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.

Manual errata – Passive design – Industrial assets with no occupied spaces - KBCN1492

This KBCN relates to industrial assessment targeting the 'Passive Design' credit in Ene 04. Specific note 2.1 in Ene 04 states:

Industrial

Hea 04 Thermal comfort: Criterion 1 is not applicable to industrial units that only contain an operational or storage area and are without office space or other occupied spaces. However, to achieve the Ene 04 Passive design analysis credit, compliance with criteria 1, 2 and 3.b.ii in Hea 04 Thermal comfort must be demonstrated.

This is incorrect. It should say: Hea 04 Thermal comfort: This issue is not applicable to industrial units that only contain an operational or storage area and are without office space or other occupied spaces. If the industrial asset is Shell Only without any occupied spaces, this specific note 2.1 overrides specific note 1.2 regarding thermal modelling requirements for Shell Only assets. This will be clarified and corrected in the next re-issue of the manual.

Manual errata – Passive design – Shell only assets - KBCN1493

This KBCN relates to Shell Only assets targeting the ‘Passive Design’ credit in Ene 04. Specific note 1.2 in Ene 04 states:

Hea 04 Thermal comfort: Criterion 1 is not applicable to Shell only assessments. However, to achieve the Ene 04 Passive design analysis credit, compliance with criteria 1, 2 and 3.b.ii in Hea 04 Thermal comfort must be demonstrated.

This is incorrect. It should say: Ene 04 Low Carbon Design: Criterion 1 is not applicable to Shell only assessments. However, to achieve the Ene 04 Passive design analysis credit, compliance with criteria 1, 2 and 3.b.ii in Hea 04 Thermal comfort must be demonstrated. This will be corrected in the next re-issue of the manual.

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 – 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 files – 2020s, 2030s and 2050s - KBCN0842

Timescale The weather files for each decade cover a 30-year climatic period around that decade. For example, 2020s weather files cover the period 2010 to 2040. 2020s are in the middle of the three decades (10s / 20s / 30s). NC - 2020s and 2050s New Construction projects assessed under the relevant standards should continue to use the 2020 weather files for mechanical ventilation, and the 2050 weather files for natural ventilation. CIBSE weather files are available here: CIBSE Weather Data RFO - 2030s and beyond When published, the original intent for RFO projects was for future thermal comfort to be based on projected climate change 15 years after completion.

For projects completed between 2015 and 2025, the 2030s data may still be used. This can be found here: Prometheus weather data.
For projects completing after 2025, use CIBSE weather data covering the 2040s (included within the 2050s data): CIBSE Weather Data.

08-Jan-2024 - Added clarification on RFO 2030s data.
18-Dec-2024 - Merged with KBCN000006. Prometheus link updated. Title updated.
04-Jul-2024 - Clarified that 2020 and 2050 weather files are still valid for the applicable standards and guidance applied to all relevant UK standards. Applicability to international standards removed and link to CIBSE weather data added.

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.

New Construction / UK / 2018 / 02 Health and Wellbeing /

Hea 04 - Thermal comfort