Replacing greenhouse glass

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 MG 24 Jan 2021

Are there any reasons I shouldn't use acrylic to replace greenhouse glass?

 Ridge 24 Jan 2021
In reply to MG:

Based on no expertise other than erecting the odd greenhouse under Mrs Ridge's supervision, I think there might be a couple of issues:

1. Glass adds a lot of weight to the structure, so if using all acrylic you might need to beef up the ground anchors. I also suspect it adds s fair bit of rigidity to the structure.

2. Acylic, depending on thickness, probably flexes a bit when wind load is applied. If that's enough to pop the clips you'll lose the panel. If that happens in high winds the other panels tend then to blow out as the greenhouse pressurises inside.

 mutt 24 Jan 2021
In reply to MG:

yes, it doesn't have the same greenhouse effect, i.e reflecting the IR radiation back into the greenhouse as heat. We did this when our first child broke his first pane of the greenhouse with a football. It became just a shed after that with no useful growing capabilities. The acrylic ages pretty quickly and droops so the panes will drop out after a few years, and they will break just as readily with football impacts although the broken bits are less likely to cut anyone who ventures in. 

 Tom Valentine 24 Jan 2021
In reply to Ridge:

I  can't see how glass  adds rigidity when it's only held in place by a few spring clips per pane, unless it's the weight of the roof panes which bears down on the uprights somehow.

Post edited at 19:52
 Ridge 24 Jan 2021
In reply to Tom Valentine:

Fair point. There certainly is a difference in the rigidity of a glazed vs unglazed structure though. I suppose it could maybe be purely down to friction between the frame and the clipped in glass panels.

 Tom Valentine 24 Jan 2021
In reply to Ridge:

maybe you are used to  structures where the glass and frame fit can be measured in terms of 2 or 3 mm: not the case in my greenhouse.

 Ridge 24 Jan 2021
In reply to Tom Valentine:

That might be it. Not precision engineered in any sense, but 5mm out would mean the panels wouldn't fit.

 Tom Valentine 24 Jan 2021
In reply to Ridge:

The extra is in the frame so the glass panes typically have  up to 5 mm space each/ either side. That's why i can't see them contributing to the overall rigidity.

Post edited at 20:30
OP MG 24 Jan 2021
In reply to Ridge:

Good point about the weight.  Will consider.

OP MG 24 Jan 2021
In reply to mutt:

> yes, it doesn't have the same greenhouse effect, i.e reflecting the IR radiation back into the greenhouse as heat.

Interesting.  Will look in to that.  Plastic sellers (of course) insist it works.  Polycarbonate is another expensive option.  Or glass of course but it isn't that easy to get these days I am finding.

 RobAJones 24 Jan 2021
In reply to MG:

> Interesting.  Will look in to that.  Plastic sellers (of course) insist it works.  Polycarbonate is another expensive option.  Or glass of course but it isn't that easy to get these days I am finding.

Our greenhouses are in quite an exposed position, after a few years ofregularly losing glass panes I bought some polycarbonate sheets 600*300. They weren't cheap £50 for 10 sheets about 15 years ago. They are still there, the greens houses are fixed to a breeze block base and as the sheets are easy to drill through you can fix them to wooden battens. They have discoloured a bit over the years so don't look great, but we haven't noticed any reduction in their productivity.

OP MG 24 Jan 2021
In reply to RobAJones:

I was looking at polycarbonate was getting £45 per sheet, so stopped!!

 RobAJones 24 Jan 2021
In reply to MG:

It was something like this

https://www.roofingsuperstore.co.uk/product/marlon-4mm-horticultural-insula...

I got my sizes wrong 1200*600 fits instead of two 600*600 pieces of glass 

OP MG 24 Jan 2021
In reply to RobAJones:

Thanks!

 Baron Weasel 25 Jan 2021
In reply to MG:

Twin wall polycarbonate is great, I've got a second greenhouse to build and I'll use it again. It's much safer than glass with kids around and the temperature is more stable at night which is good for starting plants early season. 

 mutt 26 Jan 2021
In reply to MG:

possibly worth also noting that introducing more plastic to the world is probably not what we want t be doing.  

OP MG 26 Jan 2021
In reply to mutt:

> possibly worth also noting that introducing more plastic to the world is probably not what we want t be doing.  

In general I agree but long term applications seem much more defensible to me than single use, particularly when they will also reduce food waste and miles. That said, I am coming back to glass,.having found a source.

 mutt 26 Jan 2021
In reply to MG:

good to hear. glass is the best choice. 

 John Workman 26 Jan 2021
In reply to MG:

I misread this as replacing greenhouse gas - which sounded interesting. Bit of a disappointment.

 David Riley 26 Jan 2021
In reply to MG:

When I bought my house there was a half built wooden greenhouse in the garden that had stood out for years and never been glazed.  I finished it with polycarbonate pre-cut shapes from www.polycarbdirect.co.uk .  Still good 7 years later.


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