Alternatives to Glass for Greenhouses

Hi all,

Have a quick question about my pre-winter greenhouse maintenance and this looks like a friendly corner of the internet! My greenhouse is looking a little worse for wear - a couple of panels have had cracks in for ages, one of them is shattered thanks to an unfortunately accurate cricket ball and most of the glass is covered in moss and such.

I was snooping around on the internet for some decent tips and stumbled across the idea of replacing the glass with plastic greenhouse panels. It looks as though acrylic or polycarbonate will be stronger, easier to maintain and clearer than glass. What do you all think?

 

How long before the sun's rays start to turn the plastic opaque? If cheap enough you can replace panels every so often.

Cheers, Tony.

 

Hi Tony, yes this was my concern too. The sheet plastic is UV stabilised, but how long they last I'm not so sure. Maybe someone else will know more about these kinds of plastics?

 

Hi Chris
Get a bowl of warm soapy water and a broom,give the glass a good scrub.
I have just done mine,three new panels 24"x 24"....£15 cash.
Good as new........

 

I'm sceptical.

My glass greenhouse gets covered in algae, moss and something hard to remove that Pidgeons sitting on the ridge leave behind :( I struggle to believe that Polycarb won't get just as dirty.

It all comes off with the pressure washer in Autumn, and the glass looks as good as new.

Polycarb is flexible, that causes it to "lift" like a wing in the wind, and then pop out - then the wind gets under the whole structure and the resulting damage is significant of course. Polycarb greenhouse structural members tend to be built of much lighter weight materials - because the polycarb is light - which compounds the "blow away" problem. (Obviously not an issue if you are recladding an existing glasshouse).

The solution to this tends to be to silicon the Polycarb panels in, but that makes their removal an absolute nightmare. Hopefully you never need to do it ... but if you want to get rid of the greenhouse, or replace a bust panel, the job is harder - you'd have no second-hand value (and even if you don't want money for it, someone who will "disassemble and take away" is better than having to "skip" it yourself.

Polycarb probably has better insulation in winter (although if you also use Bubblewrap, which would be essential cost-wise if you are going to heat the greenhouse, then the difference betwen Glass and Polycarb is probably insignificant next to the gain of bubblewrap)

Polycarb also resilient to yobs chucking stones, and kids on bikes misjudging the final hairpin on the course!; for that worry its also worth considering toughened glass.

 

All brilliant suggestions thanks guys.
Would you think glass and bubble wrap is a better insulator than twin wall polycarbonate? Just throwing that one out there...

 

Twin wall polycarbonate seems to be pretty good stuff, and a great insulator too. Me and the Other Half used to use bubble wrap but it looks a bit scruffy and cuts light admittance after a while because it doesn't hold up to high levels of UV.

I'd suggest the OP goes for it with those plastic greenhouse panels, but if you're heating the greenhouse or have harsh winters I'd go for the twin wall. Where are you from?

 

Do I smell a bit of SPAM in this thread.....?
There is no long term substitute for glass in a greenhouse imho.

 

Its not a "great" insulator.

Glass with Bubble-wrap is a better insulator than standard twin wall Polycarb, but you can then can take the bubble wrap down in the Spring and get the benefit of the extra light transmission that glass has, compared to Polycarb..

If it is planned to heat a greenhouse (i.e. to make a warm/hot house, rather than just emergency heating to keep it cool/frost proof) then better still would be to use one of the proprietary glasses that have very good heat retention - they are better than Polycarb even without bubblewrap.

But before going to that extreme there are other steps that will reduce heating costs:

Plant / erect a windbreak. Reducing airflow over a greenhouse can dramatically reduce heating costs. Particularly on the North side of the greenhouse - which is likely to bring colder winders, and a screen [on the North side] has no impact on light

Similarly: fit insulation to the North end of the greenhouse (no light coming through that wall so can use highly efficient, solid, builders insulation).

Make it airtight - reducing the number of air-changes per hour also reduces heating cost significantly. (If using Bubble wrap make sure that the joints are "air tight" - e.g. by using sticky tape to secure them.

Install a "thermal curtain" (or whatever it is called). A curtain just above the plants (e.g. 5' - 6') supported on horizontal wires and which can be "drawn" at night. Doesn't have to transmit light, so can be designed for thermal efficiency without regard to light transmission (and the plants won't mind being under it, in the dark, for several days during really cold winter weather). Also has the benefit of letting through 100% of the light (when it is open!) unlike, say, bubble wrap.

There may be other reasons to fit Polycarb - safety for kids etc., light weight and thus cheaper frames - but its a compromise. Poorer light transmission, discolouration over time, its flexibility means it can "bow" with fast winds blowing over it, and then "pop out", and its blinking noisy when it rains - but that's probably only a consideration for a conservatory not a greenhouse!

Large commercial greenhouses are glass ...

 

Sorry, didn't see this until now.

U-Values (lower = better thermal properties):

Single glass = 1.1
With bubble wrap lining 0.6

Double-wall Polycarb 4mm = 0.7, 6mm = 0.62

So "yes" is the simple answer, but I'm sure there are thicker / better insulating Polycarbs, as there are brands of glass with better thermal properties.

If insulation is your only concern then Glass + Winter bubble wrap gives you the ultimate for light transmission the rest of the time.

 

Oh dear, from who?

Thanks for all the great advice all, I thought I was sold on twin wall polycarbonate but now I'm not so positive! Really I just want to make my greenhouse winter-proof so the maintenance on it isn't such a drain on my finances....will go away and do some more research I think (likely in the office when the boss isn't looking!)

@ Kristen - like the idea of a windbreak, will think more about this because it could work in my garden. I could plant some screening plants along the northside...wouldn't cut out any light and if I insulate it well enough it should be ok...hmm

So much to consider!

 

The spam link was removed from the post, I think, by Abby Black