Flat roofs actually slope up to 10° or 15° but are built to resist intrusion from standing water. Two broad categories of roofs are flat and pitched.

One of the main purposes of a roof is to resist water. Water and water vapor control Ĭontrol of rain is most fundamental, and there are numerous strategies to this end, namely, perfect barriers, drained screens, and mass / storage systems. The control function is at the core of good performance, and in practice focuses, in order of importance, on rain control, air control, heat control, and vapor control. Finish (to meet desired aesthetics on the inside and outside).Control (the flow of matter and energy of all types).Support (to resist and transfer structural and dynamic loads).The many functions of the building envelope can be separated into three categories: Building envelope design is a specialized area of architectural and engineering practice that draws from all areas of building science and indoor climate control. The building envelope (or the more modern term, building enclosure) is all of the elements of the outer shell that maintain a dry, heated, or cooled indoor environment and facilitate its climate control. For example, a holistic energy efficient building design approach can reduce the size of mechanical systems compensating the additional cost of energy efficiency features.A building envelope is the physical separator between the conditioned and unconditioned environment of a building including the resistance to air, water, heat, light, and noise transfer. Energy efficiency approaches sometimes might not require additional capital investment. Air tightness and infiltration of building envelopes are discussed as they play a crucial role in the energy consumption of a building. Application of thermal mass as an energy saving method is more effective in places where the outside ambient air temperature differences between the days and nights are high. The effects of thermal mass and phase change material on building cooling/heating loads and peak loads are discussed. Various types of thermal insulation materials are enumerated along with selection criteria of these materials.

Advances in energy efficient roofs including the contemporary green roofs, photovoltaic roofs, radiant-transmittive barrier and evaporative roof cooling systems are discussed. Performance of different fenestration technologies including aerogel, vacuum glazing and frames are presented. Different types of energy efficient walls such as Trombe walls, ventilated walls, and glazed walls are discussed. This article strives to make an exhaustive technical review of the building envelope components and respective improvements from an energy efficiency perspective. Due to environmental concerns and the high cost of energy in recent years there has been a renewed interest in building energy efficiency. In many of these buildings, the energy consumption can be significantly reduced by adopting energy efficiency strategies. A significant portion of the total primary energy is consumed by today's buildings in developed countries.

Components of building envelope