In message , Duncan Heenan
writes
I am hoping to construct my first ever greenhouse this winter, as a DIY
project, doing my own design & sourcing materials rather than buying a kit.
What I'm wondering is:
1. If I use polycarbonate for the roof (as I'd like to for strength and
lightness), will it let through enough of the light spectrum to be good for
the plants, or do I need to use glass?

It should be ok - Lots of the year GH end up being shaded anyway.

What about something like a Keder house?

http://www.kedergreenhouse.co.uk/

2. Is standard annealed glass OK to use in the windows, or do I have to use
some special 'horticultural glass'? If so, how does horticultural glass
differ from normal glass?

It doesn't 'Hoticultural/greenhouse glass' is just cheaper, normal
glass.

3. Is there any regulation relating to domestic greenhouses which say I have
to use safety glass?

No, leastways not that I'm aware of , never heard of it and standard
retail GH come with normal glass
--
Chris French and Helen Johnson, Leeds
urg Suppliers and References FAQ:
http://www.familyfrench.co.uk/garden/urgfaq/index.html