New Construction / UK / 2014 / 02-Health and Wellbeing /

Hea 04 – Thermal comfort

Information correct as of 24thMay 2024. Please see kb.breeam.com for the latest compliance information.

2030s weather files - KBCN000006

The Exeter University Prometheus project contains future weather files which cover the 2030s. These can be found here: https://emps.exeter.ac.uk/engineering/research/cee/research/prometheus/downloads/
13 09 2017 Hyperlink to Prometheus project updated. Applicability to BREEAM International schemes removed - (see  KBCN0732)

Air-conditioned spaces - KBCN00035

Air-conditioned spaces are assessed to ensure appropriate thermal comfort levels are achieved. Cooling capacity should be sufficient to comply with the requirements of CIBSE Guide A, however providing sufficient space to install additional capacity to meet the requirements at a later date in line with projected climate change scenarios is also acceptable. In addition, if it can be demonstrated that the air-conditioning system can achieve the thermal comfort criteria in accordance with CIBSE Guide A, Table 1.5, thermal modelling does not need to be carried out. The “time out of range” (TOR) metric should be reported as 0%.  

Alternative weather files - KBCN1182

Different or newer weather files can be used instead of those referenced in the manual, as long as they achieve the aim of the credit. Weather files based on climate projections with higher temperatures than those specified in the relevant criteria, set a more robust standard for overheating and so they are acceptable. The alternative weather files need to include same variables as the specified weather files e.g. dry bulb & wet bulb temperature, wind speed & direction, solar altitude & azimuth, cloud cover etc. for each hour of the year. It is the role of the assessor or design team to verify this and ensure that meeting the BREEAM criteria does not become easier by using the alternative weather file.

Approach to thermal model when using BMS - KBCN0169

Where there are smart systems such as BMS in place, modelling must consider normal operating conditions, with the heating and cooling system in operation regardless of the control strategy. In order for the design team to size the heating/cooling plant, they will carry out modelling to calculate the heat/cold loss throughout the year. Results of these calculations must be submitted, with the heating/cooling plant specification which would demonstrate that the building has been designed to ensure internal winter/summer temperatures will not drop below an acceptable level, and that in effect the winter TOR is zero.
14 Apr 2023 Applicability to UK NC2018 and UK/Int V6 confirmed

Assessing industrial spaces – exemptions - KBCN0734

The thermal comfort criteria do not apply to the operational or storage areas typically found in industrial assets or other similar asset types. The criteria is still be applied to the other parts of the asset as appropriate. Operational and storage areas often have function-related thermal requirements determined by operational or storage needs. These functional requirements override the needs of any occupants.
17-Jan-2024 - Scheme applicability updated.
03-Nov-2020 - Issue 2.0 of UK RFO technical manual updated with new CN detailing the above.

Building Bulletin 101 - KBCN0786

Within Compliance Note CN4.1, reference is made to the appropriate industry standard for schools being Building Bulletin 101: Ventilation of school buildings (2014). This has been updated to BB101 2018, so either the current version or the specified 2014 standard may be used to demonstrate compliance. If the thermal modelling specialist recommends an alternative standard, for example TM52, then this would be acceptable provided there is a full justification.
11/08/2021 Updated to recognise the current version of the standard

Definition of concourse - KBCN0386

A concourse is an open area within or in front of a public building which is used primarily for circulation, short term waiting, or incidental interaction, analogous to the concourse of a train station. It should not be considered occupied space.  

Occupant control – BMS and degree of control - KBCN0175

A Building Management System controlled set point with local override controls limited to a set range would satisfy the occupant control requirement so long as the temperature range available to building users is confirmed as appropriate for the building type and user profile.

Occupant control – spaces requiring user controls - KBCN0170

This guidance is intended to clarify the types of area for which user controls are required or would be considered beneficial. Zoning is required in all areas of the asset where specified in the assessment criteria. Please refer to the specific requirements of the applicable BREEAM standard to interpret this guidance appropriately. User controls required Spaces where users are expected to have independent control over their environment. User controls not required Spaces where users are not expected to have independent control over their environment.
14-Dec-2022 - KBCN applicability updated to include BIU. Wording clarified, and amended for compatibility with BIU criteria.

PMV and PPD reporting for mixed mode ventilation buildings - KBCN0632

When assessing buildings where both naturally ventilated and air conditioned spaces are included, reporting the PMV and PPD indices is required.

Projected climate change weather file - KBCN0117

Although other scenarios are available, for the thermal simulation of climate change environments, the 50th percentile weather file should be used for consistency with other assessments.
03.11.2020 Amendment made to include this information in issue 2.0 of UK RFO 2014 technical manual, but this KBCN is applicable to all issues of the technical manual.

Reporting PPD and PMV Figures - KBCN0867

The PMV (Predicted Mean Vote) and PPD (Predicted Percentage Dissatisfied) values need to be entered into the scoring & reporting tool for data recording purposes. The thermal modelling specialist should be able to provide values for both the PMV and PPD for the asset. The values to report are the observed range of values for PMV and PPD: If the software or calculation method used does not generate these PMV / PPD metrics, they do not have to be provided. [accordion] [accordion_block title="Example"] An asset has the following thermal comfort ranges across its occupied spaces: [/accordion_block] [/accordion]
15.09.22 Wording and example clarified.

Thermal comfort – Changing rooms - KBCN1133

Whilst thermal comfort in changing rooms may be considered as significant, such spaces are, generally, outside the scope of this Issue, as they would not fall within the definition of an 'occupied space'.
17/06/2019 - This supersedes the advice previously provided in this KBCN, which was published in error on 13/06/2018

Thermal modelling – mechanical ventilation with no heating or cooling - KBCN1579

Where the building services include mechanical ventilation with no heating or cooling element this is considered "free-running". These buildings do not need to follow the air-conditioned building criteria. If the building services do not include any mechanical cooling, then the risk of overheating is down to the use of the building fabric to afford attenuation of the diurnal swings / solar gains. Therefore the adaptive approach to thermal comfort from CIBSE AM10 is the correct approach to define and assess summer overheating /thermal comfort against. Following the Adaptive model is seen as allowing a lot of tolerance for the required indoor conditions. A full DTM assessment will be required to show the predicted summer internal conditions.

Thermal modelling – naturally ventilated buildings with heating for the winter months - KBCN1345

Where naturally ventilated occupied spaces are heated in the winter/heating season, as an alternative to demonstrating compliance with the winter operative temperature ranges in CIBSE Guide A or other appropriate industry standard, such occupied spaces can demonstrate compliance through meeting the Category B requirements for PPD, PMV and local discomfort set out in Table A.1 of Annex A of ISO 7730:2005. Where this alternative compliance route is used, when these naturally ventilated occupied spaces are in ‘free-running mode’ (i.e. outside of the winter/heating season), it is not possible to use the ISO 7730:2005 method and therefore these spaces must demonstrate compliance with the requirements to limit the risk overheating in accordance with CIBSE TM52.

Thermal modelling for large scale projects - KBCN1171

In cases where the scale of the project makes it unfeasible to provide thermal modelling for every space, it is acceptable to demonstrate compliance with a representative sample of floors or rooms, ensuring any worst case scenarios are included.

Thermal modelling – buildings with mixed-mode ventilation - KBCN1346

Where a building has some occupied spaces that are naturally ventilated and some occupied spaces that are air-conditioned, the thermal modelling must demonstrate that the naturally ventilated spaces meet the criteria for naturally ventilated buildings and that the air-conditioned spaces meet the criteria for air-conditioned buildings.

Weather File Location - KBCN1013

In accordance with the guidance provided in CIBSE AM11, in instances where the weather file for the nearest location does not represent the most appropriate climatic conditions for the actual location, it is permissible to use the weather file from another, nearby location, which more closely matches the climate at the actual location. This can take account of the climatic influences of height above sea level, a coastal location or other local, climate-moderating features such as mountains, woodland, lakes, prevailing wind direction or urban heat island effect.
Information correct as of 24thMay 2024. Please see kb.breeam.com for the latest compliance information.