HEA 04 - Thermal comfort - BREEAM Knowledge Base

Acceptable deviations – ISO 7730:2005 category B - KBCN1714

Acceptable deviations from the ISO 7730:2005 category B criteria thermal modelling criteria can be made in accordance with CEN 16798-2:2019 Annex E. Up to a 6 % deviation based on yearly occupied hours can be accepted when demonstrating compliance.

Adaptability for a projected climate change scenario – Winter conditions - KBCN1715

Where future climate change scenario projections in winter indicates a higher temperature and, therefore, more thermally comfortable climate compared to the current winter temperatures, it can be assumed that the winter conditions within the climate change scenario are met based on the thermal modelling of current winter conditions. Justification must be provided for each project confirming that the future winter conditions will be met with the current heating system. In a warming climate the heating system needs to be sized for the beginning of its lifespan, whereas the cooling systems need to be sized for the end of their life span (Ref: CIBSE TM55: 2014)

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%.

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.

Assessing thermal comfort – Residential buildings - KBCN1408

CIBSE TM59 can be used to demonstrate compliance with the thermal comfort requirements for residential and multi-residential buildings (long-term stay), instead of ISO 7730:2005. This is to recognise the most up to date methodology relating to the assessment of homes.

26 Jan 2025 - Updated to apply to multi-residential buildings (long-term stay) and scheme applicability extended to account for this.

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.

Natural ventilation – use of CIBSE TM52 - KBCN0935

For a naturally ventilated building, it is acceptable for the thermal comfort limits and calculation methodology in CIBSE TM52: The Limits of Thermal Comfort: Avoiding Overheating in European Buildings to be used in place of ISO 7730:2005. BREEAM recognises that adaptive comfort models can provide more appropriate thermal comfort limits for naturally ventilated buildings.

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.

Owned spaces: small rooms for a few people. For instance, cellular offices, owned spaces in residential assets.
Temporarily owned spaces: where occupants expect to operate the environmental controls while they are there. For instance, meeting rooms and hotel bedrooms.
Shared spaces. For instance, multi-occupied areas such as open-plan offices or workshops.

User controls not required Spaces where users are not expected to have independent control over their environment.

Managed spaces: where environmental control is expected to be centrally managed. For instance, atria, circulation areas, concourses, entrance halls, function halls, restaurants, libraries, and shops.
Occasionally visited spaces. For instance, storerooms, bookstacks in libraries, aisles of warehouses, toilets.

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.

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:

Across all occupied areas and,
Across all expected occupied hours.

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:

PMV ranges from -0.3 to +0.2. Enter '-0.3 to +0.2' into the relevant field.
PPD ranges from 3% to 10%. Enter '3% to 10%' into the relevant field.

[/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 – full dynamic thermal analysis - KBCN1250

The software used to carry out the thermal modelling simulation at the detailed design stage needs to provide full dynamic analysis. For smaller and more basic building designs with less complex heating/cooling systems, an alternative less complex means of analysis may be appropriate. Further guidance on thermal modelling can be found in CIBSE AM11 Building energy and environmental modelling.

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.

Weather files – 50th percentile - KBCN0117

For the thermal simulation of climate change environments, where this not specified in the manuals, the 50th percentile weather file is used in all cases. This applies also to the use of any alternative weather files or formats which are not listed in the manual. See KBCN1182.

18-Dec-2024 - Title updated for clarity. Scheme applicability updated. Link to KBCN1182 added.

Weather files – alternative format or location - KBCN1182

Alternative format Newer weather files, or alternative weather file formats not listed in the manuals can be used instead of those referenced in the manual, if they achieve the aim of the credit. These alternative files must be based on climate projections with equal or higher temperatures than those specified in the relevant criteria, setting an equally or more robust standard for overheating. The alternative weather files must include same variables as the specified weather files for each hour of the year e.g.: - Dry bulb & wet bulb temperature, - Wind speed & direction, - Solar altitude & azimuth, - Cloud cover etc. The assessor or design team must verify this and ensure that meeting the BREEAM criteria does not become easier by using the alternative weather file. Alternative location Where the weather file for the nearest location for the project is not representative of the actual location’s climatic conditions, the project team can use the weather file from another nearby location which is more representative. This can take account of the climatic influences of altitude, prevailing wind, proximity to climate-moderating features, or heat island effect.

18-Dec-2024 - Merged with KBCN1013. Scheme applicability updated.

Weather files – files applicable internationally - KBCN0732

The technical manual refers to Prometheus, which is not applicable internationally for the projected climate change scenario criteria. Until an alternative has been formally approved, the following can be used: Climate Change World Weather File Generator ASHRAE weather data files

18-Dec-2024 - Title updated. Link updated.

[Withdrawn] – Weather file location - KBCN1013

Content merged with KBCN1182. 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.

18-Dec-2024 - Content merged with KBCN1182.

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HEA 04 - Thermal comfort