The physical components of the envelope include the foundation, roof, walls, doors, windows, ceiling, and their related barriers and insulation. Hence, air control includes the control of windwashing (cold air passing through insulation) and convective loops which are air movements within a wall or ceiling that may result in 10% to 20% of the heat loss alone. Control of air movement includes flow through the enclosure (the assembly of materials that perform this function is termed the air barrier system) or through components of the building envelope (interstitial) itself, as well as into and out of the interior space, (which can affect building insulation performance greatly). Basement waterproofing and drainage keep the walls dry and a moisture barrier is needed under the floor.Ĭontrol of air flow is important to ensure indoor air quality, control energy consumption, avoid condensation (and thus help ensure durability), and to provide comfort. Moisture can enter basements through the walls or floor. Generally most materials will not remain sealed over the long term and this system is very limited, but ordinary residential construction often treats walls as sealed-surface systems relying on the siding and an underlayment layer sometimes called housewrap. Sealed-surface walls do not allow any water penetration at the exterior surface of the siding material. Drainage walls may also be ventilated to aid drying such as rainscreen and pressure equalization wall systems. Drainage walls allow water that leaks into the wall to drain out such as cavity walls. Barrier walls are designed to allow water to be absorbed but not penetrate the wall, and include concrete and some masonry walls. Types of wall systems with regard to water penetration are barrier, drainage and surface-sealed walls. Walls do not get as severe water exposure as roofs but still leak water. Domestic roof construction may also be ventilated to help remove moisture from leakage and condensation. Typically residential, pitched roofs are covered with an underlayment material beneath the roof covering material as a second line of defense. Pitched roofs are designed to shed water but not resist standing water which can occur during wind-driven rain or ice damming. Flat roofs actually slope up to 10° or 15° but are built to resist 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).
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.
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