When constructing a warm roof, the ridged insulation is laid above timber joist and between the sub deck and roof deck. Ventilation is not acquired as there is no air space between the roof and the warm air this prevents any build-up of condensation. The simplicity of the warm roof makes it the most popular design for affectively insulating a flat roof. Through this method there is little or no cold bridging while ensuring there is no unnecessary heat loss. The advantage to this is it saves money on heating costs. This is the best and most comonly used flat roof design for Irish climate.