choosing my first greenhouse, help!

[Lia23]

Hi everyone!
I've decided to buy my first greenhouse and still cannot decide on material. Just a brief description of my situation so you can easily understand my needs. I will be growing intermediate and warm temperature orchids in there and I live in the UK (the temperatures didn't drop below -5 for the last 3 years). The size of the greenhouse I can put in my small garden is 2x2 meters (I guess it's approx. 6x6ft). There is a concrete base in the garden, so I do not know what base I should get for the greenhouse or I do not even need one?
Also, materials!!! is my main concern
I am deciding between toughened glass and polycarbonate sheets. First of all it looks like polycarbonate hold more heat than glass which is good and also it protects from sunburns (harmful UV).
However, toughened glass looks much more attractive (well on pictures, haven't seen in real life). What would you choose?
I've attached two types of them so you can look and have an idea. First one is polycarbonate that is 4mm thick Lacewing™ 6ft x 6ft Deluxe Black Aluminium Frame Greenhouse £222.99
Second one is toughened glass which is 3mm thick
Lacewing™ 6ft x 6ft Deluxe Aluminium Frame Greenhouse with Toughened Glass £271.99

OR this one 3000s polycarbonate with a twin wall at the top... BillyOh 3000S Easy Fit Aluminium Silver Greenhouse with Base and Opening Vent - Greenhouses - Garden Buildings Direct

Please give me your opinions on those 3.

[Ray]

Multi-wall polycarbonate is a much better choice, because, as you noted it is far more insulating, and will be stronger than any tempered glass when in contact with falling or wind-blown objects.

With the types of orchids you intend to grow in it, you will need a heater to keep the temperature in the structure above 10° C or so, so the better insulating the structure, the less you'll spend.

Do not be concerned about UV hitting your plants; nothing protects them in nature, does it? The UV protection in polycarbonate is to protect the polymer. However in good weather, you are going to need to be concerned about heat buildup in the greenhouse, so should be thinking about ventilation and shade.

As far as the base is concerned, a concrete slab would be the easiest to keep clean, but keep in mind that you will be watering in there, so the excess needs to drain.

[estación seca]

I haven't seen a new freestanding glass greenhouse in decades. They're all polycarbonate. There are multiple good reasons for that.

[RosieC]

I agree with the comments above.

Polycarbonate works well. I have a 6'x6' one and I've had a couple of times when a roof panel would have smashed with something heavy falling from above, the panel has moved inwards and needed putting back in place but was unbroken.

To keep it warm in winter you will need a heater. I also line mine with large bubble wrap on the inside. It is sold in garden centres for just this sort of use, I bought some many years ago and take it down each summer and put it up each autumn and it lives in the loft when not in use (it's a great opportunity to clean out the greenhouse while all the plants are out to put up/take down the bubble wrap, however I don't keep all my orchids out there all winter and some from outside move into the greenhouse for the winter so I also use that as the opportunity to move everything around). The bubble wrap has lasted me many years now.

Hubby and I put down a patio with cheep concrete paving slabs and then screwed the greenhouse frame onto that. It's worked great, only thing to bear in mind is ideally it should have a fractional gradient to allow water to drain off, and you need to compensate for that to ensure that your greenhouse frame is level. We have a slight gap under one edge of the greenhouse which is where the water runs out and there are washers where it's screwed to the ground to hold it at the right level.

Make sure you have at least one auto-opening window. I didn't to begin with and £20 or so on an auto-opener for the window was the best purchase I made. Stops you worrying when the day started out cold and you left it all shut up, then while you are out/at work you realise it's got really hot. In the summer in this country I leave the door open all the time and even so it can get really warm and the window opening when it needs to works really well. In spring/autumn I open the door on warm days but know the window will open if it get's to warm or when I haven't opened the door. Then in winter I wind the adjustment of the auto-opener to only open if it get's really warm and keep the door shut.

Which brings me on to ventilation/air flow. You may need to consider some sort of ventilation system, but with a 6'x6' you may not depending on where you site it. Mine get's a strong breeze between two buildings and just an open window is enough for the air flow to stop mold/fungus, but in the winter it can get a bit more stuffed up in there and I worry about air flow. Generally the orchids have coped but I think I have had some mold/fungus problems that I can blame on it being shut up with no air flow for too many days in a row.

[Fairorchids]

Once you have the greenhouse, the bacillus orchiditis takes hold. If you can, squeeze in a 2.4 x 3,.0; you can fit so many more babies in there. Or maybe a 3.0 x 3.6. Actually, a 3.0 x 6.0 . . .