geoff wrote in message news:bI$I+VDUFHE$Ew2W@
writes

I've also bought some polythene, 36sqm for 15 quid, trouble is it's
not as clear as I hoped and I may not use it, hmmm.

Having forgotten the details here, two points to bear in mind

1/ Polythene doesn't last forever in direct sunlight
2/ If you are talking about using the polythene to allow sunlight in to
heat the pipes, just because something is opaque to visible radiation,
doesn't mean it's not clear to I/R. You might have to ask someone or
look it up

Polytunnel greenhouses heat up same as glass ones, it works. Only lasts a few years.

Regards, NT