Building envelope

Short description: Concept in architectural and engineering practice

A building envelope or building enclosure is the physical separator between the conditioned and unconditioned environment of a building, including the resistance to air, water, heat,[1] light, and noise[2] transfer.

## Contents

* 1 Discussion
* 2 Water and water vapor control
* 3 Air control
* 4 Thermal envelope
* 5 See also
* 6 References
* 7 External links

## Discussion

The building envelope or enclosure is all of the elements of the outer shell that maintain a dry, heated, or cooled indoor environment 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.[2]

The many functions of the building envelope can be separated into three categories:[3]

* Support (to resist and transfer structural and dynamic loads)
* Control (the flow of matter and energy of all types)
* Finish (to meet desired aesthetics on the inside and outside)

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.[3]

## Water and water 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.[4]

One of the main purposes of a roof is to resist water. Two broad categories of roofs are flat and pitched. Flat roofs actually slope up to 10° or 15° but are built to resist intrusion from standing water. Pitched roofs are designed to shed water but not resist standing water intrusion which can occur during wind-driven rain or ice damming. Typically residential, pitched roofs are covered with an underlayment material beneath the roof covering material as a second line of defense. Domestic roof construction may also be ventilated to help remove moisture from leakage and condensation.[citation needed]

Walls do not get as severe water exposure as roofs but still leak water. Types of wall systems with regard to water penetration are barrier, drainage and surface-sealed walls.[5] Barrier walls are designed to allow water to be absorbed but not penetrate the wall, and include concrete and some masonry walls. Drainage walls allow water that leaks into the wall to drain out such as cavity walls. Drainage walls may also be ventilated to aid drying such as rainscreen and pressure equalization wall systems. Sealed-surface walls do not allow any water penetration at the exterior surface of the siding material. 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.[citation needed]

Moisture can enter basements through the walls or floor. Basement waterproofing and drainage keep the walls dry and a moisture barrier is needed under the floor.[citation needed]

## Air control

Main article: Engineering:Air barrier

Control of airflow 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[6] (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.[7]

The physical components of the envelope include the foundation, roof, walls, doors, windows, ceiling, and their related barriers and insulation. The dimensions, performance and compatibility of materials, fabrication process and details, connections and interactions are the main factors that determine the effectiveness and durability of the building enclosure system.[citation needed]

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 (e.g. damp proofing) is essential in all climates, but cold climates and hot-humid climates are especially demanding.[8]

Air sealing can improve the energy efficiency of a building by minimizing the amount of energy needed to heat or cool the building. This is especially pertinent in cold-climate buildings where space heating consumes the largest amount of energy.[9] A blower door test can be used to evaluate and measure the quality of the air sealing of the building envelope. Smoke pencils can be used to detect gaps and caulking and weather-stripping can be used to improve air sealing.[10] HVAC systems can ensure that a building’s air intake is both adequate, safe, and energy efficient.

## Thermal envelope

The thermal envelope, or heat flow control layer, is part of a building envelope but may be in a different location such as in a ceiling. The difference can be illustrated by the fact 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 roofing material to the interior paint finish on the ceiling) is part of the building envelope.[11]

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 interstitial condensation.[12] Other types of anomalies that can be detected are thermal bridging, continuity of insulation and air leakage, however this requires a temperature differential between the inside and outside ambient temperatures.[13]

The design of the thermal envelope, particularly the external façades, plays a critical role in mediating the urban microclimate, not just the interior conditions. Research analyzing different façade systems (traditional, lightweight, and external thermal insulation composite systems) has shown that façade thermal mass is the primary factor affecting ambient air temperature (AT), with high-mass systems leading to greater cooling of the surrounding air. Conversely, the albedo (reflectivity) of the façade surface primarily influences the Mean Radiant Temperature (MRT). In dense urban canyons, high-albedo surfaces can be counterproductive, significantly increasing the MRT due to multiple reflections, thereby increasing thermal stress in the immediate outdoor environment.[14]

## See also

* Engineering:Architectural engineering - Engineering discipline of engineering systems of buildings
* Engineering:Mechanical engineering - Engineering discipline
* Engineering:Structural engineering - Sub-discipline of civil engineering dealing with the creation of man made structures

## References

1. ↑ Cleveland, Cutler J., and Christopher G. Morris. Building envelopergy. Expanded Edition. Burlington: Elsevier, 2009. Print.
2. ↑ 2.0 2.1 Syed, Asif. Advanced building technologies for sustainability. Hoboken, N.J.: John Wiley & Sons, Inc., 2012. 115. Print.
3. ↑ 3.0 3.1 Straube, J.F., Burnett, E.F.P. Building Science for Building Enclosures. Building Science Press, Westford, 2005.
4. ↑ 11\. Straube, J.F. and Burnett, E.F.P., "Rain Control and Design Strategies". Journal of Thermal Insulation and Building Envelopes, July 1999, pp. 41–56.
5. ↑ various authors. Guideline for condition assessment of the building envelope. Reston, Va.: American Society of Civil Engineers, 2000. 4. Print.
6. ↑ Hens, Hugo S. L. C. Performance Based Building Design 2: From Timber-framed Construction to Partition Walls. Berlin: Ernst, William & Son, 2012. 10. Print.
7. ↑ Harrje, D. T, G. S. Dutt and K. J. Gadsby, "Convective Loop Heat Losses in Buildings". Oak Ridge National Laboratory. 1985. Print.
8. ↑ Lstiburek, Joseph W., and John Carmody. Moisture Control Handbook: Principles and Practices for Residential and Small Commercial Buildings. New York: Van Nostrand Reinhold, 1993. 88. Print.
9. ↑ Asaee, S. Rasoul; Sharafian, Amir; Herrera, Omar E.; Blomerus, Paul; Mérida, Walter (May 2018). "Housing stock in cold-climate countries: Conversion challenges for net zero emission buildings" (in en). Applied Energy 217: 88–100. doi:10.1016/j.apenergy.2018.02.135. Bibcode: 2018ApEn..217...88A. https://linkinghub.elsevier.com/retrieve/pii/S0306261918302691.
10. ↑ Canada, Natural Resources (2014-03-06). "Keeping The Heat In - Section 4: Comprehensive air leakage control in your home". https://www.nrcan.gc.ca/energy-efficiency/homes/make-your-home-more-energy-efficient/keeping-the-heat/section-4-comprehensive-air-leakage-control-your-home/15635.
11. ↑ Vliet, Willem. The Encyclopedia of Housing. Thousand Oaks, Calif.: Sage, 1998. 139. Print.
12. ↑ Hunaidi, Osama. Leak Detection Methods for Plastic Water Distribution Pipes. Denver, Colo.: AWWA Research Foundation, 1999. 57. Print.
13. ↑ Faulkner, Ray. Infrared Building Surveys. Portsmouth, United Kingdom: iRed, 2017.
14. ↑ Alchapar, Noelia; Giancola, Emanuela; Pérez Álvarez-Quiñones, Gloria; Terraza, Maira; Pezzuto, Cláudia (2025). "Façade Strategies for Climate Resilience: The Impact of Thermal Mass and Albedo on Urban Microclimates Across Different Climatic Zones". Urban Science 9 (10): 428. doi:10.3390/urbansci9100428. Bibcode: 2025UrbSc...9..428A.

## External links

* Training Material (software, presentation slides, e-textbook, case studies, templates) on Building Envelope - Natural Resources Canada
* Ontario Building Envelope Council
* British Columbia Building Envelope Council
* Alberta Building Envelope Council-South Chapter

* v
* t
* e

Heating, ventilation, and air conditioning

Fundamental concepts|

* Air changes per hour
* Bake-out
* Building envelope
* Convection
* Dilution
* Domestic energy consumption
* Enthalpy
* Fluid dynamics
* Gas compressor
* Heat pump and refrigeration cycle
* Heat transfer
* Humidity
* Infiltration
* Latent heat
* Noise control
* Outgassing
* Particulates
* Psychrometrics
* Sensible heat
* Stack effect
* Thermal comfort
* Thermal destratification
* Thermal mass
* Thermodynamics
* Vapour pressure of water

Technology|

* Absorption refrigerator
* Air barrier
* Air conditioning
* Antifreeze
* Automobile air conditioning
* Autonomous building
* Building insulation materials
* Central heating
* Central solar heating
* Chilled beam
* Chilled water
* Constant air volume (CAV)
* Coolant
* Dedicated outdoor air system (DOAS)
* Deep water source cooling
* Demand-controlled ventilation (DCV)
* Displacement ventilation
* District cooling
* District heating
* Electric heating
* Energy recovery ventilation (ERV)
* Firestop
* Forced-air
* Forced-air gas
* Free cooling
* Heat recovery ventilation (HRV)
* Hybrid heat
* Hydronics
* HVAC
* Ice storage air conditioning
* Kitchen ventilation
* Mixed-mode ventilation
* Microgeneration
* Natural ventilation
* Passive cooling
* Passive house
* Radiant heating and cooling system
* Radiant cooling
* Radiant heating
* Radon mitigation
* Refrigeration
* Renewable heat
* Room air distribution
* Solar air heat
* Solar combisystem
* Solar cooling
* Solar heating
* Thermal insulation
* Underfloor air distribution
* Underfloor heating
* Vapor barrier
* Vapor-compression refrigeration (VCRS)
* Variable air volume (VAV)
* Variable refrigerant flow (VRF)
* Ventilation

Components|

* Air conditioner inverter
* Air door
* Air filter
* Air handler
* Air ionizer
* Air-mixing plenum
* Air purifier
* Air source heat pumps
* Automatic balancing valve
* Back boiler
* Barrier pipe
* Blast damper
* Boiler
* Centrifugal fan
* Ceramic heater
* Chiller
* Condensate pump
* Condenser
* Condensing boiler
* Convection heater
* Compressor
* Cooling tower
* Damper
* Dehumidifier
* Duct
* Economizer
* Electrostatic precipitator
* Evaporative cooler
* Evaporator
* Exhaust hood
* Expansion tank
* Fan coil unit
* Fan filter unit
* Fan heater
* Fire damper
* Fireplace
* Fireplace insert
* Freeze stat
* Flue
* Freon
* Fume hood
* Furnace
* Furnace room
* Gas compressor
* Gas heater
* Gasoline heater
* Geothermal heat pump
* Grease duct
* Grille
* Ground-coupled heat exchanger
* Heat exchanger
* Heat pipe
* Heat pump
* Heating film
* Heating system
* High efficiency glandless circulating pump
* High-efficiency particulate air (HEPA)
* High pressure cut off switch
* Humidifier
* Infrared heater
* Inverter compressor
* Kerosene heater
* Louver
* Mechanical fan
* Mechanical room
* Oil heater
* Packaged terminal air conditioner
* Plenum space
* Pressurisation ductwork
* Process duct work
* Radiator
* Radiator reflector
* Recuperator
* Refrigerant
* Register
* Reversing valve
* Run-around coil
* Scroll compressor
* Solar chimney
* Solar-assisted heat pump
* Space heater
* Smoke exhaust ductwork
* Thermal expansion valve
* Thermal wheel
* Thermosiphon
* Thermostatic radiator valve
* Trickle vent
* Trombe wall
* Turning vanes
* Ultra-low particulate air (ULPA)
* Whole-house fan
* Windcatcher
* Wood-burning stove

Measurement
and control|

* Air flow meter
* Aquastat
* BACnet
* Blower door
* Building automation
* Carbon dioxide sensor
* Clean Air Delivery Rate (CADR)
* Gas sensor
* Home energy monitor
* Humidistat
* HVAC control system
* Intelligent buildings
* LonWorks
* Minimum efficiency reporting value (MERV)
* OpenTherm
* Programmable communicating thermostat
* Programmable thermostat
* Psychrometrics
* Room temperature
* Smart thermostat
* Thermostat
* Thermostatic radiator valve

Professions, trades,
and services|

* Architectural acoustics
* Architectural engineering
* Architectural technologist
* Building services engineering
* Building information modeling (BIM)
* Deep energy retrofit
* Duct leakage testing
* Environmental engineering
* Hydronic balancing
* Kitchen exhaust cleaning
* Mechanical engineering
* Mechanical, electrical, and plumbing
* Mold growth, assessment, and remediation
* Refrigerant reclamation
* Testing, adjusting, balancing

Industry organizations|

* ACCA
* AHRI
* AMCA
* ASHRAE
* ASTM International
* BRE
* BSRIA
* CIBSE
* Institute of Refrigeration
* IIR
* LEED
* SMACNA

Health and safety|

* Indoor air quality (IAQ)
* Passive smoking
* Sick building syndrome (SBS)
* Volatile organic compound (VOC)

See also|

* ASHRAE Handbook
* Building science
* Fireproofing
* Glossary of HVAC terms
* World Refrigeration Day

* Template:Home automation
* Template:Solar energy

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