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Greenhouse too hot

We have moved into a house in Cumbria which the previous owners left a small greenhouse. Unfortunately, the only ventilation is via the door. We have some tomatoes in which up until yesterday were coping quite well until the evening when I noticed severe limping (from the toms not me, although .....). Anyway, we intend to get a 'real' greenhouse later on which will have the usual ventilation, i.e. auto roof opening etc. To cut a long story short so I don't bore you all to death, is there a way I can get around this problem? Was thinking about a solar panel generated fan if one is available.
Any help or advice would be appreciated.




  • ButtercupdaysButtercupdays Posts: 4,462
    Shade the roof :) The simplest and easiest way is to use a spray-on shade whitener - I have used one called Snowpaque or something similar in the past. You just mix it with water and use a spray bottle to apply. Once dried it doesn't wash off in the rain (if you get any!) but you can use a soft brush to remove it later in the season.
  • JennyJJennyJ Posts: 9,626
    Or throw some shading fabric or fine netting or old net curtains or similar over the roof as a quick, easily removable fix for sunny days, as long as it's not windy. The "correct" way I believe is to fasten shading fabric to the inside of the greenhouse but that might be tricky when it's full of tomatoes.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • PlantmindedPlantminded Posts: 2,790
    My father used to put a piece of washing line inside the greenhouse below the apex of the roof and drape a cotton sheet like a tent over it, attaching the four corners of the sheet to the inside corners of the greenhouse.  The tomatoes seemed to like it!
    Wirral. Sandy, free draining soil.

  • MeddyliolMeddyliol Posts: 12
    Thanks a lot. Excellent ideas. The spray stuff or washing line seems to be a good idea but not discounting the others of course.

  • NollieNollie Posts: 7,329
    As well as shade netting, if you plan to replace it anyway, could you remove some panes from the end opposite the door to get some through breeze and prevent the build up of both heat and humidity? Tomatoes prefer it drier, they really don’t like high humidity.
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • hulmephilhulmephil Posts: 3
    I fixed a sheet of opaque, white polythene (polytunnel cover) on the inside face of my greenhouse roof; it has worked quite well and doesn't block out much light. I've also used a paint on liquid called Cool glass, which is fairly effective.
  • PosyPosy Posts: 3,601
    I found that I got really fed up trying to take netting down when it was cloudy and putting it back up when the sun came out. Now I use Nixol. It's a powder you mix with water and paint or spray on the outside of the glass. When it rains, it becomes virtually clear but in sunshine it is opaque. You can make it lighter or denser and it lasts all summer.
    It doesn't look particularly attractive because it is difficult to get an even finish but it really works wonders.
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