just finished mine,kglass roof argon gas filled (?) 1.5meter walls each end insulated and 8″ of insulation in the floor nice big rad no doors or windows in the way as i took them out to have it open planned 4.2 mts long 3mts deep and planning regs went to where the sun dont shine,house is as warm as toast out there every night watching telly blinds needed as south facing having the fitted now 3.5k(ouch)