Greenhouse wall materials

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timmmay

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# 141050 28-Feb-2014 08:32

I'm having a greenhouse built at the moment, but we haven't decided on the wall material yet. It's a wooden frame greenhouse made of 4x2 wood, 4.5m x 2.2m, concrete slab floor. It's right beside a bank so external access is difficult, there's a few trees around, and it's fairly windy there so strength may be important. The main reason I'm having it built is the wind kills my plants, summer and winter.

It will be to grow seasonal vegetables. I'm not trying to grow tomatoes or strawberries in winter, so I don't need it super hot in winter, in summer the challenge is cooling it down - lots of windows.

Wall options:
- Glass (fragile so occasional replacement, labor intensive, low to average price, average insulation)
- Single thickness perspex (very strong, not much labor, medium to high price, average insulation)
- Double wall thickness perspex (strong, average labor, medium to high price, good insulation)
- Wavy clear plastic (average strength, average labour, average price, poor insulation)

Ceiling options:
- Perspex (may let in too much heat/light in summer, good in winter)
- Semi-opaque plastic (will help prevent it getting too hot in summer, in winter the sun's low so won't prevent much sun getting in)

Any thoughts?

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# 996001 28-Feb-2014 08:40

I used 8mm twinwall from PSP in Petone, not cheap but really easy to work with plus the other benefits you mention.

timmmay

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# 996015 28-Feb-2014 08:47

Yep the 8mm twinwall is the one I have in mind. It's about the same price as perspex, I guess because of the air gap there's less material. Did you use it for the ceiling too? Wondering if I'd need to add shade cloth or something in summer.

I wonder how much the insulation matters. A greenhouse isn't exactly airtight.

kiwitrc

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# 996030 28-Feb-2014 08:55

Yes used it all over, it gets bloody hot so some ventilation and possibly shade cloth (or 50% cover like trellis) might be a good idea. Not sure if its the insulation qualities but its toasty in there even on a cold winters day with a little sun. PM me if you want to come and have a look.

timmmay

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# 997035 1-Mar-2014 13:57

Hey mate, thanks for showing me your greenhouse. That material looks great, and nice ideas on that fixing between them and the screws. Pretty sure I'll go with it, pretty expensive compared with standard wavy clear plastic but much better insulation and durability.

richms

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# 997039 1-Mar-2014 14:01

Is that anything like core flute (sp?) If so then watch for water buildup in the channels and the resulting mold or whatever that grows inside it.

Richard rich.ms

timmmay

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# 997045 1-Mar-2014 14:06

Yes you do have to be careful of that. You use special tape top and bottom, plus flashings to protect it.

kiwigander

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# 998189 3-Mar-2014 14:19

Has this greenhouse got access to mains power, or can power be run to it without too much strife?

I'd strongly recommend that you put an extractor fan near the top of the leeward gable end. Control it with a riser thermostat.

I had to do this with a greenhouse in Vancouver, Canada, some years ago. Even in that relatively chilly climate the greenhouse overheated until I put the fan in.

If you've got no feasible access to mains power, maybe photovoltaic would be the answer; when you need the fan you should have the power.

kiwitrc

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# 998190 3-Mar-2014 14:21

kiwigander: Has this greenhouse got access to mains power, or can power be run to it without too much strife?

I'd strongly recommend that you put an extractor fan near the top of the leeward gable end. Control it with a riser thermostat.

I had to do this with a greenhouse in Vancouver, Canada, some years ago. Even in that relatively chilly climate the greenhouse overheated until I put the fan in.

If you've got no feasible access to mains power, maybe photovoltaic would be the answer; when you need the fan you should have the power.

Couldnt agree more, it gets thermonuclear in there without ventilation :)

timmmay

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# 998202 3-Mar-2014 14:47

I could put mains power in, but probably won't initially. A solar extractor could work though, the greenhouse will get HEAPS of sun. We have five windows and two doors so should be ok.

mattwnz

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# 998208 3-Mar-2014 15:03

What about polycarbonate. I have an old green house which has horticultural glass in it, and the glass has only broken when kids have hit a ball through it. The glass slid into the frame. Horticultural glass it low grade thin glass. Otherwise glass should be the most durable as it isn't affected by uv light, so should last almost forever.

I use these guys, and it should give you some ideas http://www.redpath.co.nz/domestic-greenhouses-home-products-original/glasshouse-structures-aluminium-frames-glass-cladding/glasshouse-models.html

I have also been helping someone put up a commercial greenhouse, which is a is twin walled plastic one. THe downside is that it needs a pump to keep it inflated, and over time the plastic walls will need replacing.

kiwitrc

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# 998246 3-Mar-2014 16:03

The twinwall mentioned above is polycarbonate.

lapimate

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# 998312 3-Mar-2014 18:04

timmmay:... we haven't decided on the wall material yet ...

Is not UV transparency a parameter to consider in relation to plant growth? Have you been able to compare values for glass and the various plastics?

timmmay

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# 998394 3-Mar-2014 20:32

Isn't perspex and polycarbonate much the same thing?

If anyone knows about which is best for plants let me know, but I think they'll all work ok according to the greenhouse book I have. UV helps plants grow, so I wouldn't want anything that blocks too much out.

richms

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# 998397 3-Mar-2014 20:33

Perspex is a brand of acrylic. It is more brittle and chip prone when cutting but the edges will flame polish up nicer than polycarbonate

Richard rich.ms

timmmay

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# 998401 3-Mar-2014 20:34

I'm not going to polish anything. If it's lucky I'll hose it down occasionally :)

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