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HEA 04 - Thermal comfort

Information correct as of 22ndNovember 2019. Please see kb.breeam.com for the latest compliance information.

2020 and 2050 weather files - KBCN0842

The weather files with reference to the 2020s will cover the 30 year climatic period around that decade, i.e. 2010 to 2040, with the 2020s being the middle of the three decades (10's/20's/30's).  Therefore any projects that will be completed before 2025 should use the 2020 weather files for mechanical ventilation and the 2050 weather files for natural ventilation.

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

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

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. 

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.

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 – 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 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.

Weather files applicable internationally - KBCN0732

Prometheus is currently referred to in the technical manual to demonstrate compliance with the 'Adaptability - for a projected climate change scenario' criteria. Since this is not applicable internationally, until an alternative has been formally approved, the following can be used: Climate change world weather file generator Version 1.8  http://www.energy.soton.ac.uk/ccworldweathergen/ Weather files can be found here, or on other national sources. https://www.ashrae.org/resources--publications/bookstore/iwec2 The instructions are included in the first link.
Technical manual to be updated accordingly in next reissue.

Information correct as of 22ndNovember 2019. Please see kb.breeam.com for the latest compliance information.