If you are using any type of single layer tin sheeting on a roof you will always have an issue with condensation. I use sheets for many jobs and recommend them to clients too. I particularly like their pan tile sheets, these look good and make a new building blend in well. On the condensation issue with non insulated sheets; If you put a breathable membrane such as Tyvec in as an under layer you will remove the condensation issue. Put this layer in over your rafters and then counter batten ready for the Cladco sheets, problem solved! Reason I like Tyvec is that it is grey underside and white topside unlike the competition thus giving a more pleasant view from underneath. Remember to pull the Tyvec tight and a staple gun helps fix this to the rafters. You can use clear sheets for light too and a perspex sheet can be fixed underneath to provide the condensation barrier. A bit like secondary double glazing. codlasher