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Hea 01 Daylighting

Number of credits available Minimum standards

2

No

Aim

To improve the quality of life in homes through the provision of good daylighting and to reduce the need for energy to light the home.

Assessment criteria

Up to two credits may be awarded for this issue as follows:

First credit—maintaining good daylighting

  1. For existing dwellings and change of use projects (e.g. conversions):
    1. The refurbishment results in a neutral impact on the dwellings daylighting levels in the kitchen, living room, dining room and study with “no” answered for all questions in Appendix A: Hea 01 , parts 1 and 2 (for existing dwellings) or parts 3 and 4 (for change of use e.g. conversions).
  1. Where the property is being extended:
    1. new spaces achieve minimum daylighting levels See Criteria CN1
    2. the extension does not significantly reduce daylighting levels in the kitchen, living room, dining room or study of neighbouring properties. See CN4

Second credit—minimum daylighting

  1. The dwelling achieves minimum daylighting levels in the kitchen, living room, dining room and study See Criteria CN1

Assessment Procedure

Criteria Description

Criterion

First Credit

1

  1. Obtain a completed copy of Appendix A: Hea 01
  2. Refer to definitions for further guidance on Checklist A-7; Daylight Factor

2

  1. Obtain daylighting calculations for any new kitchen, living room, dining room or study in the extension referring to CN2 and completing Hea 01 daylighting calculator
  2. Refer to CN1
  3. Confirm the daylighting calculations show the minimum daylighting levels have been met
  4. Obtain angular calculations on the site plan and elevation between the extension and the window of the neighbouring property. Refer to CN4

Criterion

Second Credit

3

  1. Obtain daylighting calculations for the kitchen, living room, dining room and study referring to CN2 and completing Hea 01 daylighting calculator
  2. Refer to CN1
  3. Confirm the daylighting calculations show the minimum daylighting levels have been met for the kitchen, living room, dining room and study

Compliance notes

Compliance notes

CN1

Minimum daylighting levels

First Credit—New spaces created from an extension

  1. Where any new spaces created meet a minimum average daylight factor including:
  1. Where kitchens achieve a minimum daylight factor of at least 2%
  2. Where living rooms, dining rooms and studies achieve a minimum average daylight factor of at least 1.5%
  3. Where 80% of the working plane in each new space including kitchens, living rooms, dining rooms and studies, receive direct light from the sky.
  1. Where the dwelling is extended (including loft conversions), 80% of the working plane in each new spaces created including a kitchen, living room, dining room and study, receives direct light from the sky
  2. There is a neutral impact on existing spaces as a result of refurbishment in accordance with criterion 1

Second Credit—Existing dwellings and dwellings created from a change of use (i.e. conversions):

One credit is awarded where the dwelling achieves the following daylighting criteria:

  1. Where kitchens achieve a minimum daylight factor of at least 2%
  2. Where living rooms, dining rooms and studies achieve a minimum average daylight factor of at least 1.5%
  3. Where 80% of the working plane in the kitchen, living room, dining room and study, receives direct light from the sky

CN2

Daylighting Calculation procedures

In all cases it is recommended that calculations are supplied by a daylighting expert. Where this is not possible, the BREEAM Domestic Refurbishment Assessor should carry out a reasonableness check of any calculations provided, cross referencing against building dimensions used in SAP calculations or carry out the calculations themselves using the Hea 01 calculator. For large scale projects, checks should be performed on one room per dwelling, in 10% of dwellings up to a maximum of 10 dwellings per site.

Calculation procedures for Daylight Factor (DF) and typical values are detailed in Littlefair (2011):

  • The DF formula can be used to model daylighting conditions in any simple rectangular room with a continuous external obstruction or none. For L-shaped rooms, it is acceptable to divide the room into two sections and calculate the DF for each section based only on the windows present in that section. The DF of both sections can then be averaged to give a final result.
  • Where external obstructions are of complex geometry and cannot be approximated by a continuous object, it is advisable to use the methodology in Littlefair (1998) (4). Individual trees can be ignored.
  • More complex room geometries can be modelled using computer simulation software, physical scale modelling or advanced manual calculations. BREEAM does not specify ‘compliant’ computer software. The individual carrying out the daylighting calculations must select the most appropriate.
  • Where there are two types of room which form part of the same large space, for example, an open-plan kitchen-dining room, calculate as one room as there is no solid partition present to block the distribution of the daylight. Credits will then be awarded on the basis of the DF of the whole space. For example, if the space is used as a kitchen, a living room and a dining room, the same DF will be used when assessing all these areas against the levels set out above.
  • When two or more windows in a room face different obstructions (e.g. vertical windows and roof lights) or differ in transmittance, the DF should be found separately for each window, and the results summed.
  • Plotting of the no-sky line or estimating the percentage of the working plane that receives direct light from the sky can be done using the Hea01 Daylighting calculator. It must be understood that this methodology will underestimate the actual percentage of the working plane that receives direct light from the sky because obstructions are unlikely to be infinite. Where obstructions are not horizontal, parallel to the window or considered infinite, refer to Littlefair (1998) (4) for a more accurate methodology.
  • Seeking expert advice is recommended to carry out daylighting calculations as mentioned above. However, assessors are not prohibited from performing calculations. It is up to the assessorl and project team to judge whether the assessor has sufficient expertise to do this. Further guidance on how to complete calculations can be found in BS 8206–2:2008, Lighting for buildings—Part 2: Code of practice for daylighting (2).

CN3

Sun pipes

As a general rule, sun pipes should be treated as roof lights, i.e. if there are no obstructions use a u of 180°. There are a wide range of light pipes on the market with different reflective linings and some include lenses/mirrors etc. If no transmission factor is stated, use T = 0.5 for a 1 m length pipe and T = 0.25 for a 2 m length pipe

CN4 Impacts on Neighbouring Properties

To assess the impact on a neighbouring property, angular measurements would need to done on the site plan and elevation plan between the extension and the adjacent property. These are set out in chapter 2.2 of BRE Report 'Site layout planning for daylight and sunlight: a guide to good practice' (BR 209). If the extension is adjacent to the neighbouring property it will significantly reduce daylighting levels in the kitchen, living room, dining room or study of neighbouring properties if:

  • The Centre of neighbour’s window is within both 45 degree angles of the extension. (The 45oapproach) AND
  • The vertical sky component (VSC) is less than 27% or less than 0.8 times its value without the extension

If the extension is opposite the neighbouring property it will significantly reduce daylighting levels in the kitchen, living room, dining room or study of neighbouring properties if the vertical sky component (VSC) is less than 27% or less that 0.8 times its value without the extension. Angular calculations would need to be drawn on the site and elevation plan of the extension to show compliance with the above.

CN5 Default values for dwellings with no obstructions An angle of visible sky of 65 degrees is the default for where there are no obstructions. Calculations would still need to be done to take into account the size of the window, area weighted reflectance of room surfaces, total area of room surfaces, the correction factor for dirt and glass transmission factor. The reason for this is that the dwelling may have small windows compared to the room size, or potentially just a roof light which could have a high correction factor for dirt.

Schedule of Evidence Required

Ref

Design Stage

Post-refurbishment Stage

All Credits

Req 1, 2 & 3

  1. A completed signed and dated copy of
    Appendix A: Hea 01 , parts 1 and 2, or parts 3 and 4 as relevant.
    AND
    Where relevant, calculations to demonstrate:
  2. Average daylight factor using the the Hea01 calculator.
    AND
  3. Position of the no-sky line and percentage of area of the working plane that receives direct light from the sky.
  1. Where Post Refurbishment assessment only or where documentary evidence differs from that provided at the Design Stage, then provide detailed documentary evidence, as listed for Design Stage, representing the dwelling/s as refurbished.
    OR
    Written confirmation from the developer that the dwelling/s have been refurbished in accordance with the detailed evidence provided at the Design Stage
    OR
    On-site measurements (methodology detailed in BRE IP 23/93 (1)) in the same rooms assessed at Pre-refurbishment stage (required when scale model measurements were carried out at Pre-refurbishment Stage).
Req 2b
  1. Site drawings of the extension showing the impact of daylighting levels of neighbouring properties
  1. As in design stage

Additional information

Relevant definitions

Angle of visible sky
The angle of visible sky u is the angle subtended, in the vertical plane normal to the window, by the visible sky from the centre of the window. Further guidance on how to complete calculations can be found in BS 8206–2:2008, Lighting for buildings—Part 2: Code of practice for daylighting.
Average daylight factor
The average daylight factor is the average indoor illuminance (from daylight) on the working plane within a room, expressed as a percentage of the simultaneous outdoor illuminance on a horizontal plane under an unobstructed CIE ‘standard overcast sky.’
Commission Internationale de l’Eclairage (CIE)
Commission Internationale de l’Eclairage (CIE) is the international standards body for lighting.
No-sky line
The no-sky line divides those areas of the working plane which can receive direct light from the sky, from those which cannot. It is important as it indicates how good the distribution of daylight is in a room. Areas beyond the no-sky line will generally look gloomy.
The working plane is a notional surface, typically at about desk or table height, at which daylight factor or the ‘no-sky line’ is calculated or plotted. For the calculations required under the Hea 1 issue, it is at 0.85 m above the floor.


BREEAM Refurbishment – Domestic Buildings
Reference: SD5072 – Issue: 3.2
Date: 29/02/2016
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