Performance gap between building design and operation
There is significant evidence to suggest that buildings do not perform as well when they are completed as was anticipated when they were being designed. The difference between anticipated and actual performance is known as the performance gap.
Findings from studies such as PROBE (Post Occupancy Review of Buildings and their Engineering) which assessed 23 buildings previously featured as ‘exemplar designs’ in the Building Services Journal between 1995 and 2002, revealed that actual energy consumption in buildings is often twice as much as predicted.
More recent studies have suggested that in-use energy consumption can 5 to 10 times higher than compliance calculations carried out during the design stage:
- The Zero Carbon Hub Closing the gap between design and as-built performance, Evidence review report.
- Innovate UK's Building Performance Evaluation Programme.
- The Carbon Trust‘s Closing the gap, Lessons learned on realising the potential of low carbon building design.
- Carbon Buzz, Performance gap benchmarking data.
Studies such as these suggest that factors contributing to the performance gap include:
- A lack of monitoring and feedback following occupancy, meaning that problems are rarely identified, user behaviour is not corrected and lessons are not learned for future projects.
- Design assumptions do not properly reflect the in-use performance of buildings.
- Designers are rarely required to predict actual in-use energy consumption.
- Calculations for regulatory compliance do not account for all energy uses in buildings. These calculations are commonly misinterpreted as predictions of in-use energy consumption, when in fact they are simply mechanisms for complying with the Building Regulations.
- Unregulated sources of energy consumption such as small power loads, server rooms, external lighting, and so on are rarely considered at the design stage. Yet these typically account for more than 30% of the energy consumption in office buildings.
- The lack of guidance for modelling unregulated energy loads makes it difficult for designers to consider these at design stage.
- There are discrepancies between design specification and the specification and quality of works as-built.
- There are incorrect assumptions about the performance of some building components (such as party walls).
- There are rarely any consequences for designers, contractors and suppliers when energy consumption exceeds predictions.
- Project participants struggle to communicate the intended energy performance for the design from the earliest stages, and have ongoing problems with communicating the design intent throughout detailed design.
- There is poor feedback from site about what is, and what is not buildable.
- Site practices that may have been acceptable 20 years ago, no longer meet the required standards.
- There is an absence of engineering rigour around the design and installation of the services.
NB: In November 2015, BSRIA announced that it would back a four-month feasibility study to develop a prototype UK scheme intended to deliver the standard of energy performance specified in client briefs by adopting a ‘design for performance’ approach, first pioneered in Australia. See BSRIA support study into Australian solution to performance gap for more information.
[edit] Related articles on Designing Buildings
- Achieving sustainable futures with thermal imaging.
- Building data exchange.
- Building performance.
- Building performance evaluation programme.
- Building performance metrics.
- Building regulations.
- BREEAM.
- Closing the gap between design and as-built performance.
- Co-heating test.
- Code for sustainable homes.
- Domestic ventilation systems performance.
- Energy performance certificate.
- Energy Savings Opportunity Scheme.
- Facilities management audit FMA.
- Green building.
- Leadership in Energy and Environmental Design.
- Mind the (performance) gap.
- Performance.
- Performance of exemplar buildings in use: Bridging the performance gap FB 78.
- Performance requirements.
- Quad Central in Malta aims for LEED Platinum certification.
- Retrofit, refurbishment and the growth of connected HVAC technology.
- Soft landings.
- Strategic performance targets.
- The effects of subframe systems on the overall thermal performance of external rainscreen walls.
- The history of non-domestic air tightness testing.
- Thermal imaging to improve energy efficiency in building design.
- Why the UK needs to support emerging tech like energy storage.
Featured articles and news
Building Safety Regulator reforms
New roles, new staff and a new fast track service pave the way for a single construction regulator.
Cooling centres and cool spaces
Managing extreme heat in cities by directing the public to places for heat stress relief and water sources.
Winter gardens: A brief history and warm variations
Extending the season with glass in different forms and terms.
Restoring Great Yarmouth's Winter Gardens
Transforming one of the least sustainable constructions imaginable.
Construction Skills Mission Board launch sector drive
Newly formed government and industry collaboration set strategy for recruiting an additional 100,000 construction workers a year.
New Architects Code comes into effect in September 2025
ARB Architects Code of Conduct and Practice available with ongoing consultation regarding guidance.
Welsh Skills Body (Medr) launches ambitious plan
The new skills body brings together funding and regulation of tertiary education and research for the devolved nation.
Paul Gandy FCIOB announced as next CIOB President
Former Tilbury Douglas CEO takes helm.
UK Infrastructure: A 10 Year Strategy. In brief with reactions
With the National Infrastructure and Service Transformation Authority (NISTA).
Ebenezer Howard: inventor of the garden city. Book review.
The Grenfell Tower fire, eight years on
A time to pause and reflect as Dubai tower block fire reported just before anniversary.
Airtightness Topic Guide BSRIA TG 27/2025
Explaining the basics of airtightness, what it is, why it's important, when it's required and how it's carried out.
Construction contract awards hit lowest point of 2025
Plummeting for second consecutive month, intensifying concerns for housing and infrastructure goals.
Understanding Mental Health in the Built Environment 2025
Examining the state of mental health in construction, shedding light on levels of stress, anxiety and depression.
The benefits of engaging with insulation manufacturers
When considering ground floor constructions.
Lighting Industry endorses Blueprint for Electrification
The Lighting Industry Association fully supports the ECA Blueprint as a timely, urgent call to action.
Comments
Brilliant article. We made a document that really simply covers what Ventilation refurbishment actually is and why it can be beneficial as opposed to a replacement. Don't feel any pressure, but have a look if you want a really simple updated definition. Click here
https://www.bvs-ltd.co.uk/2023/06/07/refurbish-or-replace-making-the-right-choice-for-your-ahu-unit/