Building envelope
Encyclopedia
The building envelope is the physical separator between the interior and the exterior environments of a building
. Another emerging term is "Building Enclosure". It serves as the outer shell to help maintain the indoor environment (together with the mechanical conditioning systems) and facilitate its climate control. 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 many functions of the building envelope can be separated into three categories :
The control function is at the core of good performance, and in practise focuses, in order of importance, on rain control, air control, heat control, and vapor control.
Control of rain is most fundamental, and there are numerous strategies to this end, namely, perfect barriers, drained screens, and mass / storage systems.
Control of air flow is important to ensure indoor air quality, control energy consumption, avoid condensation (and thus help ensure durability), and to provide comfort. 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). Hence, air control includes the control of windwashing and convective loops.
The physical components of the envelope include the foundation
, roof
, wall
s, door
s and window
s. The dimensions, performance and compatibility of materials, fabrication process and details, their connections and interactions are the main factors that determine the effectiveness and durability of the building enclosure system.
Common measures of the effectiveness of a building envelope include physical protection from weather and climate (comfort), indoor air quality (hygiene and public health), durability and energy efficiency. In order to achieve these objectives, all building enclosure systems must include a solid structure, a drainage plane, an air barrier, a thermal barrier, and may include a vapor barrier. Moisture control is essential in all climates, but cold climates and hot-humid climates are especially demanding. See damp proofing
, dew point
, condensation
, and toxic mold
.
The thermal envelope (or heat flow control layer) is usually different than the building envelope. The difference can be illustrated by understanding that an insulated attic floor is the primary thermal control layer between the inside of the house and the exterior while the entire roof (from the surface of the shingles to the interior paint finish on the ceiling) comprises the building envelope.
Building Envelope Thermography
involves using an infrared camera to view temperature anomalies on the interior and exterior surfaces of the structure. Analysis of infrared images can be useful in identifying moisture issues from water intrusion, or internal condensation. Shown below is an example of an image within the scope of a residential infrared inspection in which an uninsulated HVAC plenum was located in a confined attic space. The humidity from the warm attic air condensed on the plenum and was damaging the ceiling and walls.
In a city planning and zoning context, the "building envelope" can be 'the three dimensional space created by the designated setbacks and height restrictions in place for a zoning district.
Building
In architecture, construction, engineering, real estate development and technology the word building may refer to one of the following:...
. Another emerging term is "Building Enclosure". It serves as the outer shell to help maintain the indoor environment (together with the mechanical conditioning systems) and facilitate its climate control. Building envelope design is a specialized area of architectural and engineering practice that draws from all areas of building science
Building science
Building science is the collection of scientific knowledge that focuses on the analysis and control of the physical phenomena affecting buildings. It traditionally includes the detailed analysis of building materials and building envelope systems...
and indoor climate control.
The many functions of the building envelope can be separated into three categories :
- Support (to resist and transfer mechanical loads)
- Control (the flow of matter and energy of all types)
- Finish (to meet human desires on the inside and outside)
The control function is at the core of good performance, and in practise focuses, in order of importance, on rain control, air control, heat control, and vapor control.
Control of rain is most fundamental, and there are numerous strategies to this end, namely, perfect barriers, drained screens, and mass / storage systems.
Control of air flow is important to ensure indoor air quality, control energy consumption, avoid condensation (and thus help ensure durability), and to provide comfort. 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
Building insulation
building insulation refers broadly to any object in a building used as insulation for any purpose. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation...
performance greatly). Hence, air control includes the control of windwashing and convective loops.
The physical components of the envelope include the foundation
Foundation (architecture)
A foundation is the lowest and supporting layer of a structure. Foundations are generally divided into two categories: shallow foundations and deep foundations.-Shallow foundations:...
, roof
Roof
A roof is the covering on the uppermost part of a building. A roof protects the building and its contents from the effects of weather. Structures that require roofs range from a letter box to a cathedral or stadium, dwellings being the most numerous....
, wall
Wall
A wall is a usually solid structure that defines and sometimes protects an area. Most commonly, a wall delineates a building and supports its superstructure, separates space in buildings into rooms, or protects or delineates a space in the open air...
s, door
Door
A door is a movable structure used to open and close off an entrance, typically consisting of a panel that swings on hinges or that slides or rotates inside of a space....
s and window
Window
A window is a transparent or translucent opening in a wall or door that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material like float glass. Windows are held in place by frames, which...
s. The dimensions, performance and compatibility of materials, fabrication process and details, their connections and interactions are the main factors that determine the effectiveness and durability of the building enclosure system.
Common measures of the effectiveness of a building envelope include physical protection from weather and climate (comfort), indoor air quality (hygiene and public health), durability and energy efficiency. In order to achieve these objectives, all building enclosure systems must include a solid structure, a drainage plane, an air barrier, a thermal barrier, and may include a vapor barrier. Moisture control is essential in all climates, but cold climates and hot-humid climates are especially demanding. See damp proofing
Damp proofing
Damp proofing in construction is a type of waterproofing applied to building foundation walls to prevent moisture from passing through the walls into interior spaces....
, dew point
Dew point
The dew point is the temperature to which a given parcel of humid air must be cooled, at constant barometric pressure, for water vapor to condense into liquid water. The condensed water is called dew when it forms on a solid surface. The dew point is a saturation temperature.The dew point is...
, condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, and toxic mold
Toxic mold
Mold health issues are potentially harmful effects of molds.Molds are ubiquitous in the biosphere, and mold spores are a common component of household and workplace dust...
.
The thermal envelope (or heat flow control layer) is usually different than the building envelope. The difference can be illustrated by understanding that an insulated attic floor is the primary thermal control layer between the inside of the house and the exterior while the entire roof (from the surface of the shingles to the interior paint finish on the ceiling) comprises the building envelope.
Building Envelope Thermography
Thermography
Infrared thermography, thermal imaging, and thermal video are examples of infrared imaging science. Thermal imaging cameras detect radiation in the infrared range of the electromagnetic spectrum and produce images of that radiation, called thermograms...
involves using an infrared camera to view temperature anomalies on the interior and exterior surfaces of the structure. Analysis of infrared images can be useful in identifying moisture issues from water intrusion, or internal condensation. Shown below is an example of an image within the scope of a residential infrared inspection in which an uninsulated HVAC plenum was located in a confined attic space. The humidity from the warm attic air condensed on the plenum and was damaging the ceiling and walls.
In a city planning and zoning context, the "building envelope" can be 'the three dimensional space created by the designated setbacks and height restrictions in place for a zoning district.
External links
- Training Material (software, presentation slides, e-textbook, case studies, templates) on Building Envelope from RETScreen International
- Ontario Building Envelope Council
- British Columbia Building Envelope Council
- Alberta Building Envelope Council-South Chapter
- Pushing the Envelope: Building Sciences Journal