Refurbishment and Fit Out / UK / 2014 / 02 - Health and Wellbeing /

HEA 04 - Thermal Comfort

Information correct as of 11thApril 2021. 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.  

Assessing industrial spaces – exemptions - KBCN0734

The thermal comfort criteria are not applicable to the operational or storage areas typically found in industrial buildings. The criteria should still be applied to the other parts of the building as appropriate. Operational and storage areas often have function related thermal requirements determined by the needs of the operation or the items being stored. These functional requirements supercede the needs of the occupants.
Technical manual to be updated accordingly in the next re-issue

Building Bulletin 101 2006/2014 - KBCN0786

Within Compliance Note CN4.1 reference is made to the appropriate industry standard for schools being Building Bulletin 101, Ventialtion of school buildings (2014). On the Government website where this bulletin can be found (https://www.gov.uk/government/publications/building-bulletin-101-ventilation-for-school-buildings) it is stated the latest version of the bulletin was published in 2014. However, upon downloading the bulletin, the cover page and version control of the document states Version 1.4- 5th July 2006. We are unaware of any other version of Building Bulletin 101 currently in use. As such, provided the bulletin is downloaded from the official Government website as detailed above, it can be considered the correct version of the bulletin for use within BREEAM. If the thermal modelling specialist recommends an alternative standard, for example TM52, then this would be acceptable provided there is a full justification.

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

The following guidance is intended to clarify the types of area for which user controls are required or would be considered beneficial. Please refer to the specific requirements of the applicable BREEAM Scheme to interpret this guidance appropriately. User controls which allow independent adjustment of heating/cooling systems within the building are required/considered beneficial in the following areas: User controls which allow independent adjustment of heating/cooling systems within the building are not required in the following areas: Please note that zoning is required in all areas of the building where specified in the assessment criteria for this issue.   User controls are required/considered beneficial in spaces which are owned, shared or temporarily owned by individual building occupants. User controls are not required in occasionally visited spaces or spaces where individual occupants are not expected to have control over the thermal conditions. 

Part 2 Assessments & Thermal Zoning - KBCN0460

Some criteria related to thermal zoning and controls may not be applicable to Part 2 assessments. These should however, be addressed as far as possible within the work to the core services and associated infrastructure, given the scope of works. Where compliance with any requirement is not possible, this should be justified by the design team in the evidence for this Issue.
10/02/2017 - This replaces the previous CN which stated, incorrectly, that the criteria relating to thermal zoning do not apply to Part 2 assessments. This approach now aligns with the BREEAM manual and the scoring & reporting tool.

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 environment - KBCN1130

The building design should be evaluated against the projected climate change environment using the DSY weather file for the 50th percentile in: Free Running Buildings Mechanically Ventilated or Mixed Mode Buildings The emissions scenarios are a minimum which can be exceeded should the design team feel that consideration of building occupant risk/sensitivity to overheating is necessary.
Technical manual to be updated at the next re-issue

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.

Reporting PPD and PMV Figures - KBCN0867

The individual carrying out the modelling should be able to provide values for both the PMV and PPD for the building. The PMV and PPD values need to be reported, in the scoring & reporting tool, for data recording purposes. The values to report are the observed range of values for PMV and PPD across all occupied areas across all the hours when these are expected to be occupied (enter the minimum and maximum for each i.e. PMV = 0.2 - 0.5, PPD = 10 - 15%). However, if compliance with the thermal comfort criteria is demonstrated without using a full dynamic thermal analysis software package and via a less complex system, which does not generate the required PMV/PPD metrics, these do not have to be provided.

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 – 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 for Part 1 assessments - KBCN0944

Where a Shell Only (Part 1) assessment is being carried out, but the future servicing strategy is unknown, the thermal comfort credit is still applicable. To assess compliance, the upgraded shell of the building shall be modelled with a typical servicing configuration which meets as a minimum: The thermal modelling credit can be awarded when the notional modelled system achieves the BREEAM thermal comfort criteria. The intent is to ensure that thermal comfort is achievable with the proposed upgraded shell for any future occupiers. The details of the notional system could be passed on to future occupiers or servicing specialists to inform their servicing strategy.

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 11thApril 2021. Please see kb.breeam.com for the latest compliance information.