structural:expansion, structural:summarization
An attic is a space found directly below the pitched roof of a house or other building. It may also be called a sky parlor or a garret. Because they fill the space between the ceiling of a building's top floor and its slanted roof, attics are known for being awkwardly-shaped spaces with difficult-to-reach corners and often exposed rafters. While some attics are converted into bedrooms, home offices, or attic apartments complete with windows and staircases, most remain difficult to access, and are usually entered using a loft hatch and ladder. Attics help control temperatures in a house by providing a large mass of slowly moving air, and are often used for storage. The hot air rising from the lower floors of a building is often retained in attics, further compounding their reputation as inhospitable environments. However, in recent years, they have been insulated to help decrease heating costs, since, on average, uninsulated attics account for 15% of the energy loss in average houses. A loft or mezzanine is also the uppermost space in a building, but is distinguished from an attic in that an attic typically constitutes an entire floor of the building, while a loft or mezzanine covers only a few rooms, leaving one or more sides open to the lower floor. Attics are found in many different shapes and sizes. They also have many uses: In residential buildings, they are either small unusable spaces filled with insulation, or spaces with storage or HVAC equipment. Some commercial buildings also have attics under pitched roofs that are usually used for storage, mechanical equipment, or for roof access.