels is that frequent sliding of film over the rusted wire can snag the film and create holes that soon render the whole method useless. I've never had that need in our region and know of many growers in our area that are less than content with the daily workload imposed by Haygrove tunnels but you may want to look into them.

  • foolishpleasure
    11 years ago

    I have a small greenhouse I use it only for winter. In summer I pull out the insulation and plastic film sides. My frame is wood so it is easier to pull the staples out. Although itisstillmpain in the A. I would not imagine putting plants in a greenhouse in summer it will be cooked.

  • jimigunne98
    Original Author
    11 years ago

    Yea, I just need to forget about using the greenhouse at all in hot weather! Thanks all, JIm

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