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

Hea 04 - Thermal comfort

Information correct as of 11thApril 2021. Please see kb.breeam.com for the latest compliance information.

00 Blank note - KBCN0997

Please note: If there are no other compliance notes below this one it simply means that none exist yet for this issue.

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.

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 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 – 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.
Information correct as of 11thApril 2021. Please see kb.breeam.com for the latest compliance information.