Building envelope
According to Approved Document L2B: conservation of fuel and power in existing buildings other than dwellings, the term 'building envelope' refers to:
| ...the walls, floor, roof, windows, doors, roof windows and roof lights. |
Together, these form the physical separation between the interior and exterior, that is, the climatic modifier that creates and contains the internal conditions.
The nature of the building envelope is likely to depend on a wide range of requirements, some of which may be in conflict:
- The type of building.
- Its location and context.
- Its form.
- Regulatory requirements.
- Local climatic conditions.
- The internal conditions required.
- The need for openings, views, security, safety, access, privacy and so on.
- Available materials.
- Structural requirements.
- Building services strategy,
- Sustainability requirements.
- Maintenance and cleaning requirements.
- Rainwater run off.
- Durability, flexibility and expected life.
- The method of construction, deconstructability and recyclability.
- Stylistic requirements.
- Budgetary and time constraints.
NB According to Approved Document L1A:
| The envelope area of a terraced house includes the party wall(s). The envelope area of a flat in a mulit-storey building includes the floors, walls and ceilings which are shared with adjacent flats. |
And, in relation to air permeability:
| The envelope area, or measured part of the building, is the total area of all floors, walls and ceilings bordering the internal volume that is the subject of the pressure test. This includes walls and floors below external ground level. Overall internal dimensions are used to calculate this envelope area and no subtractions are made for the area of the junctions of internal walls, floors and ceilings with exterior walls, floors and ceilings. |
National Calculation Methodology (NCM) modelling guide (for buildings other than dwellings in England) 2013 edition, published by the Department for Communities and Local Government (DCLG), defines ‘envelope area’ as:
|
Area of vertical envelopes (walls) = h * w, where: h = floor to floor height, ie including floor void, ceiling void and floor slab. For top floors, h is the height from floor to the average height of the structural ceiling. w = horizontal dimension of wall. Limits for that horizontal dimension are defined by type of adjacent walls. If the adjacent wall is external, the limit will be the internal side of the adjacent wall. If the adjacent wall is internal, the limit will be half-way through its thickness. NB: Areas of floor, ceilings, and flat roofs are calculated in the same manner as the zone area. Area for an exposed pitched roof (i.e., without an internal horizontal ceiling) will be the inner pitched surface area of the roof. |
Energy Efficiency and Historic Buildings, How to Improve Energy Efficiency, Published by Historic England in 2018, defines the building envelope as:
| The weathertight skin separating the interior of a building from its external environment. It is made up of the roof, walls, windows, doors, floors and foundations; and systems for controlling and disposing of water, including rainwater goods, roof coverings, damp-proof courses and drains). |
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Local leaders gain new powers to support local high streets
High Street Rental Auctions to be introduced from December.
Infrastructure sector posts second gain for October
With a boost for housebuilder and commercial developer contract awards.
Sustainable construction design teams survey
Shaping the Future of Sustainable Design: Your Voice Matters.
COP29; impacts of construction and updates
Amid criticism, open letters and calls for reform.
The properties of conservation rooflights
Things to consider when choosing the right product.
Adapting to meet changing needs.
London Build: A festival of construction
Co-located with the London Build Fire & Security Expo.
Tasked with locating groups of 10,000 homes with opportunity.
Delivering radical reform in the UK energy market
What are the benefits, barriers and underlying principles.
Information Management Initiative IMI
Building sector-transforming capabilities in emerging technologies.
Recent study of UK households reveals chilling home truths
Poor insulation, EPC knowledge and lack of understanding as to what retrofit might offer.
Embodied Carbon in the Built Environment
Overview, regulations, detail calculations and much more.
Why the construction sector must embrace workplace mental health support
Let’s talk; more importantly now, than ever.
Ensuring the trustworthiness of AI systems
A key growth area, including impacts for construction.
Foundations for the Future: A new model for social housing
To create a social housing pipeline, that reduces the need for continuous government funding.
Mutual Investment Models or MIMs
PPP or PFI, enhanced for public interest by the Welsh Government.
Key points and relevance to construction of meeting, due to reconvene.