Daylight, Sunlight and Overshadowing
Assessment
Northern Terrace Phase 1 - Paxton Development
For Tottenham Hotspur Football Club
August 2016
XCO2 energy
w: www.xco2energy.com :: e: [email protected]
t: +44 (0) 20 7700 1000 :: f: +44 (0) 20 7183 6620
17-18 Hayward’s Place :: Clerkenwell :: London :: EC1R 0EQ
Daylight, Sunlight and Overshadowing
Contents
Executive Summary.......................................................................................... 3
Introduction...................................................................................................... 5
Site..................................................................................................................... 5
Methodology.................................................................................................... 6
Daylight Assessment........................................................................................ 7
Sunlight Assessment....................................................................................... 13
Overshadowing Assessment.......................................................................... 14
Conclusion........................................................................................................ 15
Appendix - Detailed results............................................................................ 16
About us:
XCO2 Energy are a low-carbon consultancy working in the built environment. We are a multi-disciplinary
company consisting of both architects and engineers, with specialists including CIBSE low carbon
consultants, Code for Sustainable Homes, EcoHomes and BREEAM assessors, BRE trained daylight
consultants and LEED accredited professionals.
Issue 01
Issue 02
Remarks
Draft
Final
Prepared by
DB
DB
Checked by
KM
KM
Authorised by
RM
RM
Date
Project reference
29/07/2016
8714
02/08/2016
8714
Northern Terrace Phase 1 - Paxton Development
Issue 03
Issue 04
Daylight, Sunlight and Overshadowing
Executive Summary
Daylight and Sunlight analysis was carried out for
the proposed development at Paxton Road located
within the London Borough of Haringey. This report
outlines the results of the analysis for the planning
application, assessing the daylight and sunlight
impacts on surrounding developments.
The methodology set out in this report is in
accordance with BRE’s “Site Layout Planning for
Daylight and Sunlight, A Guide to Good Practice” by PJ
Littlefair (2011) which is accepted as good practice
by Planning Authorities.
The following assessments were carried out:
• Daylight: 25 Degree Line
• Daylight: Vertical Sky Component
• Daylight: No Sky Line
• Sunlight: Sunlight Access
• Sunlight: Sunlight Overshadowing
Computer modelling software was used to carry
out the assessments. The model used was based on
architectural drawings, desktop research and a 3D
model provided by the design team.
Daylight Assessment
A total of 28 windows from buildings surrounding
the site were highlighted as being in close proximity
to, and facing the proposed development.
Daylighting levels for potentially affected windows
of surrounding developments by the proposed
development were found to be acceptable.
In summary,
• 4 out of 28 windows passed the 25 degree line
test;
• 14 of the remaining 24 windows achieved a VSC
of greater than 27%;
• 4 windows achieved relative VSCs over 0.8 of
their former value
• Two of the remaining six windows are most
likely to serve a dual aspect room, indicating
sufficient daylight received by this room.
• One of the remaining four windows is most
likely to serve a corridor space where daylight
expectation is low.
• The remaining three windows serve the same
room which is expected to result in good levels
of daylight.
Overall, the development is not anticipated to
have any impact on the daylight received by
neighbouring properties.
Northern Terrace Phase 1 - Paxton Development
Daylight, Sunlight and Overshadowing
Sunlight Assessment
A total of 24 windows from buildings surrounding
the site were assessed for sunlight access. The
analysis indicated that 4 of the 24 windows passed
the 25 degree line test. All of the remaining 20
windows apart from two, satisfied the BRE criteria for
annual probable sunlight hours (APSH) and winter
probable sunlight hours (WPSH). The remaining two
windows were found to serve a dual aspect room
where the window on the other aspect is performing
well.
Therefore, the proposed development is not
considered to have any impact on sunlight access to
windows of surrounding developments.
Overshadowing Assessment
One open space was identified to be in close proximity to the proposed development, and has been
included in the overshadowing assessment. All the
assessed space receives at least 2 hours or more of
sunlight on 21 March on at least 50% of its area under
the proposed site condition.
Therefore, the proposed development does not have
a significant impact on sunlight access to the existing
amenity space.
Northern Terrace Phase 1 - Paxton Development
Daylight, Sunlight and Overshadowing
Introduction
Site
This report assesses the daylight, sunlight and
overshadowing impacts the proposed development
at Paxton Road may have on the existing properties
and open spaces surrounding the site.
The proposed development comprises the
construction of a 3 storey above ground unit,
incorporating ticket windows, office space and a
retail unit in the London Borough of Haringey.
The approach is based on the BRE’s “Site Layout
Planning for daylight and sunlight, a Guide to
good practice” PJ Littlefair 2011, which is generally
accepted as good practice by Town and Country
Planning authorities.
Site analysis was carried out to identify any potential
daylight and sunlight impacts on the surrounding
developments. The relevant properties tested
in this report are situated close to the proposed
development, and annotated in the figure below.
It should be noted that although the numerical
values stated by the BRE provide useful guidance to
designers, consultants and planning officials, these
are purely advisory and may vary depending on
context. Dense urban areas, for example, may often
experience greater site constraints when compared
to low-rise suburban areas, and thus a high degree
of obstruction is often unavoidable.
N
796 High Road
794 High Road
790 High Road
Aerial view of surrounding areas of the proposed development (approximate
site area highlighted in pink).
Northern Terrace Phase 1 - Paxton Development
Daylight, Sunlight and Overshadowing
Methodology
The following methodology was used to carry
out the daylight, sunlight and overshadowing
assessments. The methodology is based on the
guidelines set out in the BRE “Site Layout Planning
for Daylight and Sunlight, A Guide to Good Practice”
(2011).
Daylight
1. Daylight to surrounding windows
A plane is drawn at 25 degrees from the horizontal,
at the centre of an existing window. If the new
development intersects with this plane, the internal
daylight levels of the surrounding windows may
be reduced. When an obstruction of the 25 degree
plane occurs, a more detailed assessment involving
the Vertical Sky Component of the affected window
would need to be carried out.
2. Absolute Vertical Sky Component
The Vertical Sky Component is the ratio of the
direct sky illuminance falling on the vertical wall at
a reference point, to the simultaneous horizontal
illuminance under an unobstructed sky. To maintain
good levels of daylight, the Vertical Sky Component
of a window needs to be 27% or greater. If the VSC
is less than 27%, then a comparison of existing
and proposed levels of VSC level would need to be
calculated.
3. Relative Vertical Sky Component
Good levels of daylighting can still be achieved if
VSC levels are within 80% of their former value.
4. % of room with view of the sky (NSL)
Rooms connected to the windows assessed will
not experience a noticeable loss in daylight if
the percentage (%) of the room’s working plane
with view of the sky is over 0.8 of its former
value. The former value could refer either to the
existing development in place or the mirror image
buildings for properties with windows close to site
boundaries.
Northern Terrace Phase 1 - Paxton Development
Sunlight
Access to sunlight (APSH)
The BRE test relates mainly to existing living room
windows, although care should be taken to ensure
that kitchens and bedrooms receive reasonable
amounts of sunlight. Annual Probable Sunlight
Hour (APSH) assessment is carried when there is an
obstruction within the 25 degree line, calculated
from the centre of the window and the proposed
development is situated within 90 degrees due
south of the window.
The APSH assessment states that the existing living
room window should receive at least:
• 25% of annual probable sunlight hours (APSH)
throughout the year;
• 5% of annual probable sunlight hours during the
winter months;
• not less than 80% of it’s former sunlight hours
during either period;
• not more than a 4% reduction in sunlight
received over the whole year (APSH).
The term ‘annual probable sunlight hours’ refers
to the long-term average of the total of hours
during a year in which direct sunlight reaches the
unobstructed ground (when clouds are taken into
account). The ‘winter probable sunlight hours’ is
used to mean the same but only for the winter
period (21 September – 21 March). Note that the
BRE guidance expects the above to be met for living
room windows only.
Overshadowing
Sunlight to Amenity Spaces
Open spaces should retain a reasonable amount of
sunlight throughout the year. The BRE states that
for an amenity space to “appear adequately sunlit
throughout the year, at least half of the area should
receive at least 2 hours of sunlight on 21 March”.
Where this is not achieved, the difference between
the area achieving 2 hours of sun on 21 March
should be no less than 0.8 times its former value.
Daylight, Sunlight and Overshadowing
Daylight Assessment
A total of 28 windows from buildings surrounding
the proposed development were highlighted as
being in close proximity to, and facing the proposed
development.
These buildings include:
• 790 Tottenham High Road - property to the
south-west of the site (windows no. A1-A12)
• 794 Tottenham High Street - property to the
west of the site (windows no. B1-B10)
• 796 Tottenham High Street - property to the
west of the site (windows no. C1-C6).
The daylight analysis follows for each building
individually on the following pages of the report.
Northern Terrace Phase 1 - Paxton Development
Daylight, Sunlight and Overshadowing
790 Tottenham High Road
This building has 12 windows facing the proposed
development. These windows are located on the rear
of the building between ground floor and second
floor. The image to the right shows their location.
The analysis showed that the windows on ground
and first floor did not meet the 25° test, but were
found to achieve very good VSCs with the proposed
development in place. The detailed results of the
analysis are shown in the appendix.
Therefore, the proposed development is not
anticipated to have any impact on the daylight
received by all windows at 790 Tottenham High Road,
to the south-west of the proposed site.
A12
A4
A1
Assessed windows at the rear of 790 Tottenham High
Road
25 degree line from the ground floor windows at 790 Tottenham High Road highlighted in orange (proposed
building highlighted in blue)
Northern Terrace Phase 1 - Paxton Development
Daylight, Sunlight and Overshadowing
794 Tottenham High Road
This building has ten windows facing the proposed
development. These are shown in the image to the
right.
Three windows achieved VSCs higher than 27% and
another three windows passed the relative VSC test.
One of the four windows that do not achieve the
recommended VSCs, most likely serves a corridor
where daylight requirement is lower and the
remaining three windows belong to the same room
and achieve good VSCs for an urban environment,
which indicates that this room will be adequately
daylit.
Overall, the proposed development is not
considered to compromise the daylight received by
these ten windows at 794 Tottenham High Road,
taking into account the unfavourable location of the
ground floor window.
B10
B8
B4
B9
B5
B1
Assessed windows at the rear of 794 Tottenham
High Road
25 degree line from the ground floor windows at 794 Tottenham High Road highlighted in orange (proposed
building highlighted in blue)
Northern Terrace Phase 1 - Paxton Development
Daylight, Sunlight and Overshadowing
796 Tottenham High Road
C1
This building has six windows on the rear of the
building facing the proposed development. These
are shown in the images below and to the right.
C2
The analysis showed that although the windows did
not meet the 25° test, four of the six windows were
found to achieve very good VSCs with the proposed
development in place. The remaining two windows
that did not achieve the required VSCs are part of
the rear extension. This room is most likely serving
a dual aspect and the window on the other aspect
which would be much less affected as it is not facing
the development directly.
Therefore, the proposed development was not
found to have any impact on daylight received by
this building. The detailed results of the analysis are
shown in the appendix.
Assessed windows at the rear of 796 Tottenham
High Road (extension highlighted in dark blue)
C6
C4
C5
C3
2 windows on the
extension
25 degree line from the ground floor windows at 796 Tottenham High Road highlighted in orange (proposed
building highlighted in blue)
Northern Terrace Phase 1 - Paxton Development
10
Daylight, Sunlight and Overshadowing
Daylight Results summary
The table below summarises the findings of
the daylight analysis. It can be seen that the
development does not result in any significant
impact on the neighbouring windows assessed in
detail.
Considering the overall site context, it can be
concluded that the impact of the development is
minimal and well within acceptable limits.
Total number of windows tested
Number of windows passing the 25 degree plane test
Number of windows with a VSC greater then 27%
Number of windows that have a VSC of at least 80% of existing value
Windows that do not meet any of the above criteria but are dual aspect
Windows that serve a corridor where daylight expectation is low
Windows that serve the same room and have good VSCs which results in good daylight levels
Windows that do not meet any of the above criteria
Northern Terrace Phase 1 - Paxton Development
28
4
14
4
2
1
3
0
11
Daylight, Sunlight and Overshadowing
Sunlight Assessment
Sunlight Access Assessment
The BRE guide states that “if a living room of an
existing dwelling has a main window facing within
90o of due south, and any part of a new development
subtends an angle of more than 25o to the horizontal
measured from the centre of the window in a vertical
section perpendicular to the window, then the
sunlighting of the existing dwelling may be ly affected”
A total of 24 windows from buildings surrounding
the site were highlighted as facing the development
and within 90o of due south. These windows belong
to properties included within this assessment.
The analysis indicated that all windows apart from
two, within 90° due south, satisfy the BRE criteria
for sunlight. The two windows that do not meet the
criteria most likely serve a dual aspect room. The
window on the other aspect was found to achieve
good levels of sunlight access. The table below
shows the results summary. The detailed results can
be found in the appendix.
Therefore, the proposed development is not
considered to have any impact on sunlight access to
windows of surrounding developments.
Summary of Sunlight Results for Surrounding Windows
Total number of windows facing south
Number of windows passing the 25 degree plane test
Number of south facing windows with APSH greater than 25% & WPSH greater than 5% or
of at least 80% of their former value
Number of windows with less than 4% annual reduction in APSH
Windows that belong to dual aspect room which will receive good levels of sunlight from
the other aspect
Windows that do not meet any of the above criteria
Northern Terrace Phase 1 - Paxton Development
24
4
18
0
2
0
12
Daylight, Sunlight and Overshadowing
Overshadowing Assessment
An assessment of the sunlight levels of the surrounding amenity spaces that are in close proximity to the
proposed development and may be overshadowed
by the new building was undertaken.
BRE Guidance suggests that the test should be run
on 21 March which is the midpoint between the
summer and winter solstices (equinox). At least half
of each of the amenity areas should receive no less
than 2 hours on 21 March. Where this is not achieved,
a relative test should be carried out to show the are
receiving 2 hours of sunlight is no less than 80% of its
previous value.
A solar access analysis was undertaken on the
closest open space to the north of the proposed
development, as a worst-case approach.
The image below shows that this amenity space
to the north of the site is predicted to receive a
minimum of two hours of sunlight on 21st of March
over more than 50% of its area meeeting the target
recommended in the BRE guide.
The anaylsis result demonstrates that the outdoor
space will receive satisfactory levels of sunlight
access throughout the year.
Potential open area on the north of the proposed site. Shadows plotted between 11:00-14:00
on the 21st of March.
Northern Terrace Phase 1 - Paxton Development
13
Daylight, Sunlight and Overshadowing
Conclusion
The daylight, sunlight and overshadowing analysis
indicates that there will not be a significant impact
on surrounding properties arising from the
proposed Paxton development.
Daylight Assessment
A total of 28 windows from buildings surrounding
the site were highlighted as being in close proximity
to, and facing the proposed development.
Daylighting levels for potentially affected windows
of surrounding developments by the proposed
development were found to be acceptable.
In summary,
• 4 out of 28 windows passed the 25 degree line
test;
• 14 of the remaining 24 windows achieved a VSC
of greater than 27%;
• 4 windows achieved relative VSCs over 0.8 of
their former value
• Two of the remaining six windows are most likely
to serve a dual aspect room, indicating sufficient
daylight received by this room.
• One of the remaining four windows is most
likely to serve a corridor space where daylight
expectation is low.
• The remaining three windows serve the same
room which is expected to result in good levels
of daylight.
windows apart from two, satisfied the BRE criteria for
annual probable sunlight hours (APSH) and winter
probable sunlight hours (WPSH). The remaining two
windows were found to serve a dual aspect room
where the window on the other aspect is performing
well.
Therefore, the proposed development is not
considered to have any impact on sunlight access to
windows of surrounding developments.
Overshadowing Assessment
One open spaces was identified to be in close proximity to the proposed development, and has been
included in the overshadowing assessment. All the
assessed space receives at least 2 hours or more of
sunlight on 21 March on at least 50% of its area under
the proposed site condition.
Therefore, the proposed development does not have
a significant impact on sunlight access to the existing
amenity space.
Overall, the development is not anticipated to
have any impact on the daylight received by
neighbouring properties.
Sunlight Assessment
A total of 24 windows from buildings surrounding
the site were assessed for sunlight access. The
analysis indicated that 4 of the 24 windows passed
the 25 degree line test. All of the remaining 20
Northern Terrace Phase 1 - Paxton Development
14
Daylight, Sunlight and Overshadowing
Appendix - Detailed results
Daylight Assessment
Window no.
25 degree plane
test
VSC tests
Comments
Proposed VSC
>27% ?
Existing
VSC (%)
Relative VSC
>80% ?
25.2%
30.1%
83.7%
A2
-
-
A3
-
-
-
-
-
-
A6
-
-
A7
-
-
A8
-
-
-
-
-
-
-
-
-
-
-
A12
-
-
-
B1
10.4%
14.3%
73.0%
B2
21.8%
32.8%
66.6%
B3
23.5%
32.2%
73.0%
Good VSCs achieved by the windows for
urban environment. All windows serve the
same room which would result in good
daylight
21.9%
31.8%
68.9%
This window most likely serves a corridor
25.3%
29.0%
87.1%
-
-
A1
A4
A5
Further Testing
Required
A9
A10
A11
PASS
B4
B5
B6
Further Testing
Required
B7
>27.0%
>27.0%
Good Levels of Daylight
-
-
B8
27.0%
33.6%
80.2%
B9
20.3%
23.7%
85.8%
B10
>27.0%
-
-
Good Levels of Daylight
C1
13.6%
32.4%
41.9%
13.3%
32.8%
40.5%
These windows serve a dual aspect room
indicating that sufficient
daylight would be received by the room.
-
-
-
-
-
-
-
-
C2
C3
C4
C5
Further Testing
Required
>27.0%
C6
Northern Terrace Phase 1 - Paxton Development
Good Levels of Daylight
Good Levels of Daylight
15
Daylight, Sunlight and Overshadowing
Sunlight Assessment
Window 25 degree
no.
plane test
APSH test
WPSH test
Total %
reduction
< 4% ?
Proposed
APSH > 25% ?
Existing
APSH (%)
Relative
APSH>80% ?
Proposed
WPSH >5% ?
Existing
WPSH (%)
Relative
WPSH
>80% ?
A1
40.0%
-
-
11.4%
-
-
-
A2
40.3%
-
-
12.8%
-
-
-
43.4%
-
-
13.5%
-
-
-
37.7%
-
-
12.3%
-
-
-
40.2%
-
-
11.4%
-
-
-
A6
46.3%
-
-
13.7%
-
-
-
A7
47.1%
-
-
13.5%
-
-
-
A8
45.9%
-
-
12.0%
-
-
-
A9
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
A12
-
-
-
-
-
-
-
B2
26.6%
-
-
8.8%
-
-
-
B4
26.2%
-
-
10.9%
-
-
-
B6
33.5%
-
-
10.5%
-
-
-
B8
29.6%
-
-
9.2%
-
-
-
A3
A4
A5
A10
A11
Further
Testing
Required
PASS
B9
38.8%
-
-
12.1%
-
-
-
B10
33.3%
-
-
9.0%
-
-
-
C1
19.1%
46.0%
41.5%
6.1%
-
-
-
C2
19.8%
46.5%
42.7%
6.5%
-
-
-
C3
33.5%
-
-
7.4%
-
-
-
C4
26.2%
-
-
7.9%
-
-
-
C5
38.0%
-
-
10.0%
-
-
-
C6
32.8%
-
-
11.1%
-
-
-
Northern Terrace Phase 1 - Paxton Development
Comments
Good
sunlight
levels
Serves a
dual aspect
room where
the window
on the other
aspect is
performing
well.
Good
sunlight
levels
16