NHS Scotland, NSS Health Facilities Scotland - Energy & Thermal Comfort Modelling


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IES Consulting worked in collaboration with Mabbett & Associates to examine the performance gap and thermal comfort issues experienced in new healthcare buildings in Scotland and proposed a new approach to future NHS developments.

Key Facts

  • Newly built healthcare facilities falling short of design predictions
  • Improved data required for energy & thermal comfort modelling at all stages of building development
  • Proven methods to more accurately predict issues early on
  • New approach proposed to future NHS developments

A project undertaken by Health Facilities Scotland (HFS) - part of NHS National Services Scotland - IES Consulting and Mabbett & Associates has demonstrated the importance of implementing accurate data for energy & thermal comfort modelling from the early stages, and throughout, the design process.

HFS commissioned the study after realising that a number of new NHS healthcare buildings were falling short of their energy and comfort design predictions once in operation. In particular, they wanted to understand and address issues concerning space overheating causing uncomfortable conditions for occupants and elevated cold water temperatures leading to increased water safety risks. These issues were apparent despite the building designs and design stage modelling demonstrating compliance with local government building regulations.

IES Consulting first created baseline models, representative of a typical health centre and hospital ward, using the UK government sourced National Calculation Method (NCM) data. Currently, UK building compliance is tested against this data, but it is also widely used for design and compliance calculations in the absence of intended operational data. However, unfortunately, it only takes into consideration heat gains attributed to occupied spaces including loads for people, lighting and equipment, meaning important gains from hot pipework and electrical cables in adjacent voids can be omitted from the calculations entirely.

The consultants then modelled the same buildings using "improved" data, gathered and provided by Mabbett & Associates from representative existing buildings, to create Corrected Base Case (CBC) models that more accurately reflect the health centre and hospital buildings in operation.

The discrepancy between the NCM and CBC data was significant. In the case of hospital bedrooms, the real world energy consumption, and associated heat gain, within the space was up to six times higher than the NCM data assumed. The CBC simulations therefore demonstrated increased risk of overheating, with more than 1,000 hours of predicted overheating per year compared to 0 hours when using the NCM data. Inconsistency between the profiles used for lighting energy use and occupancy schedules, and insufficient consideration of the impact of recent changes in Scottish building regulations at design stage (including increased insulation and air tightness standards) were also highlighted as contributing to the performance gap experienced in new buildings.

The analysis highlighted that many operational issues could have been predicted, thus better informing the client and the design at key stages in order for them to be rectified. To prevent similar issues arising in future NHS developments, IES Consulting and Mabbett & Associates presented a number of recommendations to HFS in their final report, including:

  • Superior design modelling procedures to be integrated across the project team.
  • More realistic input data/identification of measures to be considered at each stage.
  • A standardised approach to identifying the analysis needed alongside the required results format to enable direct comparison across analyses.
  • Auditing of analysis models at key milestone stages.
  • Customised project mentoring/training NHS clients in the analysis of relevant design aspects
  • Design and Knowledge databases to assist with benchmarking and provide operational templates across different building types.
  • Potential revision of healthcare facility guidance.
  • Feedback for future design decisions from operational energy and associated data from newly constructed buildings.
  • Modelling approach to be applied to in-use buildings to predict the impact of planned changes in operations e.g. opening longer hours, upon energy use, thermal comfort, etc.

“IES and Mabbett & Associates have worked closely with NHS Health Facilities Scotland to develop this report on recent performance gaps and future modelling in two exemplar inpatient and outpatient new build projects. This innovative report provides tools that should substantively improve future briefing of NHS Scotland new build projects, and thereby enable better, more sustainable facilities and ultimately improved service outcomes for users.”  
- Susan Grant, Principal Architect, NHS Health Facilities Scotland

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