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Hea 04 Thermal comfort

(all buildings)

Number of credits available	Minimum standards
3	No

Aim

To ensure that appropriate thermal comfort levels are achieved through design, and controls are selected to maintain a thermally comfortable environment for occupants within the building.

Assessment criteria

The following is required to demonstrate compliance:

One credit - Thermal modelling

Thermal modelling (or an analytical measurement or evaluation of the thermal comfort levels of the building) has been carried out using the predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) indices in accordance with ISO 7730:2005 taking full account of seasonal variations.

Local thermal comfort criteria have been used to determine the level of thermal comfort in the building, in particular internal winter and summer temperature ranges will be in line with the recommended comfort criteria within ISO 7730:2005, with no areas falling within the levels defined as representing local dissatisfaction.

Thermal comfort levels in occupied spaces meet the Category B requirements set out in Table A.1 of Annex A of ISO 7730:2005.

For air-conditioned buildings, the PMV and PPD indices based on the above modelling are reported via the BREEAM assessment scoring and reporting tool.

One credit - Adaptability for a projected climate change scenario

Criteria 1 to 4 are achieved.

The thermal modelling demonstrates that the relevant requirements set out in criterion 3 are achieved for a projected climate change environment (see Relevant definitions).

Where thermal comfort criteria are not met for the projected climate change environment, the project team demonstrates how the building has been adapted, or designed to be easily adapted in the future using passive design solutions in order to subsequently meet the requirements under criterion 6

For air-conditioned buildings, the PMV and PPD indices based on the above modelling are reported via the BREEAM assessment scoring and reporting tool.

One credit - Thermal zoning and controls

Criteria 1 to 4 are achieved.

The thermal modelling analysis (undertaken for compliance with criteria 1 to 4 ) has informed the temperature control strategy for the building and its users.

The strategy for proposed heating or cooling systems demonstrates that it has addressed the following:

11.a

Zones within the building and how the building services could efficiently and appropriately heat or cool these areas. For example, consider the different requirements for the central core of a building compared with the external perimeter adjacent to the windows

11.b

The degree of occupant control required for these zones, based on discussions with the end user (or alternatively the building type or use specific design guidance, case studies, feedback) considers:

11.b.i

User knowledge of building services

11.b.ii

Occupancy type, patterns and room functions (and therefore the appropriate level of control required)

11.b.iii

How the user is likely to operate or interact with the systems, e.g. are they likely to open windows, access thermostatic radiator valves (TRVs) on radiators, change air-conditioning settings etc.

11.b.iv

The user expectations (this may differ in the summer and winter) and degree of individual control (i.e. obtaining the balance between occupant preferences, for example some occupants like fresh air and others dislike drafts).

11.c

How the proposed systems will interact with each other (where there is more than one system) and how this may affect the thermal comfort of the building occupants

11.d

The need or otherwise for an accessible building user actuated manual override for any automatic systems.

Checklists and tables

None.

Compliance notes

Ref	Terms	Description
Shell and core (non-residential and residential institutions only)
CN1	Applicable assessment criteria	Thermal modelling: criteria 1 to 4 Shell only: This issue is not applicable. Shell and core: All criteria relevant to the building type and function apply. Adaptability - for projected climate change: criteria 5 to 8 Shell only: These criteria are not applicable. Shell and core: All criteria relevant to the building type and function apply. Thermal zoning and controls: criteria 9 to 11 Both options: These criteria are not applicable. Refer to Appendix D – Shell and core project assessments for a more detailed description of the shell and core assessment options.
CN1.1	Thermal model - thermal modelling. See criteria 1 to 4 .	Shell and core: Where assumptions are required for the purpose of the thermal model, these must be reasonable and represent typical use patterns and loads given the parameters and function of the building. Note that thermal modelling may need to be completed on the basis of a typical notional layout.
CN1.2	Thermal model - adaptability. See criteria 5 to 8 .	Shell and core: Where assumptions are required for the purpose of the thermal model, these must be reasonable and represent typical use patterns and loads given the parameters and function of the building. Note that thermal modelling may need to be completed on the basis of a typical notional layout.
Residential - Partially fitted and fully fitted
CN2	Applicable assessment criteria - Single and multiple dwellings	Both options : All criteria relevant to the building type and function apply. Refer to Appendix E – Applicability of BREEAM New Construction to single and multiple dwellings, partially and fully fitted for a more detailed description of residential assessment options.
General
CN3	Typical occupancy and use patterns	If it is not possible to confirm the number of building occupants using the building, e.g. speculative developments, then the default occupancy rates given in Tra 04 Maximum car parking capacity: Table 36can be used to determine a default number of users. Where the typical use patterns are also unknown, Tra 01 Public transport accessibility: Table 31can be used to determine the typical opening hours of different building types. The design team need to justify or validate the occupancy number and use patterns applied in the thermal model.
CN3.1	Alternative to criterion 3	In some cases it may be more straightforward to demonstrate compliance with the Category B design criteria in Table A.5 in Annex A of ISO 7730:2005. BREEAM considers this an appropriate equivalent to Table A.1; however, the example design criteria included in Table A.5 must be applicable to the building or space type and activity levels for the project. Criterion 4 still requires PMV and PPD to be reported and Annex D of ISO 7730:2005 includes the code of a BASIC program that converts these design parameters into PMV and PPD. By using this program it is possible to obtain the PMV and PPD figures and show direct compliance with Table A.1.
CN3.2	National or local alternative to ISO standard	It is possible to use a national or local equivalent to ISO 7730:2005; however this must be approved by BRE Global. The Approved standards and weightings list can be used to check for previously approved standards or to propose a new national or local standard.
CN3.3	Buildings with less complex heating or cooling systems. See criterion 11 .	For buildings with less complex heating or cooling systems the thermal comfort strategy need only comply with criteria 11.a.and 11.b Compliance can be demonstrated where zoning allows separate occupant control (within the occupied space) of each perimeter area (i.e. within 7m of each external wall) and the central zone (i.e. over 7m from the external walls). For example, adequate TRVs placed in zones around the building perimeter, and the provision of local occupant controls to internal areas, such as fan coil units. Note: The distance requirement for smaller buildings is approximate; however, the assessor must use sound judgment considering fully the aims of this issue, before accepting solutions that do not strictly meet the above criteria. Examples of potentially compliant heating control measures can be found in Technology Guide CTG065 Heating control2CTG065 Technology Guide, Heating control: maximising comfort, minimising energy consumption, The Carbon Trust, 2011.
Building type specific
CN4	Industrial: Industrial unit with no office space	Where an industrial unit contains no office space and only an operational or storage area, this BREEAM issue does not apply.
CN4.1	Education: Occupant controls. See criterion 11 .	In this issue, occupant controls are intended to be for staff use only.

Methodology

None.

Evidence

Criteria	Interim design stage	Final post-construction stage
1–4	The relevant section or clauses of the building specification, or contract or correspondence (e.g. letter, email or meeting minutes) from the design team. Thermal modelling, measurements and evaluation results with confirmation that these are within the required limits. PMV/PPD data from the design team.	Thermal modelling, measurement and evaluation results reflecting any changes to the design and resultant PMV/PPD data with confirmation that these are within the required limits.
6–8	Thermal modelling and evaluation results with confirmation that these are within the required limits. PMV/PPD data from the design team.	Thermal modelling and evaluation results reflecting any changes to the design and resultant PMV/PPD data with confirmation that these are within the required limits.
10–11	Thermal comfort strategy and software results highlighting the points that have been considered and decisions taken accordingly. Confirmation that the modelling software is BREEAM compliant. The relevant section or clauses of the building specification or contract. Design drawings.	As design stage. BREEAM Assessor’s site inspection report and photographic evidence.* *For large buildings it would not be expected that the assessor check every individual occupied space, but a random selection of spaces that confirm compliance.

Criteria

Interim design stage

Final post-construction stage

1–4

The relevant section or clauses of the building specification, or contract or correspondence (e.g. letter, email or meeting minutes) from the design team.

Thermal modelling, measurements and evaluation results with confirmation that these are within the required limits.

PMV/PPD data from the design team.

Thermal modelling, measurement and evaluation results reflecting any changes to the design and resultant PMV/PPD data with confirmation that these are within the required limits.

6–8

Thermal modelling and evaluation results with confirmation that these are within the required limits.

PMV/PPD data from the design team.

Thermal modelling and evaluation results reflecting any changes to the design and resultant PMV/PPD data with confirmation that these are within the required limits.

10–11

Thermal comfort strategy and software results highlighting the points that have been considered and decisions taken accordingly.

Confirmation that the modelling software is BREEAM compliant.

The relevant section or clauses of the building specification or contract.

Design drawings.

As design stage. BREEAM Assessor’s site inspection report and photographic evidence.*

*For large buildings it would not be expected that the assessor check every individual occupied space, but a random selection of spaces that confirm compliance.

Relevant definitions

Occupied space

Refer to Hea 01 Visual comfort, however for the purpose of BREEAM issue Hea 04 the definition excludes the following:

Atria or concourses
Entrance halls or reception areas
Ancillary space, e.g. circulation areas, storerooms and plant rooms.

Passive design

Passive design uses layout, fabric and form to reduce or remove mechanical cooling, heating, ventilation and lighting demand. Examples of passive design include optimising spatial planning and orientation to control solar gains and maximise daylighting, manipulating the building form and fabric to facilitate natural ventilation strategies and making effective use of thermal mass to help reduce peak internal temperatures.

Predicted mean vote (PMV)

The PMV is an index that predicts the mean votes of a large group of persons on the seven-point thermal sensation scale based on the heat balance of the human body. Thermal balance is obtained when the internal heat production in the body is equal to the loss of heat to the environment. See Other information for the seven-point thermal sensation scale.

Predicted percentage dissatisfied (PPD)

The PPD is an index that establishes a quantitative prediction of the percentage of thermally dissatisfied people who feel too cool or too warm. For the purposes of ISO 7730, thermally dissatisfied people are those who will feel hot, warm, cool or cold. See the seven-point thermal sensation scale in Other information.

Projected climate change environment

Dynamic thermal simulation software packages currently provide the facility for building designs to be assessed under external climatic conditions specific to geographic location. Industry standard weather data should be sought from an appropriate local or national best practice standard in the form of Test Reference Years (TRYs) and Design Summer Years (DSYs).

The weather data enables thermal analysis of building designs under current climatic conditions, yet no account is normally taken of the projected variations in weather data that will occur during the building's life cycle as a result of climate change. To demonstrate compliance, weather data should be used based upon a projected climate change scenario. The following probabilistic DSY weather data files should be used to establish the projected climate change environment against which the design is evaluated:

Naturally Ventilated Buildings

Time period: 50 years after construction is complete
Emissions scenario: Medium (A1B)

Mechanically Ventilated or Mixed Mode Buildings

Time period: 15 years after construction is complete
Emissions scenario: Medium (A1B)

The above weather files represent the minimum requirements to perform thermal modelling under a climate change scenario and subsequently demonstrate compliance. Where design teams feel that added consideration of building occupant risk or sensitivity to overheating is necessary, weather files can be used that exceed the minimum requirements outlined above. The time periods indicated above have been selected to represent the building services life cycle likely to be present in each building services strategy type. A shorter time period is chosen for mechanically ventilated or mixed-mode building types due to consideration of mechanical servicing equipment life span (before major upgrade or replacement is required), and to avoid over-specification of plant which could lead to inefficient operation. This should be sought from a recognised local or national best practice standard or organisation. Verification should be sought from BRE Global prior to using any such standards in an assessment.

Separate occupant control

Responsive heating or cooling controls for a particular area or zone of the building that can be accessed and operated by the individuals occupying that area or zone. Such controls will be located within, or within the vicinity of, the zone or area they control.

Thermal comfort

In EN ISO 7730:2005: Ergonomics of the thermal environment. Analytical determination and interpretation of thermal comfort, 'thermal comfort' is defined using the calculation of PMV and PPD indices and local thermal comfort criteria and is 'that condition of mind which expresses satisfaction with the thermal environment.' The term 'thermal comfort' describes a person's psychological state of mind and is usually referred to in terms of whether someone is feeling too hot or too cold. Thermal comfort is difficult to define because it needs to account for a range of environmental and personal factors in order to establish what makes people feel comfortable. The purpose of this issue is to encourage appropriate and robust consideration of thermal comfort issues and specification of appropriate occupant controls to ensure both maximum flexibility of the space and thermal comfort for the majority of building occupants.

Thermal dynamic analysis

Thermal comfort analysis tools can be subdivided into a number of methods of increasing complexity. The most complex of these and the one that provides greatest confidence in results, is the full dynamic model. This type of model enables annual heating or cooling loads, overheating risks and control strategies to be assessed.

Other information

Projected climate change weather data

The Intergovernmental Panel on Climate Change (IPCCIntergovernmental Panel on Climate Change) 5th Assessment Report outlines future climate change scenarios that can be used to project a range of alternative probabilistic weather data. These weather data should be used to evaluate the impact of varying climate change scenarios for the country to influence building design performance for the building throughout its life cycle. Projected climate change weather data should be sourced in TRYs and DSYs.

While not internationally applicable, reference can be made to the UK PROMETHEUS project at Exeter University that produced a number of future weather files specific to different locations across the UK, created using the UK Climate Projection 2009 (UKCP09) weather generator. Weather files produced under the PROMETHEUS project are available at the following location:

emps.exeter.ac.uk/engineering/research/cee/research/prometheus/downloads/