Fusion Park, YeovilDaylight, Sunlight and Overshadowing Study

This Daylight, Sunlight andOvershadowing Study is submittedin support of the PlanningApplication for land at the former Ashley’s Site, Yeovil.

1.0 Introduction

1.1 LHC Architecture has been commis-sioned to provide a daylight and sunlight as-sessment of the proposed mixed use develop-ment on land at West Hendford, Yeovil.

1.2 The objective of this study is to deter-mine the potential impact of the proposed de-velopment on the neighbouring properties and within the site itself.

1.3 The study has been carried out in accord-ance with recommendations of the Building Re-search Establishment (BRE) Digest 209 ‘Site Lay-out Planning for Daylight and Sunlight: a good practice guide’ 1991.

1.4 This assessment considers the impacts of the development in terms of daylight, sunlight and overshadowing.

2.0 The Proposal

2.1 The proposal is for a mixed use develop-ment comprising three units; one A1 food retail ‘discount supermarket’, one A3 ‘family restau-rant/pub’ and one A3 ‘drive-through coffee shop’ on land in Yeovil, Somerset.

2.2 The site is currently disused, and houses the vacant Ashley’s Garage building.

3.0 Policy and Guidance

3.1 The Building Research Establishment (BRE) Digest 209 ‘Site Layout Planning for Day-light and Sunlight: a good practice guide’ 1991, is intended to be advisory and does not contain mandatory standards. It is a document which aims to help rather than constrain the designer. It states:

‘Although it gives numerical guidelines, these should be interpreted flexibly because natural lighting is only one of many factors in site layout design.’

4.0 Assessment Methodology

4.1 This assessment has been carried out us-ing the following information:

- Architect’s drawings of the proposed develop-ment including survey information- Aerial Photography- A 3D Sketch up model has been used with the above information as a basis for the daylight, sunlight and overshadowing commentary pro-vided in this report.

4.2 The study has been carried out in accord-ance with the recommendations of the Building Research Establishment (BRE) Digest 209 ‘Site Layout Planning for Daylight and Sunlight: a good practice guide’ 1991. In general, the BRE tests are based on the requirements of the Brit-ish Standard, BS 9206 Part 2.

4.3 The standards set out in the BRE guide are intended to be used flexibly. In instances where the is a special requirement for daylight or sunlight, higher levels may be deemed neces-sary. In other situations, such as with urban de-velopments, lower daylight and sunlight levels may be unavoidable.

Daylight

4.4 The BRE assessment of daylight states:-

‘If any part of a new building or extension meas-ured in a vertical section, perpendicular to a main window wall of an existing building from the cen-tre of the lowest window, subtends an angle of more than 25 degrees to the horizontal, then the diffuse daylighting of the existing building may be adversely affected.’

4.5 The guide indicates that when some part of a proposed development is opposite the main window wall of an existing building then sections should be drawn perpendicular to the existing window wall. Where information is available the centre point of windows in neigh-bouring properties should be used, where this information is not available a point 2m high on the face of the building should be used.

4.6 If the angle subtended by the new devel-opment at the level of the lowest window is less than 25 degrees then it is unlikely to have a sub-stantial effect on the daylight enjoyed by the ex-isting building. However, if the angle is greater than 25 degrees a more detailed analysis should be undertaken.

4.7 The BRE suggest three methods of meas-uring diffuse daylight:-Vertical Sky Component (VSC)-No-Sky Line-Average Daylight Factor

4.8 Having reviewed the above, there are no main windows in neighbouring dwellings which would be affected by the proposed develop-ment.

Sunlight

4.9 The level of sunlight availability a win-dow can receive is dependent on its orientation as well as external obstructions. The orientation of a window is an important factor in the calcu-lation of sunlight availability as the sun’s path throughout the day moves from east to west within the southern hemisphere. For example, any windows facing due north are unlikely to receive any sunlight apart from in the height of summer, either very early in the morning or late in the evening.

4.10 Where appropriate, the BRE guidelines suggest that the availability of sunlight is as-sessed by calculating ‘Annual Probable Sunlight Hours’ (APSH). APSH calculations are expressed as a percentage of the total probable sunlight hours.

4.15 The BRE have produced sunlight tem-plates for London, Manchester and Edinburgh indicating the Annual Probable Sunlight Hours for these regions. The London template has been selected for this study as the London indi-cator template is the closest of the three avail-able from BRE in terms of latitude.

4.16 When assessing the APSH of a particular window the BRE guidelines suggest the follow-ing criteria:

‘If this window reference point can receive more than one quarter of annual probable sunlight hours... including at least 5% of annual probable sunlight hours during winter months between 21 September and 21 March, then the room should still receive enough sunlight’.

4.17 The maximum number of annual prob-able sunlight hours for the Yeovil orientation is approximately 1,500 hours.

4.18 Therefore, a window would obtain ad-equate sunlight if it achieves an APSH level of at least 25%, of which 5% should be in winter months.

4.19 If the suggested APSH levels are not met, a comparison assessment can be undertaken by calculating the ratio reduction between the baseline and proposed scenarios. The BRE

guidelines suggest that the reduction in sun-lighting may be noticeable to an occupant if the ratio reduction is less than 0.8 times the baseline condition.

4.20 Having reviewed the above, the assess-ment of windows on the neighbouring build-ings is considered unnecessary due to orienta-tion (see Graphic Studies).

5.0 Results of study

5.1 The proposed development will have no effect on windows of neighbouring properties or new units within the development itself.

5.2 The Graphic Studies attachment provides the full results of the Overshadowing Analysis in graphical form.

5.3 For the purpose of this assessment, we have provided shadow plans to show the loca-tion of shadows. The overshadowing has been mapped to the following recommended date:

- 21st March (Spring Equinox)

5.4 In this respect, the proposal complies with BRE standards.

6.0 Conclusion

6.1 The analysis has clearly demonstrated that the proposed development will have little impact upon the light received by its neighbour-ing properties and conforms to BRE standards.

6.2 The siting and design of the proposed units also satisfies all requirements set out in BRE Digest 209 ‘Site Layout Planning for Day-light and Sunlight’.

6.4 The study is based on locational data and architectural drawings as submitted prior to the date of this analysis. The report has been produced solely for the use of the client and no liability to other parties will be accepted.

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Graphic StudiesDaylight, Sunlight and Overshadowing Study

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