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
Featured articles and news
The Association of Consultant Architects recap
A reintroduction and recap of ACA President; Patrick Inglis' Autumn update.
The Home Energy Model and its wrappers
From SAP to HEM, EPC for MEES and FHS assessment wrappers.
Future Homes Standard Essentials launched
Future Homes Hub launches new campaign to help sector prepare for the implementation of new building standards.
Building Safety recap February, 2026
Our regular run-down of key building safety related events of the month.
Planning reform: draft NPPF and industry responses.
Last chance to comment on proposed changes to the NPPF.
A Regency palace of colour and sensation. Book review.
Delayed, derailed and devalued
How the UK’s planning crisis is undermining British manufacturing.
How much does it cost to build a house?
A brief run down of key considerations from a London based practice.
The need for a National construction careers campaign
Highlighted by CIOB to cut unemployment, reduce skills gap and deliver on housing and infrastructure ambitions.
AI-Driven automation; reducing time, enhancing compliance
Sustainability; not just compliance but rethinking design, material selection, and the supply chains to support them.
Climate Resilience and Adaptation In the Built Environment
New CIOB Technical Information Sheet by Colin Booth, Professor of Smart and Sustainable Infrastructure.
Turning Enquiries into Profitable Construction Projects
Founder of Develop Coaching and author of Building Your Future; Greg Wilkes shares his insights.
IHBC Signpost: Poetry from concrete
Scotland’s fascinating historic concrete and brutalist architecture with the Engine Shed.
Demonstrating that apprenticeships work for business, people and Scotland’s economy.
Scottish parents prioritise construction and apprenticeships
CIOB data released for Scottish Apprenticeship Week shows construction as top potential career path.
From a Green to a White Paper and the proposal of a General Safety Requirement for construction products.
Creativity, conservation and craft at Barley Studio. Book review.
The challenge as PFI agreements come to an end
How construction deals with inherited assets built under long-term contracts.
Skills plan for engineering and building services
Comprehensive industry report highlights persistent skills challenges across the sector.
Choosing the right design team for a D&B Contract
An architect explains the nature and needs of working within this common procurement route.
Statement from the Interim Chief Construction Advisor
Thouria Istephan; Architect and inquiry panel member outlines ongoing work, priorities and next steps.