When choosing a conservatory, one should always take into consideration the best material for thermal isolation. Set with the choice between: metal, alluminium, PVC or wood, to this day wood, is still by far the best. In the cold wheather, it does not attract condensation and in hot sunshine, it will not transmit heat to the inside. The English by tradition have always built their greenhouses and conservatories in wood under a waterproofcovering of glass and metal.
Those of us who have never lived in old period houses do not realise how old wooden doors and windows really are, in most cases they are the original, installed when the building was built, (more then 100 years).