An attic or a loft is a space found directly below the pitched roof of a house or other building (also called garret or sky parlor). As attics fill the space between the ceiling of the top floor of a building and the slanted roof, they are known for being awkwardly shaped spaces with exposed rafters and difficult-to-reach corners.
Attics can also help control temperature in a house by providing a large mass of slowly moving air. Hot air rising from lower floors of a building often gets retained in the attic, further compounding their reputation as inhospitable environments. However, in recent years many attics have been insulated to help decrease heating costs since on average, uninsulated attics account for 15% of the total energy loss in an average house.
Modern building codes require unoccupied attics to be ventilated to reduce the accumulation of heat and moisture that contribute to mold growth and decay of wood rafters and ceiling joists.
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% or more of the vent area located in the upper portion of the attic. Various types of turbine ventilators and exhaust fans can also be used to assist with attic ventilation and decrease the required area of passive ventilators.