daylight and sunlight report - north · pdf file8 rpsgroup.com 4 method of assessment general...

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19 December 2013

DAYLIGHT AND SUNLIGHT REPORT

BOTLEY DISTRICT CENTRE

PROPOSED MIXED-USE REDEVELOPMENT

Our Ref: N9064 RPS Cathedral Buildings

Dean Street

Newcastle upon Tyne

Tyne & Wear

NE1 1PJ

Tel: 0191 232 6306 Fax: 0191 232 5359 Email: [email protected]

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QUALITY MANAGEMENT

Prepared by: J Bainbridge

Authorised by: S Long

Date: 19th

December 2013

Project Number/Document Reference:

N9064

COPYRIGHT © RPS

The material presented in this report is confidential. This report has been prepared for the exclusive use of [Doric Properties and shall

not be distributed or made available to any other company or person without the knowledge and written consent of RPS.

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CONTENTS

1 PREFACE ............................................................................................................................................... 4

2 EXECUTIVE SUMMARY ........................................................................................................................ 5

3 INTRODUCTION ..................................................................................................................................... 7

4 METHOD OF ASSESSMENT ................................................................................................................. 8

General .................................................................................................................................................... 8

Detailed guidance for daylight ................................................................................................................. 9

Detailed guidance on sunlight ............................................................................................................... 10

5 SITE ....................................................................................................................................................... 11

6 MODEL .................................................................................................................................................. 14

Model Sources ....................................................................................................................................... 15

7 DAYLIGHT ANALYSIS ......................................................................................................................... 16

8 SUNLIGHT ANALYSIS ......................................................................................................................... 18

9 CONCLUSION ...................................................................................................................................... 19

Daylight .................................................................................................................................................. 19

Sun-path ................................................................................................................................................ 19

Final Comment ...................................................................................................................................... 19

10 APPENDIX A – PRELIMINARY CHECK DIAGRAMS ......................................................................... 20

11 APPENDIX B – VSC RESULTS ........................................................................................................... 21

12 APPENDIX C – APSH RESULTS ......................................................................................................... 29

13 APPENDIX D– SUNLIGHT DIAGRAMS .............................................................................................. 33

14 APPENDIX D – SUN-PATH DIAGRAMS ............................................................................................. 37

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1 PREFACE

NON-DISCLOSURE This document contains confidential information. In consideration of RPS disclosing such

confidential information this document should be held and maintained in confidence and should

only be disclosed to:

1. Professional advisors to the client

2. The Local Authority for the site location

3. The Environment Agency

4. Clients permitted assignees established by written assignment; and

5. Professional advisors of permitted assignees

This document is issued only to the organisations stated above and on the understanding that this

practice is not held responsible for the action of others who obtain any unauthorised disclosures of

its contents or place any reliance on any part of its findings, fact or opinions, be they specifically

stated or implied.

The confidential information in this document shall only be used for the intended purpose.

FREEDOM OF INFORMATION

Copies of this document may come into the possession of organisations designated under the

Freedom of Information Act 2000. Organisations designated in the ‘Act’ are requested to respect

the above statements relating to confidentiality and copyright.

ENQUIRIES

Any enquiries regarding this document shall be directed to RPS:-

Telephone No: 0191 232 6306

E-Mail: [email protected]

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2 EXECUTIVE SUMMARY

RPS have been commissioned by Doric Properties to evaluate the access to daylight and sunlight

to the surrounding buildings, that will be affected by the new proposed development at Botley,

Oxford.

In considering the development potential and the quality of amenity for the surrounding properties

once the scheme has been implemented, an analysis of daylight and sunlight was carried out in

accordance with the ‘Site Layout Planning for Daylight and Sunlight: a Guide to Good Practice’, by

BRE 2011.

The BRE Guide is intended for designers, clients, consultants and planning officials. The advice

here is not mandatory and this document should not be seen as an instrument of planning policy.

It was determined that most of the surrounding buildings receive a VSC (Vertical Sky Component)

of less than 27% recommended by the BRE Guide. Therefore the existing view is compared

against the view with the new proposed extension.

If the comparison shows that the reduction of light to the surrounding buildings is less than 20% or

0.8 times its former value then this is deemed as being in accordance with the recommendations

set out in the BRE Guide.

In most of the cases analysed on West Way there is no significant reduction in light to the windows

of the buildings. In the houses opposite the tallest residential section of the development (No 62 –

68) there is a reduction in daylight to the surrounding residential properties to slightly below the

standards set out in the BRE guide meaning that the occupants of these properties may notice the

reduction in daylight from the ground floor windows. It must be noted however that a significant

proportion of these residential properties have large trees in their front garden that already restrict

the amount of daylight/sunlight reaching the properties therefore the effect of the proposed

development would be less noticeable.

When analysing the sunlight available to all of the residential properties analysed on West Way the

results prove that they have adequate provision throughout the year according to the

recommendations of the guide.

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The church in the centre of the development would not receive the recommended amount of

Daylight & Sunlight as stated by the BRE Guide and the reduction in light is more than the

recommended 20% so will be noticed by the occupants.

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3 INTRODUCTION

The new proposed development at Botley, Oxford has been assessed in accordance with the ‘Site

Layout Planning for Daylight and Sunlight: a Guide to Good Practice’, by BRE 2011.

RPS was commissioned by Doric Properties to assess the impact of the new proposed

development upon the access to daylight and sunlight to the windows of the surrounding buildings.

The new proposed development is a multi-use community space including supermarket, car park,

cinema, restaurants and shops and student accommodation.

The method used to assess the impact of the new proposed development is outlined in this report

together with the results and conclusions. All buildings have been considered where they are

deemed to affect the results of the calculation.

In relation to sunlight, the criteria given calculates the annual probable sunlight hours (APSH)

which considers the amount of sun available in both the summer and winter for each given window

which faces the proposed new development. Summer is considered to be the six months between

March 21st and September 21st and winter the remaining months.

A selection of residential properties situated on West Way have been selected for this analysis

which have windows where their Daylight or Sunlight could be affected by the new proposed

development.

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4 METHOD OF ASSESSMENT

General

BRE Report 209, “Site Layout Planning for Daylight and Sunlight – A Guide to Good Practice” is

intended for building designers, clients, consultants and planning officials and provides guidance

on site layout to provide good natural lighting within a new development; safeguarding of daylight

and sunlight within existing buildings nearby; and the protection of day-lighting of adjoining land for

future development.

It is important to note that the advice given in the BRE report is not mandatory. Specifically, in the

introduction to the report, it states that: “The guide is intended for building designers and their

clients, consultants and planning officials. The advice given is not mandatory and the guide should

not be seen as an instrument of planning policy; its aim is to help rather than constrain the

designer. Although it gives numerical guidelines, these should be interpreted flexibly since natural

lighting is only one of many factors in site layout design. In special circumstances the developer or

planning authority may wish to use different target values. For example, in a historic city centre, or

in an area with modern high rise buildings, a higher degree of obstruction may be unavoidable if

new developments are to match the height and proportions of existing buildings.”

The BRE guide states that the guidelines are to be used for adjoining/adjacent dwellings where

daylight is required including living rooms, kitchens and bedrooms. Windows to bathrooms, toilets,

store rooms and circulation spaces and garages need not be analysed. Non-domestic buildings

where the occupants have a reasonable expectation of daylight should also be considered,

although these are usually less sensitive than dwellings

The BRE guide sets out criteria against which an assessment may be made of the levels of

daylight / sunlight and the impact that development may cause.

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Detailed guidance for daylight

The BRE guidelines provide three main methods of calculation for daylight/sunlight. It should be

noted that the report emphasises that the numerical values given are purely advisory.

Preliminary Check 1 – The guide provides preliminary guidance and looks at the distance

between the new development and the existing buildings being analysed and addresses whether

the existing building still receives enough skylight. If the distance between the buildings is 3 times

the height difference between the ground floor window and the top of the new development then

the loss of light need not be analysed as the loss of light will be small. If the distance is less than 3

times the height difference a modified form of the procedure is adopted.

Preliminary Check 2 - A section is drawn of the existing buildings and proposed development and

a line is drawn perpendicular from the ground floor window centre, and another drawn from the

window to the top of the development. If this exceeds the recommended value of 25º from the

centre of the window being assessed then the window is deemed to be at risk of losing light. If this

is the conclusion then the Vertical Sky Component (VSC) then has to be calculated.

VSC - The BRE Guide criteria states “if the calculated Vertical Sky Component is greater than

27% then enough skylight should still be reaching the window of the existing building. Any

reduction below this should be kept to a minimum. If the VSC with the new development in place is

both less than 27% and less than 0.8 times its former value occupants of the existing building will

notice the reduction in the amount of skylight. The area lit by the window is likely to appear more

gloomy and electric lighting will be needed more of the time”.

DD - The Daylight Distribution is also referred to as ‘no sky-line’ method and takes the analysis a

step further in looking at where in the room daylight is received at the working plane, for example

desk or kitchen worktop height. After a development is complete, the area of a room with visible

sky should, ideally be 0.8 times or more of the former area on the working plane prior to the

development. There is no absolute minimum area given by the BRE report. This is to be carried out

if the room layouts are known.

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Detailed guidance on sunlight

The BRE guide advises that in residential properties the main requirement for sunlight is in the

living room and is values at all times of the day. Conservatories are also deemed to require

sunlight, Bedrooms and kitchens are viewed as less important. Winter sunlight is also considered

due to the warming affect it can have on properties and therefore reduces space heating loads. In

new developments care should be taken to safeguard the sunlight to existing properties as people

may notice the loss of sunlight to their homes and if extensive it will usually be resented.

With regard to assessing the levels of sunlight, the BRE report gives recommendations that it is

only those windows that face within 90 degrees of due South that will enjoy significant amounts of

sunlight therefore assessments are required for these windows only. Sunlight is measured in terms

of Annual Probable Sunlight Hours (APSH). The assessment calculates the APSH for a point in the

centre of each window. Their recommendations state that at least a quarter of annual probable

sunlight hours (represented as 25% in the results tables) should be received annually, including at

least 5% of annual probable sunlight hours during the winter months, between 21 September and

21 March. Any reduction in APSH (annual or winter) should be kept to a minimum and not less

than 0.8 its former value or the occupants will notice the loss of sunlight. If the reduction is less

than 4% annually the room may appear colder and less cheerful and pleasant.

The garden spaces of the residential properties have not been assessed.

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5 SITE

5.1 Development

The site is located within Botley, a settlement comprised of areas within both North Hinksey Parish

Council and Cumnor Parish Council’s administrative areas. Botley effectively forms the western

arm of Oxford.

The site is located wholly within North Hinksey Parish Council.

Figure 5.1 Current site

Figure 5.2 Proposed development

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5.2 Affected residence

The buildings that could be affected by the new proposed development are located to the North of

the development and have windows that would face the proposed building. They are all residential

properties of varying type and size.

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Figure 5.3 Typical residential properties on West Way

There is a church in the centre of the site that the development wraps around that has a stained glass

window that is to be analysed.

Figure 5.4 Church

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6 MODEL

To analyse the potentially effected buildings a three dimensional model is constructed to represent

the new proposed development and the affected buildings. Each window of the potentially effected

buildings is analysed to measure the existing Daylight and Sunlight potential and the proposed

Daylight & Sunlight potential.

Fig 6.1 Model of existing

Figure 6.2 Model of proposed

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Model Sources

• The model has been created from the sketch up 3D model received 5th December 2013.

• Window positioning has been taken from internet map images. Please note RPS will not

accept any potential liabilities created by any inaccuracies arising from the use of

approximate/inaccurate information provided to us by a third party or where requisite

information is missing.

Figure 6.3 – The image above shows window references for No 62 and 64 West Way which

are referenced in the VSC and APSH results tables.

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7 DAYLIGHT ANALYSIS

Preliminary Check 1

“Loss of daylight to existing widows need not be analysed if the distance of each part of the

new development from the existing window is three or more times its height above the

centre of the existing window.”

When considering the preliminary review suggested by BRE we can conclude the following.

There is 16.48m height difference between the ground floor window in the Property at the north

east of the development (numbers 62-70) and the top of the proposed development. 3 times this is

49.4m. The actual horizontal separation is 32.48m therefore further analysis is required.

Diagrams are shown in Appendix A

Preliminary Check 2

“If the angle drawn from the ground floor window to the uppermost part of the proposed

building is less than 25o, the loss of daylight will be small.”

When considering the preliminary review suggested by BRE we can conclude the following.

The property closest to the tallest section of the building are only very slightly in excess of the 25o

guidance stated by BRE therefore the reduction in daylight should be small.

Diagrams are shown in Appendix A

To provide a better understanding of the effect that the proposed building has on the existing

residential properties, further analysis has been carried out.

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Vertical Sky Component (VSC)

Using the model it is possible to produce a series of Waldram Diagrams that assist in calculating

the Vertical Sky Component (VSC) and the Available Sunlight Hours for both the existing model

and the proposed model.

“If a window has a VSC of 27% or greater it is deemed that the window should be receiving

enough sky-light. If the VSC value is below the 27% then this value should be calculated

against the previous daylight potential. If the difference is no less than 0.8 times its former

value, or 80%, then it is deemed that occupants of the existing buildings will not notice the

reduction in light.”

The VSC results show that there is a reduction due to the proposed development, however the

resultant figures are either above the recommended 27% or are within 5% of this figure for the

majority of residential properties. The ground floor windows in numbers 62, 64, 66 and 68 West

Way have a VSC 7% lower than the limit set out in the BRE Guide and the figures are 0.73 times

the original. Therefore the ground floor windows of these properties may notice a slight reduction in

daylight.

See Appendix B for the Waldram Diagrams for a selection of the properties on West Way.

We therefore conclude that in all instances the proposed development does not significantly

impact on the daylight amenity to the residential properties surrounding the site.

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8 SUNLIGHT ANALYSIS

BS 8206-2 Code of practice for day-lighting recommends that at least 25% of APSH (Annual

Probable Sunlight Hours) be available in the summer moths including at least 5% during the winter.

See Appendix C for the APSH results with Sunlight Diagrams.

The results show that all properties pass the BRE criteria. The annual APSH for all properties is

above 25% before and after the introduction of the proposed development. The winter APSH’s

before and after the proposed development are above 5%.

We therefore conclude that in all instances the proposed development does not impact on the

sunlight availability to the residential properties surrounding the site.

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9 CONCLUSION

Daylight

The results show that when the new proposed development all of the windows analysed receive a

VSC in excess of the 27% recommended by the BRE Guide (or within 7% of this figure).

Sunlight

The models produced have been used to produce available sunlight hour figures. This uses a

similar method as the Waldram diagram method, however it plots the sun path across the sky and

measures how much of the sunlight is available given the obstructions and size and shape of the

windows assessed.

All of the windows assessed have an adequate amount of sunlight available to them according to

BS 8206-2.

Sun-path

Sun-path diagrams can be produced for all properties analysed and show the suns path as seen

from each window during the summer, spring and winter solstice. The houses opposite the

development have reduced sunlight in the winter and some in the spring mornings with the

summer being unaffected.

An example is shown in Appendix D

Final Comment

We would conclude that the daylight and sunlight levels would not be significantly affected in any

the windows of the residential properties on West Way. Most of the properties on the street pass

the criteria set out in the BRE guide and therefore the residents of these properties are unlikely to

notice any difference in the daylight and sunlight to their properties.

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10 APPENDIX A – PRELIMINARY CHECK DIAGRAMS

Typical cross section of residential properties and proposed development

Figure 10.1: 25 degree angle check

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11 APPENDIX B – VSC RESULTS

The Waldram Diagram is an alternative method to the skylight indictor, which can be used to

assess complex scenarios where the obstruction is complex in shape or the results provide an

insufficient conclusion.

The shape of the building is projected onto a template diagram. After plotting all structures visible

from the position being assessed, the area of remaining sky is used to calculate the Vertical Sky

Component.

Floor Ref. Window

Ref. Scenario VSC Difference Pass/Fail

Within 5%

of VSC

No

60

Ground W1 Existing 35.44 0.74 FAIL PASS

Proposed 26.29


Proposed 26.63

Ground W3 Existing 35.9 0.75 PASS

Proposed 27.05

First W1 Existing 36.48 0.76 PASS

Proposed 27.73


Proposed 28.04


Proposed 28.33

No

62

Ground W1 Existing 34.95 0.73 FAIL FAIL

Proposed 25.48


Proposed 25.51


Proposed 25.51


Proposed 27.14


Proposed 27.16

No

64


Proposed 25.38


Proposed 25.33


Proposed 25.45


Proposed 27.18


Proposed 27.15

Fig 11.1: VSC results for No. 60-64 West Way

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Floor Ref. Window


Within 5%

of VSC

No

66


Proposed 25.49


Proposed 27.22

No

68


Proposed 25.5


Proposed 27.1

No

70

Ground W1 Existing 35 0.73 FAIL PASS

Proposed 25.65


Proposed 27.43

First W2 Existing 36 0.75 PASS

Proposed 27.16

No

72


Proposed 25.77


Proposed 27.42


Proposed 27.56

No

74


Proposed 26.05


Proposed 25.78


Proposed 27.9


Proposed 27.35

No

76


Proposed 26.72


Proposed 26.34


Proposed 28.29


Proposed 28.11

No

80


Proposed 32.06


Proposed 33.99

No

82


Proposed 32.36


Proposed 34.14


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Floor Ref. Window


No

84


Proposed 32.08


Proposed 33.5


Proposed 33.5

No

86


Proposed 31.71


Proposed 32.43


Proposed 33.16

No

88


Proposed 30.79


Proposed 32.35


Proposed 30.51

No

90


Proposed 30.98


Proposed 32.85


Proposed 32.74


Proposed 32.67


Proposed 32.55

No

92


Proposed 30.47


Proposed 31.68

No

94


Proposed 33.36


Proposed 35.53


Proposed 34.72


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The Church stained glass windows have been analysed.

Figure 11.4: Image of church stained glass windows used in analysis

Floor Ref. Window


Ch

urch

Ground W1 Existing 33.1 0.24 FAIL

Proposed 8.07

Ground W2 Existing 33 0.25

FAIL

Proposed 8.22

Ground W3 Existing 32.24 0.27

FAIL

Proposed 8.71

Fig 11.5: VSC results for Church stained glass windows

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No.60 West Way

Fig 11.6: Waldram diagram for No. 60 West Way

The diagram above is for one of the ground floor windows of number 60 West Way.

Green depicts the existing and blue is the proposed development.

The VSC from the window of this property is 26.63 which is within 2% of the required 27%.

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No.66 West Way


The diagram above is for the ground floor window.

The VSC is 25.49% which is within 6 % of the target figure. It can be seen that the tallest section of

the proposed development is causing the problem. Any reduction in this will increase the VSC.

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No.72 West Way



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No.80 West Way



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12 APPENDIX C – APSH RESULTS

Available Sunlight Hours

Floor Ref Window Ref Annual % Diff % Pass/Fail Winter % Diff % Pass/Fail

No

60

Ground W1 73 0.82 PASS

23 0.61 PASS

60 14


23 0.61 PASS

61 14


25 0.56 PASS

61 14

First W1 73 0.85 PASS

23 0.61 PASS

62 14


27 0.59 PASS

64 16


26 0.62 PASS

65 16

No

62


24 0.54 PASS

58 13


23 0.57 PASS

59 13


23 0.52 PASS

55 12


25 0.64 PASS

63 16


24 0.63 PASS

60 15

No

64

Ground W1 75 0.76 PASS 25 0.52 PASS

57 13


58 13


57 13

First W1 72 0.83 PASS 24 0.67 PASS

60 16

First W2 76 0.82 PASS 25 0.64 PASS

62 16

Fig 12.1: APSH results for No. 60-64 West Way

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Floor Ref Window Ref. Annual %

Diff % Pass/Fail Winter% Diff% Pass/Fail

No

66


23 0.57 PASS

58 13


23 0.61 PASS

61 14

No

68


24 0.58 PASS

59 14


24 0.63 PASS

62 15

No

70


24 0.58 PASS

59 14


26 0.69 PASS

65 18


26 0.58 PASS

62 15

No

72


25 0.56 PASS

60 14


26 0.65 PASS

64 17


26 0.69 PASS

64 18

No

74


27 0.59 PASS

60 16


25 0.56 PASS

58 14


28 0.64 PASS

64 18


26 0.65 PASS

61 17

No

76


26 0.62 PASS

61 16


26 0.58 PASS

61 15


27 0.67 PASS

65 18


28 0.68 PASS

65 19

No

80


26 0.85 PASS

70 22


26 0.92 PASS

73 24

No

82


26 0.85 PASS

68 22


26 0.92 PASS

76 24


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Floor Ref Window Ref. Annual %

Diff % Pass/Fail Winter % Diff % Pass/Fail

No

84


24 0.79 PASS

67 19


25 0.88 PASS

71 22


24 0.92 PASS

74 22

No

86


27 0.81 PASS

71 22


27 0.78 PASS

72 21


27 0.85 PASS

73 23

No

88


27 0.74 PASS

73 20


27 0.78 PASS

74 21


20 0.80 PASS

63 16

No

90


26 0.73 PASS

73 19


27 0.78 PASS

75 21


28 0.79 PASS

75 22


28 0.82 PASS

77 23


27 0.81 PASS

76 22

No

92


23 0.74 PASS

67 17


27 0.74 PASS

74 20

No

94


27 0.89 PASS

71 24


28 0.89 PASS

79 25


28 0.82 PASS

76 23


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Floor Ref Window Ref Annual % Diff % Pass/Fail Winter % Diff % Pass/Fail

Ch

urch


16 0.06 PASS

11 1


18 0.06 PASS

15 1


19 0.16 PASS

18 3

Fig 12.4: APSH results for Church stained glass windows

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13 APPENDIX D– SUNLIGHT DIAGRAMS

The Sunlight Diagram is the method used to assess the amount of sunlight hours available for the

assessed window. It is assessed by plotting the sunlight path across the sky with fixed known sun

points.

Any areas where a sun point is obstructed by a building or another object this sun point is not

counted and excluded from the calculation.

No.60 West Way

Fig 13.1: APSH diagrams for No. 60 West Way

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Green depicts the existing and blue is the proposed development

The blue dots represent the winter sun and the yellow dots depict summer sun.

No.66 West Way


The diagram above is for the ground floor conservatory window.

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No.72 West Way



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No.80 West Way



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14 APPENDIX D – SUN-PATH DIAGRAMS

Sun-path diagrams show the suns path as seen by each window analysed.

The sun-paths below are shown for No.60 West Way.

Fig 14.1: Sunpath diagrams for No. 60 West Way

The green depicts the existing building, and the blue shows the proposed development as seen

from the ground floor window of No. 60. It clearly shows that the sun is blocked to the window in

the morning during the spring months from 8.30 – 11am.

During the winter months the ground floor windows will experience intermittent sunlight from 9am –

10am and after 12pm which will no longer be available.

With both the existing and proposed buildings in the summer months, the ground floor windows

achieves full sunlight throughout the day.

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Looking at the sunlight available at the ground floor window of number 66 it can be seen that the

summer sun is not affected, the spring sunlight is only very slightly reduced I the mornings and the

winter sunlight is affected throughout the day.

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As you go further down the street the effect of the proposed development is reduced. The spring

sun before 8am and the winter sun after 1pm is reduced but remains the same at all other times.

daylight and sunlight report - north · pdf file8 rpsgroup.com 4 method of assessment general...

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