Roofs are the most important element of a house to insulate as heat rises in our rooms and this warm air will cool rapidly when it touches cold roof or ceiling surfaces. It will cause convection and cause cold downward draughts, creating more heat loss and discomfort, especially where high ceilings occur that are poorly insulated. Roof can also emit more heat than walls per surface area, on cold nights with clear sky conditions. You can see the same thing happening on the roof of a car on the morning after a cold night, where condensation or even frost will form on the roof first, even when ambient temperatures are above freezing. Depending on whether a bungalow, two storey or multi-storey building, roofs will contribute differently to heat loss. Relative to a given floor area, a poorly insulated roof of a bungalow will have twice the heat loss of a similar two storey house and three times that of a three-storey house. Typically the average roof contributes 25% of the heat loss through all the external elements. Roofs however are usually easier and much cheaper to insulate than walls.