CIBSE launches free four-part London event series on who owns the building performance gap

The Chartered Institution of Building Services Engineers (CIBSE) has launched a free four-session event series, Who owns the performance gap?, at its London headquarters to examine why buildings perform differently in operation from their design intent.

The sessions run on 5, 12 and 18 November and 1 December 2026, each from 13:00 to 17:00, at CIBSE HQ, 91–94 Saffron Hill, London EC1N 8QP, according to the institution's announcement published on 7 October.

CIBSE said the series would bring together industry professionals to look at the causes of the gap between design intent and measured performance, and to explore practical ways to reduce it. It said the central question for the series was who is responsible for ensuring that buildings perform as intended.

The institution said closing the gap "requires collaboration and accountability across the whole project team", from early-stage design and modelling through construction, commissioning, operation and post-occupancy evaluation.

The four sessions

The first session, on 5 November, covers equipment sizing, controls and metering. According to CIBSE's event listing, speakers will look at how oversizing or undersizing plant affects the performance gap and how smarter controls, metering and recommissioning can help reduce it.

Session two, on 12 November, turns to energy performance and heat network design. CIBSE said it would focus on the design and delivery of heat networks and retrofit projects that perform as intended, drawing on comparisons between design expectations and measured building performance.

The third session, on 18 November, deals with modelling and software at design stage. CIBSE said speakers would examine predictive modelling, weather data, ventilation, controls and performance assessment.

The series closes on 1 December with a session on post-occupancy evaluation and what CIBSE calls a vision for the future. It will include a keynote presentation, case studies and industry reflections on practical ways to improve accountability and close the gap between design intent and operational reality.

All four events are free to attend in person, CIBSE said.

Background

CIBSE has published guidance on the performance gap since 2013. Its technical memorandum TM54, Evaluating operational energy performance of buildings at the design stage, was published in October 2013 and describes the difference between expected and realised energy performance as the performance gap.

TM54 identifies one cause as the fact that compliance energy calculations do not account for all of a building's energy uses, omitting lifts and escalators, catering facilities and server rooms.

CIBSE revised TM54 in February 2022 so that it covers steady-state modelling as well as dynamic simulation, with guidance on choosing the most appropriate modelling approach and level of detail for each project.

Julie Godefroy, CIBSE Head of Sustainability, said at the time: "CIBSE Technical memoranda offer guidance on recommended practices and the update to TM54 reflects recent developments in building performance evaluation throughout the project cycle."

More recently, CIBSE held a conference, Building Performance Reimagined – What's Next?, at the Royal Society in London on 26 November 2025. It also ran a one-day event under the same Who owns the performance gap? title on Thursday 4 June, which its Eventbrite listing shows has now ended. CIBSE describes the four-session series as new.

Booking for the series is open through CIBSE's events pages, with the first session on equipment sizing, controls and metering on 5 November 2026.