Polycarbonate versus glass greenhouses

Do-it-yourself projects such as greenhouse or shadehouse builds and related topics.

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Polycarbonate versus glass greenhouses

Post by Rizzo170 » Thu Apr 14, 2011 8:30 pm

Hello Everyone

I need to replace my aging little polytunnel with a greenhouse (about 12 ft x 8 ft) and am wondering whether to get glass or twin wall polycarbonate. I would prefer polycarbonate for safety reasons but as I live in Britain and we don't get too much sun at times, I don't know whether it would let enough light through for the cacti to flower or whether glass would be better.

Hoping someone can give me some advice.


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Post by apfire » Fri Apr 15, 2011 3:31 am

My little greenhouse is made with triple layer Poly. According to the manufacture it lets in 70 percent of the the sunlight. It also offers better insulation. I am new to cacti, but I have been raising lowland Nepenthes in my greenhouse with no problems. But I live in Florida and get plenty of sunlight.
I am just looking for the defining statement to put here. Follow this link to see my other cacti.
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Post by daiv » Fri Apr 15, 2011 9:44 pm

Hi Rizzo,
The manufacturers should have information about the light transmission with both the poly and the glass so you could compare. Glass can vary quite a bit in the amount and type of light that it lets in so even though it looks so clear, sometimes it is surprising how much light is being blocked by glass.

Even though you are in England, you should be getting lots of light in the summer time and you won't need to worry quite as much about light levels in the cooler winter with plants inside or dormant.

Your challenge will be spring/fall when greenhouse temps can be high in relation to light levels. I think you can help combat etiolation and such by just waiting for the first water and cutting it off in the fall for the winter.

All Cacti are succulents, but not all succulents are Cacti

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Post by hob » Fri Apr 15, 2011 10:20 pm

both of mine are glass but having said that i have seen a lot of glass ones with some shading, i do some shading myself.
just as important to consider is ventilation, with a 12 ft x 8 ft i would be looking at putting at least 2 if not 3 automatic opening roof vents and also a side or end louvre as well.
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Post by Buck Hemenway » Sat Apr 16, 2011 10:51 pm

Hi Rizzo, They make that stuff in varying degrees of sun block, from none up to 80% or so. You will need to do am little shopping, but should find what you want.
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Post by Rizzo170 » Sat Jun 18, 2011 6:02 pm

Hi everyone

Thank you to all who sent messages about what sort of greenhouse to buy. We have finally got one. Our son is in the middle of putting it up. We had to get a polycarbonate one in the end anyway because of the cost of glass ones. I can't wait to get the plants moved in and see the coming flowers.

Happy growing

Rizzo :)

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Post by ali » Sat Jun 18, 2011 6:31 pm

Congratulations Rizzo!
I hope the best growing for your plants.

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