We have a conservatory which must have the world's worst roof - it is draughty, terrible at keeping in heat in winter and keeping it cool in summer. We have roof blinds fitted which help, but it is expensive to heat and permanently dreary with lack of natural light thought the roof. We intend to replace the whole conservatory as part of a complete overhaul of our home, and would welcome advice as to the best kinds of roof, and some rough prices if possible (the room is 3m x 4m)
Can't advise on price as ours came as a complete conservatory but we have opaque (white but kinda hazy white) twin wall polycarbonate sheets which are superb. They allow loads of light in but shade us from sun inside.
I also use a single 3kw oil filled radiator for heating with a small 6" desk fan attached to it to circulate the heat and this keeps our 5m x 4m conservatory like toast
Agree with andyjefs 100%! Don't get a glass roof, friends did and regreted it - too hot in summer & difficult to keep clean. Mine has an Opal/copper triple walled roof,with an electric 2kw convector,with a 2kw blower to warm up quick!! A 4m x 4m should cost around 8 to 10 thousand pounds, but get at least 3 quotes!!
The material chasbo is referring to is probably polycarbonate - very tough and light (weight). The best polycarbonate now comes quinwall, which has four air layers in it (quad-glazing). Its obvious that the most heat loss (in winter) in these things goes through the roof.