The role of slope shape roofs in heating energy consumption Based on energy gain

In the past, thermal comfort was achieved through building design and some of construction equipment, and choosing a suitable shell form was one of the favored methods in architecture. These circumstances changed in 1960s and heating, cooling and lighting of the buildings through mechanical equipment achieved a key and pivotal role. Following energy crisis which resulted, paying attention to the building design turned once again to the best heating and cooling method. In addition, Iran's geographical position makes it possible to obtain a considerable amount of radiant energy. In such circumstances, designing architectural components of the building properly can lead to a reduction in its energy consumption. Among these components, roof, which plays a major role in receiving energy and consequently the thermal comfort of the building, is ignored. The study discusses four common types of the roof in cold and dry climates (Karaj), including flat, one-way, two-way and four-way with different angles. Research Methodology is based on modeling and simulation, and the main goal of the study is to achieve optimum form and slope of the roof according to the mean radiant temperature, which is one of the major factors in thermal comfort. The results represent most optimal roof and its optimum angle in sloping ceiling with fixed floor area, according to the energy gain in the surveyed models.