greenhouse design.

[bil]

OK, if I can raise the money, I can build myself a greenhouse to house orchids during the lousy weather in winter.

I have a footprint of about 4 metres long and 2.5 wide, with a door in the middle of a long side.

So, bearing in mind that it will be to house orchids, what design features should I include?

Ventilation, shading... it will be housing Dendrobiums, soft and hard cane, a couple of vandas, Catts and some cymbs. Poss Phals too.

The winters can be very rainy at times, with very heavy rain, and sometimes high winds. Temp at worst down to minus 7C altho almost always if you are a late riser you would never know there had been a frost.

Frosty time just Jan and Feb.

Suggestions and advice please especially comments along the lines of "I wish I had..."

[sbrofio]

Well, Dens, Catts, Vanda and phals have different minimum temps request during winter. My big hybrid Cymbidium stay outside at -7°C under the snow without problems. Vanda (except some species es coerulescens), can stay to 10-12° but 16° would be better, and the same for Phals.
With these things in mind, I'll divide the greenhouse in 2 parts with a panel (polycarbonate alveolar panel), one heated (Vanda, Phals Catts and some Dens), and the other not heated directly but, being just divided with a panel, colder than the hotter but hotter than outside.
If I had money, I'll build a double panel greenhouse (polycarbonate alveolar panel - 2/3 cm empty - another panel).
I surely will put a fan (or 2) to avoid rot.

[sbrofio]

a quick pic to explain better:
up left: the external wall of the greenhouse.
Out - P (panel) - E (empty) - P (panel).

down, the middle panel (darker) to separate different temps rooms.

and here the material I'd use: (much rooms inside the panel-> much thermal isolation you have)
https://www.google.it/search?q=panne...w=1920&bih=965

[bil]

Originally Posted by sbrofio

Well, Dens, Catts, Vanda and phals have different minimum temps request during winter. My big hybrid Cymbidium stay outside at -7°C under the snow without problems. Vanda (except some species es coerulescens), can stay to 10-12° but 16° would be better, and the same for Phals.
With these things in mind, I'll divide the greenhouse in 2 parts with a panel (polycarbonate alveolar panel), one heated (Vanda, Phals Catts and some Dens), and the other not heated directly but, being just divided with a panel, colder than the hotter but hotter than outside.
If I had money, I'll build a double panel greenhouse (polycarbonate alveolar panel - 2/3 cm empty - another panel).
I surely will put a fan (or 2) to avoid rot.

Hmmm, as you say, a double wall with two twinwall sheets would be fabulous, but that would double the cost. I simply haven't got that kind of money. Plus of course the panels have to be framed to hold them together, and the has to be steel, as termites would eat a wood frame very quickly.

[sbrofio]

you could bo in wood but well treathned with special products like yatch wood to avoid rot fo the wood and to avoid termites to attack. Also, to spend less money, you can use rigid panels outside, structure in the middle and bubblw wrap sheets inside. They isolate very well and the cost is much less, Much better you isolate, less you will spend to keep it warm.

[bil]

Originally Posted by sbrofio

you could bo in wood but well treathned with special products like yatch wood to avoid rot fo the wood and to avoid termites to attack. Also, to spend less money, you can use rigid panels outside, structure in the middle and bubblw wrap sheets inside. They isolate very well and the cost is much less, Much better you isolate, less you will spend to keep it warm.

Very true. Sadly I don't have a lot of choice here with wood treatments, and the only one I could find was eye wateringly expensive. With the termite problem everyone just builds in stone, brick etc. In addition, the radical shifts in temp and humidity make wood constructions very prone to warping. I learned to weld precisely because of those problems.