The Heatwave Plan for England acts as a good practice guide protecting the public from overheating hazards. Within the Heatwave plan it is advised that cool rooms maintaining temperatures below 26C should be provided in the case of hot weather in hospitals, care/nursing homes and other residential environments occupied by vulnerable individuals (NHS England, 2015).
The London Plan requires the risk of overheating to be demonstrated during planning applications of major developments. More specifically, London Plan Policy 5.9 sets out an overheating and cooling hierarchy for developments and buildings (GLA, 2016).
Overheating Assessment Methods and Standards
In terms of Thermal Comfort & Overheating assessment methods, these include simple internal / external temperature models, predictive models like in the case of the Fanger’s PMV and adaptive comfort models.
The two methods most frequently used in the UK for the assessment of overheating at homes include the usage of the steady-state conditions SAP compliance tool (Standard Assessment Procedure) and the usage of dynamic thermal modelling tools following CIBSE Guidance on overheating.
SAP is a compliance tool mainly focusing on the energy rating of homes. Appendix P of SAP, which assesses the internal temperatures of homes in summer.
Dynamic thermal modelling follows a more sophisticated approach allowing the assessors to use additional variables and specify important parameters that best describe each building’s particular case.
Design standards often used for the prediction of overheating include guidance provided by ASHRAE55, BS EN 15251:2007 (for free running buildings) and CIBSE including CIBSE Guide A 2006 & 2017, CIBSE TM52:2013, and CIBSE TM59:2017.
The most recent CIBSE TM59:2017 standardises the assessment method for dynamic thermal modelling of overheating at homes.
Design, Construction and Handover Guidelines
Identifying the right design strategy strongly links to the experience and expertise of the design and building engineers involved in the project. Current minimum Building Regulation ventilation requirements may not suffice and will not cover overheating.
Concerns around overheating may lead to additional policies and regulations being introduced by government in the future, if industry solutions fail to address the problem.
In terms of modelling it is strongly advised that appropriate thermal models, with correct input data, are developed and reviewed at an early stage of the design strategy and are being kept up to date as the project progresses.
Changes during the construction stage, due to value engineering, procurement or simply on-site ‘quick solutions’ need to be carefully documented and communicated back to the design team.
The Housing Supplementary Planning Guidance, published in March 2016, discusses property types that might be more susceptible to overheating or be affected by noise, as is single aspect flats.
As mentioned in the report dual aspect dwellings are favoured due to the ability to cross-ventilate while for dwellings that cannot have openable windows due to poor air quality or noise restrictions, careful consideration needs to be given to the location of air intake units and any increased potential for overheating in the summer due to the reduced opportunities for natural ventilation.
In terms of building services and HVAC systems, these need to be installed, tested and commissioned properly by certified engineers. BSRIA’s technical library offers a wealth of information on a variety of systems testing and commissioning requirements.