outside protection for growies

Hi guys, newbie here!

I've had a caterpillar tunnel on my allotment for 3-4 years but any snowfall just collapses it and the plastic is quite badly degraded already.

My priority is growing tomatoes, egg-plant, peppers etc. in the summer but I move it over some established crops in the autumn (broad beans etc.) to give them extra protection over winter.

I'm considering buying ultra-fine insect mesh as an alternative cover - will allow rainfall and air to permeate but still retain heat (I hope; Grok has been quite useful in my research and suggests that this mesh might provide up to 50% of the heat-capture compared to polythene but would not expose me to the problem of overheating (I'm 100ft above sea level in SE Wales so not too much of a problem!)

Any thoughts please?

Nick.

Hi Nick - welcome to permies!
Yes the problem with (cheap) polythene is that it doesn't last very well outside. Proper polytunnel plastic is much more durable, but does also need to be fixed well to get the best advantage.
I think that the mesh materials have several advantages, but as always 'it depends'. It will keep the wind off, reduce the sunlight on the plants and also potentially act as an insect barrier (which can be a good or a bad thing!). I'm not convinced that it will hold onto enough heat to make a difference enough to compensate for the lack of sunshine it might cause though.
You could do a trial maybe with a small amount. Get some polythene just for this year (some reused packaging material would be OK for a season in the UK I should think and free) and get a small amount of the mesh you're thinking of and see whether one does better than the other.
In South Wales you could try tomatoes at least outside too - get some early season ones, or Scottish bred and you may be able to get a crop. I'm not sure about Aubergines though.
Using stones to give reflected/absorbed heat on a South facing wall is one way of creating a favourable microclimate without using plastic. Reusing old windows leaning in a tent like form would be another alternative. Maybe others have more suggestions.