joists. In cold climates ventilation also helps to prevent ice-dams on the roof and leaks that they cause. In hot climates, ventilation reduces cooling loads. Sometimes an insulated roof with an internal vapor barrier is preferable to a ventilated attic. In areas with wildfire hazards, sparks can enter attic vents, so houses are safer without vents. Areas with wind-driven rain, fog or sea-spray might also prefer houses with insulated roofs instead of vents. A habitable attic, or a habitable room without an attic may use an insulated roof so that moist air from the habitable area cannot condense on the roofing materials. Also, a building with a complex roof or many piercings between the conditioned area and the attic might control condensation better or more cheaply with an insulated roof and a vapor barrier. One common code requirement is that the total area of attic vents be equal to or greater than 1/150 of the floor area of the attic, with 50 percent or more of the vent area located in the upper portion of the attic. Vents and louvers should face away from prevailing winds to keep out driven rain. Soffit vents under the eaves normally provide the low vents. Louvered vents in gables can provide the high vents in small houses or short gables. If a ridge is open, some metal roofing systems can install ridge vents along the entire ridge line of the roof. Various types of turbine ventilators and exhaust fans can assist with attic ventilation and decrease the required area of passive ventilators. See also Attic ladder Basement Garret Hayloft Loft Penthouse apartment References External links Rooms