HomeMy WebLinkAbout2560419 - F.I. Received Doc. - Overshadowing Study
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Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Report For: CMD Architects
Project No: 21091
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 2
Version History
Document created by:
Integrated Environmental Solutions Limited
International Sustainability Consulting Developers of the IES <Virtual Environment>
Issued For: Prepared by: Checked by:
Request for Further Information Chandrasekhar Rachabattuni, Project Manager Douglas Bell, Consultancy Manager
Version: Date: Revision Details: Approved by:
P1-02 02-06-26 Draft For Comment Douglas Bell
P1-03 03-06-26 Final Report Douglas Bell
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
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Table of Contents
1 Executive Summary ............................................................................................................ 4
2 Introduction ....................................................................................................................... 8
3 BRE – Site Layout Planning for Daylight and Sunlight (3rd Edition) ................................... 9
4 Methodology .................................................................................................................... 10
5 Shadow Analysis............................................................................................................... 16
6 Sunlight to Amenity Spaces ............................................................................................. 32
7 Sunlight to Existing Buildings ........................................................................................... 39
8 Daylight to Existing Buildings ........................................................................................... 44
9 Conclusion ........................................................................................................................ 51
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 4
1 Executive Summary
This report summarises the analyses undertaken to quantify the Sunlight and Daylight
performance of the proposed two storey development located at Knockcarrick in County
Monaghan. The report focuses on measuring the daylight and sunlight impact to the
surrounding dwellings in response to a further information request from the local authority
which was as follows .
“(a) A commensurate Sunlight/Daylight/Overshadowing Study showing impacts on the
western neighbouring dwelling and garden at specific dates and times throughout the year.
Same should focus on the rear windows and private amenity space of the adjoining dwell ing.”
1.1 Planning Authority Guidelines
Where daylight is concerned, The Government of Ireland Planning Design Standards for
Apartments 2025 refers to the Government of Ireland Sustainable Residential Development
and Compact Settlements Guidelines 2024 Section 5.3.7 (b) Daylight, which states th e
following:
“(b) In cases where a technical assessment of daylight performance is considered by the
planning authority to be necessary, regard should be had to quantitative performance
approaches to daylight provision outlined in guides like A New European Standard fo r
Daylighting in Buildings IS EN17037:2018, UK National Annex BS EN17037:2019 and the
associated BRE Guide 209 2022 Edition (June 2022), or any relevant future standards or
guidance specific to the Irish context.”
“In drawing conclusions in relation to daylight performance, planning authorities must weigh
up the overall quality of the design and layout of the scheme and the measures proposed to
maximise daylight provision, against the location of the site and the ge neral presumption in
favour of increased scales of urban residential development. Poor performance may arise due
to design constraints associated with the site or location and there is a need to balance that
assessment against the desirability of achieving wider planning objectives. Such objectives
might include securing comprehensive urban regeneration or an effective urban design and
streetscape quality.”
As such the following section details out the standards adhered to within this report that align
with the planning authority guidelines as outlined above.
To note, all methodologies have been employed for completeness to ensure appropriate and
reasonable regard has been taken to address all assessments under all of the different
standards. For clarity these are listed below and the following Section 1.2 den otes which
standard is applicable for each assessment type:
• BRE Guide –3rd Edition of BR 209 BRE Site Layout Planning for Daylight and Sunlight RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 5
1.2 Reference Standards & Summary of Assessments Undertaken
The various daylight and sunlight assessments that were undertaken using the IES VE software
are based on a number of different standards which are referenced in the individual sections
of this report. For clarity, the assessments that were undertaken are summarised below as
well as the reference standards that were used for each (where applicable):
• Shadow Analysis
o Assessed using shadow images cast at key times throughout the year, i.e. March
21st, June 21st and December 21st to determine if any overshadowing impact occurs
and to what extent to any Existing neighbouring dwellings in accordance with the
BRE Guide (3rd Edition).
• Sunlight to Amenity Spaces
o Assessed using annual Solar Exposure calculations to determine any impact to
Existing amenities and the sunlight received and also to assess the proposed
developments amenity spaces to derive how much sunlight they can expect to
receive in accordance with the BRE Guide (3rd Edition).
• Sunlight to Existing Buildings
o Assessed using the Annual Probable Sunlight Hours (APSH) method in accordance
with the BRE Guide (3rd Edition) - to determine any impact to sunlight received to
the Existing neighbouring building main living areas.
• Daylight to Existing Buildings
o Assessed using the Vertical Sky Component (VSC) method in accordance with the
BRE Guide (3rd Edition) - to determine any impact to existing daylight received to
the Existing building neighbouring the site.
The following can be concluded based on the assessments undertaken:
1.3 Shadow Analysis
The shadow analysis illustrates different shadows being cast at key times of the year (March
21st, June 21st and December 21st) for the Existing Situation and the Proposed Scheme. The
results from the study are summarised as follows:
Neighbouring House – North
Minor additional shading noted in December* (1000-1200). No additional shading noted at
any other period.
30 Knockcarrick - West
Minor additional noted in the Morning of March and June 0800. No additional shading
noted at any other period. RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 6
* Overshadowing can be expected in December when the sun is lower in the sky and shadows
cast are much longer. Although this is the case, overshadowing is least noticeable during the
winter months as there is a lot less sunlight available at this time of ye ar and so the overall
impact is vastly reduced.
The potential shading impact is quantified via the “Sunlight to Amenity Spaces” and “Daylight
to Existing Buildings” section of this report.
1.4 Sunlight to Amenity Spaces
As outlined in Section 3.3.17 of the BRE Guide (3rd Edition), for a space to appear adequately
sunlit throughout the year, at least half of the garden or amenity area should receive at least
2 hours of sunlight on March 21st. In the case of Existing amenity spaces, if they are already
below the 50% threshold then the BRE recommends the results kept to within 80% of the
existing situation.
Existing Amenity Spaces
On March 21st, all of the existing neighbouring amenity spaces tested will receive the same
levels of sunlight with the proposed development in place when compared to the existing
scenario. All the amenity spaces tested complying with the recommendations in the BRE
Guide outlined above and highlight a negligible impact to neighbour’s sunlight received
throughout the year.
1.5 Sunlight to Existing Buildings
This study considers the proposed scheme and tests if the Annual Probable Sunlight Hours
(APSH) results for the living room windows (existing properties) are greater than 25% annual
and 5% winter sunlight or are greater than 0.8 times their former value wi th the proposed
development in place or the reduction in sunlight across the year is less than 4% with the
proposed development in place.
When compared to the Existing Scheme, 100% of the tested points (3 no.) meet the BRE
recommended values. These results highlight that the proposed development will have
negligible impact to the sunlight received to these existing neighbouring properties.
1.6 Daylight to Existing Buildings
This study considers the Proposed Scheme and tests if the VSC results are greater than 27%
or not less than 0.8 times the value of the Existing Situation.
When compared to the Existing Situation, o f the 6 no. points tested, 100% have a Proposed
VSC value greater than 27% or not less than 0.8 times their former value compared to the
Existing Situation, thus complying with the BRE Guidelines. The results highlight a negligible
impact to the neighbours where daylight is concerned. RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 7
1.7 Observations
It is important to note that the recommendations within the BRE Guide (3 rd Edition) itself
states “although it gives numerical guidelines these should be interpreted flexibly because
natural lighting is only one of many factors in site layout design”, Although this is true
appropriate and reasonable regard has still been taken to the BRE guide.
Whilst the results shown relate to the criteria as laid out in the BRE Guide (3rd Edition), it is
important to note that the BRE targets are guidance only and should therefore be used with
flexibility and caution when dealing with different types of sites.
In addition, BRE Guide 3rd Edition also notes:
“This report is a comprehensive revision of the 2011 edition of Site layout planning for
daylight and sunlight: a guide to good practice. It is purely advisory and the numerical target
values within it may be varied to meet the needs of the development and its location.”
Taking all of the above information into account and based on the results from each of the
assessments undertaken, the proposed development performs well when compared to the
recommendations in the BRE Guide 3rd Edition when considering the potential impacts to the
existing neighbouring properties. Overall, there will be a negligible impact to the neighbours
when considering sunlight and daylight if the proposed development is built. RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 8
2 Introduction
This report summarises the analyses undertaken to quantify the Sunlight and Daylight
performance of the proposed two storey development located at Knockcarrick in County
Monaghan. The report focuses on measuring the daylight and sunlight impact to the
surrounding dwellings in response to a further information request from the local authority
which was as follows.
“(a) A commensurate Sunlight/Daylight/Overshadowing Study showing impacts on the
western neighbouring dwelling and garden at specific dates and times throughout the year.
Same should focus on the rear windows and private amenity space of the adjoining dwell ing.”
2.1 Development Description
I, Raymond Prunty, intend to apply for Permission for a development at 31 Knockcarrick,
Mullaghduff (DED: Carrickaslane), Co. Monaghan. The development will consist of permission
to separate section of existing two storey detached dwellinghouse and extend same to form
2 No. two storey semi-detached units comprising:
1) Renovation to existing dwellinghouse to form a 4 bedroom two storey dwellinghouse.
2) Extension to separated section to form a new 3 bedroom two storey dwellinghouse and all
associated site development works.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 9
3 BRE – Site Layout Planning for Daylight and Sunlight (3rd Edition)
Access to daylight and sunlight is a vital part of a healthy environment. Sensitive design should
provide sufficient daylight and sunlight to new residential developments while not
obstructing light to existing homes nearby.
The 3rd Edition of the BR 209 BRE Site Layout Planning for Daylight and Sunlight, advise on
planning developments for good access to daylight and sunlight and is widely used by local
authorities to help determine the performance of new developments.
3.1 Impact Classification Discussion
BRE guidance in Appendix H (BRE Guide 3 rd Edition) – Environmental Impact Assessment
suggests impact classifications as minor, moderate and major adverse. It provides further
classifications of these impacts with respect to criteria summarised in the table below.
Where the loss of skylight or sunlight fully meets the guidelines in the BRE guide (3 rd Edition),
the impact is assessed as negligible or minor adverse. Where the loss of skylight or sunlight
does not meet the BRE guidelines, the impact is assessed as minor, moderate or major
adverse.
Impact Description
Negligible adverse
impact
• Loss of light well within guidelines, or
• only a small number of windows losing light (within the guidelines) or
limited area of open space losing light (within the guidelines)
Minor adverse
impact (a)
• Loss of light only just within guidelines and
o a larger number of windows are affected or
o larger area of open space is affected (within the guidelines)
Minor adverse
impact (b)
• only a small number of windows or limited open space areas are affected
• the loss of light is only marginally outside the guidelines
• an affected room has other sources of skylight or sunlight
• the affected building or open space only has a low-level requirement for skylight
or sunlight
• there are particular reasons why an alternative, less stringent, guideline should
be applied
Major adverse
impact
• large number of windows or large open space areas are affected
• the loss of light is substantially outside the guidelines
• all the windows in a particular property are affected
• the affected indoor or outdoor spaces have a particularly strong requirement
for skylight or sunlight (living rooms / playground)
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 10
4 Methodology
4.1 Planning Authority Guidelines
Where daylight is concerned, The Government of Ireland Planning Design Standards for
Apartments 2025 refers to the Government of Ireland Sustainable Residential Development
and Compact Settlements Guidelines 2024 Section 5.3.7 (b) Daylight, which states th e
following:
“(b) In cases where a technical assessment of daylight performance is considered by the
planning authority to be necessary, regard should be had to quantitative performance
approaches to daylight provision outlined in guides like A New European Standard fo r
Daylighting in Buildings IS EN17037:2018, UK National Annex BS EN17037:2019 and the
associated BRE Guide 209 2022 Edition (June 2022), or any relevant future standards or
guidance specific to the Irish context.”
To note, all methodologies have been employed for completeness to ensure appropriate and
reasonable regard has been taken to address all assessments under all of the different
standards. For clarity these are listed below and the following Section 4.2 den otes which
standard is applicable for each assessment type:
• BRE Guide –3rd Edition of BR 209 BRE Site Layout Planning for Daylight and Sunlight
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 11
4.2 Reference Standards & Summary of Assessments Undertaken
The various daylight and sunlight assessments that were undertaken using the IES VE software
are based on a number of different standards which are referenced in the individual sections
of this report. For clarity, the assessments that were undertaken are summarised below as
well as the reference standards that were used for each (where applicable):
• Shadow Analysis
o Assessed using shadow images cast at key times throughout the year, i.e. March
21st, June 21st and December 21st to determine if any overshadowing impact occurs
and to what extent to any existing neighbouring dwellings in accordance with the
BRE Guide (3rd Edition).
• Sunlight to Amenity Spaces
o Assessed using annual Solar Exposure calculations to determine any impact to
existing amenities and the sunlight received and also to assess the proposed
developments amenity spaces to derive how much sunlight they can expect to
receive in accordance with the BRE Guide (3rd Edition).
• Sunlight to Existing Buildings
o Assessed using the Annual Probable Sunlight Hours (APSH) method in accordance
with the BRE Guide (3rd Edition) - to determine any impact to sunlight received to
the existing neighbouring building main living areas.
• Daylight to Existing Buildings
o Assessed using the Vertical Sky Component (VSC) method in accordance with the
BRE Guide (3rd Edition) - to determine any impact to existing daylight received to
the existing building neighbouring the site.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 12
4.3 Orientation
The model orientation has been taken from drawings provided by the Architect with the
resulting angle shown below used in the analysis.
Orientation
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 13
4.4 Proposed Model
The following images illustrate the models created from the architectural information
provided and the use of Google/Bing maps where information was absent.
Existing Situation Proposed Scheme View looking from North of Site View looking from East of Site View looking from South of Site View looking from West of Site RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 14
Proposed Model Images Estate Road View No. 30 Rear Garden View
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 15
4.5 Potential Sensitive Receptors
To help understand the potential impact to surrounding buildings , potential sensitive
receptors were identified as illustrated below.
Site Boundary
Neighbouring House North
30 Knockcarrick West RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 16
5 Shadow Analysis
The statistics of Met Eireann, the Irish Meteorological Service, show that the sunniest months
in Ireland are May and June, based on 1991-2020 averages or latest:
https://www.met.ie/climate/30-year-averages.
The following can also be shown:
• During December a mean daily duration of 1.7 hours of sunlight out of a potential 7.3
hours sunlight each day is received (i.e. only 23% of potential sunlight hours).
• During June a mean daily duration of 5.8 hours of sunlight out of a potential 15.9 hours
sunlight each day is received (i.e. only 36% of potential sunlight hours).
Therefore, the impacts caused by overshadowing are generally most noticeable during the
summer months and least noticeable during the winter months. According to the BRE (3rd
Edition) in Section 3.3.13:
“Where there are existing buildings as well as the proposed one, ‘before’ and ‘after’ shadow
plots showing the difference that the proposed building makes may be helpful. In interpreting
the impact of such differences, it must be borne in mind that nearly all structures will create
areas of new shadow, and some degree of transient overshadowing of a space is to be
expected.”
Section 3.3.14 states:
“If a space is used all year round, the equinox (21 March) is the best date for which to prepare
shadow plots as it gives an average level of shadowing”
In Section 3.3.15:
“As an optional addition, plots for summertime (for example 21 June) may be helpful as they
will show the reduced shadowing then, although it should be borne in mind that 21 June
represents the best case of minimum shadow, and that shadows for the rest of the year will
be longer. Conversely if winter shadows (e.g. 21 December) are plotted, even low buildings
will cast long shadows.”
Based on the above, and for completeness, this section will consider the shadows cast by the
proposed development on the following dates:
• March 21st / September 21st (Equinox)
• June 21st (Summer Solstice)
• December 21st (Winter Solstice) RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 17
These images illustrate shadows cast for ‘perfect sunny’ conditions with no clouds and
assumed that the sun is shining for every hour shown. Given the discussion above it is
important to remember that this is not always going to be the case.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 18
5.1 Plan View
5.1.1 March 21st
Existing Proposed March 21st - 8:00 March 21st - 10:00 March 21st - 12:00 RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 19
Existing Proposed March 21st - 14:00 March 21st - 16:00 March 21st - 18:00
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 20
5.1.2 June 21st
Existing Proposed June 21st - 8:00 June 21st - 10:00 June 21st - 12:00 RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 21
Existing Proposed June 21st - 14:00 June 21st - 16:00 June 21st - 18:00 RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 22
Existing Proposed June 21st - 20:00
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 23
5.1.3 December 21st
Existing Proposed December 21st - 8:00 December 21st - 10:00 December 21st - 12:00 RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 24
Existing Proposed December 21st - 14:00 December 21st - 16:00
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 25
5.2 3D View
5.2.1 March 21st
Existing Proposed March 21st - 8:00 March 21st - 10:00 March 21st - 12:00 March 21st - 14:00 RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 26
Existing Proposed March 21st - 16:00 March 21st - 18:00
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 27
5.2.2 June 21st
Existing Proposed June 21st - 8:00 June 21st - 10:00 June 21st - 12:00 June 21st - 14:00 RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 28
Existing Proposed June 21st - 16:00 June 21st - 18:00 June 21st - 20:00
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 29
5.2.3 December 21st
Existing Proposed December 21st - 8:00 December 21st - 10:00 December 21st - 12:00 December 21st - 14:00 RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 30
Existing Proposed December 21st - 16:00 RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 31
5.3 Discussion
The shadow analysis illustrates different shadows being cast at key times of the year (March
21st, June 21st and December 21st) for the Existing Situation and the Proposed Scheme. The
results from the study are summarised as follows:
Neighbouring House – North
Minor additional shading noted in December* (1000-1200). No additional shading noted at
any other period.
30 Knockcarrick - West
Minor additional noted in the Morning of March and June 0800. No additional shading
noted at any other period.
* Overshadowing can be expected in December when the sun is lower in the sky and shadows
cast are much longer. Although this is the case, overshadowing is least noticeable during the
winter months as there is a lot less sunlight available at this time of ye ar and so the overall
impact is vastly reduced.
The potential shading impact is quantified via the “Sunlight to Amenity Spaces” and “Daylight
to Existing Buildings” section of this report. RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 32
6 Sunlight to Amenity Spaces
6.1 Guidance Requirements
The impact of the proposed development on the sunlight availability to the amenity spaces
will be considered to determine how the amenity spaces perform when assessed against the
BRE Guide (3rd Edition) which states the following in Section 3.3.17:
The BRE Guide (3rd Edition) states that for a space to appear adequately sunlit throughout the
year, at least half of a garden or amenity space should receive at least 2 hours of sunlight on
March 21st. In the case of existing amenity spaces, if they are already below the 50% threshold
then the BRE recommends the results kept to within 80% of the existing situation.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 33
6.2 Amenity Spaces
This analysis will be performed on the amenity spaces illustrated in the image below.
Amenity Spaces
Existing Gardens
The following images illustrate the predicted results with respect to this space receiving at
least 2 hours of sunlight on March 21st. Any areas that receive less than 2 hours of sunlight
are colour-coded in grey.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 34
6.2.1 Existing Amenity Spaces
As stated above for a space to appear adequately sunlit throughout the year, at least half of
a garden or amenity area should receive at least 2 hours of sunlight on March 21st. In the case
of existing amenity spaces, if they are already below the 50% threshold then the BRE
recommends the results kept to within 80% of the existing situation with the proposed
development in place.
This analysis performed on the following amenity spaces highlighted below:
Existing Amenity Spaces
Existing Amenity
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 35
6.2.1.1 Existing Amenity Area Results
Existing Situation: Absolute Scale Showing all Hours of Sunlight Received
Proposed Situation: Absolute Scale Showing all Hours of Sunlight Received
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 36
Existing Situation: Hours of Sunlight > 2 Illustrated in Red
Receives more
than 2 hours of
sunlight
Receives less
than 2 hours of
sunlight
Proposed Situation: Hours of Sunlight > 2 Illustrated in Red
Receives more
than 2 hours of
sunlight
Receives less
than 2 hours of
sunlight
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 37
6.2.1.2 Existing Amenity Results
Existing Amenity Results
Ref Area
(m2)
Existing Area
>2 hrs
Existing Area with
Proposed
Development in Place
>2 hrs
Proposed vs
Existing
(%)
Comment
(m2) (%) (m2) (%)
1 213 194 91% 194 91% 100% ✓
2 124 79 64% 79 64% 100% ✓
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 38
6.3 Discussion
As outlined in Section 3.3.17 of the BRE Guide (3rd Edition), for a space to appear adequately
sunlit throughout the year, at least half of the garden or amenity area should receive at least
2 hours of sunlight on March 21st. In the case of Existing amenity spaces, if they are already
below the 50% threshold then the BRE recommends the results kept to within 80% of the
existing situation.
Existing Amenity Spaces
On March 21st, all of the existing neighbouring amenity spaces tested will receive the same
levels of sunlight with the proposed development in place when compared to the existing
scenario. All the amenity spaces tested complying with the recommendations in the BRE
Guide outlined above and highlight a negligible impact to neighbour’s sunlight received
throughout the year.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 39
7 Sunlight to Existing Buildings
7.1 Guidance – BRE Guide (3rd Edition)
The BRE Guide (3rd Edition) states that interiors where the occupants expect sunlight should
receive at least one quarter (25%) of annual probable sunlight hours, including at least 5% of
annual probable sunlight hours during the winter months, between 21 st September and 21st
March.
Here 'probable sunlight hours' means the total number of hours in the year that the sun is
expected to shine on unobstructed ground, allowing for average levels of cloudiness for the
location in question.
If a window reference point can receive more than 25% of annual probable sunlight hours,
including at least 5% of annual probable sunlight hours during the winter months between
21st September and 21st March, then the room should still receive enough sunlight. Any
reduction in sunlight access below this level should be kept to a minimum .
If the available sunlight hours are both less than the amount given and less than 0.8 times
their former value, either over the whole year or just during the winter months (21 st
September to 21st March) and reduction in sunlight across the year has a greater reduction
than 4%, then the occupants of the existing building will notice the loss of sunlight.
BRE 3rd Edition guidance document Site Layout Planning for Daylight and Sunlight
As such this study will compare the Existing Scheme and Proposed Schemes and consider if
the values on the existing buildings meet the requirements outlined above when compared
to their former value (that of the Existing scheme).
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 40
7.2 APSH Exclusions
The BRE recommendations note that if a new development sits within 90 ° of due south of any
main living room window of an existing dwelling, then these should be assessed for APSH.
However, there are several exceptional cases in which APSH is not required to be calculated,
as indicated below:
BRE 3rd Edition guidance document Site Layout Planning for Daylight and Sunlight
Consequently, APSH will only be calculated for adjacent windows which meet the following
conditions:
1. The height distance rule it not met and the existing building has living room with a
main window which faces within 90 degrees of due south with the 25 ° rule not being
met either.
2. Existing building is located to the North, East, or West of the Proposed Development.
3. The existing main living room window lies within 20 degrees of due south and has a
VSC of less than 27%.
Based on the criteria outlined above, only the existing dwellings at Beaumont Grove and part
of the Ellenfield Road residences were included within the APSH assessment. RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 41
7.3 APSH Assessment
Based on the above criteria, the locations in the following sections have been modelled and
analysed with the results also included.
Please note, the “Comment” symbol in each of the tables represents the following:
✓/✓ For these locations, both the Proposed Scheme annual and winter APSH results are
greater than 25% and 5% respectively, or are greater than 0.8 times their former value
or are less than 4% overall annual loss with the proposed development in place.
✓/ x For these locations, the annual APSH results are greater than 25% or are greater than
0.8 times their former value with the proposed development in place, however, the
winter results are below recommendations.
x /✓ For these locations, the annual APSH results are less than the recommended values,
however, the winter APSH results are greater than 5% or greater than 0.8 times their
former value with the proposed development in place.
x / x For these locations, both the annual and winter APSH results are less than 25% and
5% respectively, and less than 0.8 times their former value or are greater than 4%
overall annual loss with the proposed development in place.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 42
7.3.1 Knockcarrick House – North
Points
Existing Situation
APSH
Proposed Scheme
APSH
Proposed APSH as a % of
Existing Situation Comment
Annual Winter Annual Winter Annual Winter
1 59.8 24.9 58.0 23.0 97% 92% ✓/✓
2 60.8 25.8 59.4 24.4 98% 95% ✓/✓
3 56.8 21.8 55.8 20.9 98% 96% ✓/✓
RECEIVED: 30/07/2026
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Daylight, Sunlight and Overshadowing Study
Page | 43
7.4 Discussion
This study considers the proposed scheme and tests if the Annual Probable Sunlight Hours
(APSH) results for the living room windows (existing properties) are greater than 25% annual
and 5% winter sunlight or are greater than 0.8 times their former value with the proposed
development in place or the reduction in sunlight across the year is less than 4% with the
proposed development in place.
When compared to the Existing Scheme, 100% of the tested points (3 no.) meet the BRE
recommended values. These results highlight that the proposed development will have
negligible impact to the sunlight received to these existing neighbouring properties.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 44
8 Daylight to Existing Buildings
8.1 Guidance – BRE Guide (3rd Edition) / IS/BS EN 17037-2018+A1 2021
When designing a new development, it is important to safeguard the daylight to nearby
buildings. The BRE Guide provides numerical values that are purely advisory. Different criteria
may be used based on the requirements for daylighting in an area viewed ag ainst other site
layout constraints. Another issue is whether the Existing building is itself a good neighbour,
standing a reasonable distance from the boundary and taking no more than its fair share of
light. Any reduction in the total amount of skylight can be calculated by determining the
vertical sky component at the centre of key reference points. The vertical sky component
definition from the BRE Guide (3rd Edition) is described below:
The maximum possible VSC value for an opening in a vertical wall, assuming no obstructions,
is 40%. This VSC at any given point can be tested in RadianceIES, a module of IES VE.
For typical residential schemes the BRE Guide (3nd Edition) states the following in Section
2.2.7:
As such this study will compare the Existing scheme and Proposed scheme and consider if the
values on the Existing buildings are above 27% or not less than 0.8 times their former value
(that of the Existing scheme).
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 45
It is also important to note that Section 2.1.6 of the BRE Guide states that if the VSC is between
15% and 27%, special measures such as larger windows can provide adequate daylight (refer
to extract below).
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 46
8.2 Assessment - 25-Degree Rule
Section 2.2.5 of the BRE Guide states that if in a section perpendicular to the window wall, no
angle subtended more than 25 degrees, as shown in the image below, it is not necessary to
do a full calculation as the daylight impact will be unnoticeable to t he occupants. The
following screenshots show the section images produced as evidence for each of the
qualifying views for the 25-degree rule.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 47
8.3 Assessment
Based on the above criteria, the locations in the following sections have been modelled and
analysed with the results also included.
Please note, the “Comment” symbol in each of the tables represents the following:
✓ For these locations, the Proposed Scheme VSC value is greater than 27% or 0.8 times
their former value (that of the Existing Situation/Permitted Scheme).
✓1 For these locations, the Proposed Scheme VSC value is less than 0.8 times its former
value (that of the Existing). However, the Proposed Scheme VSC values are between
15% and 27% and hence adequate daylight should still be expected (as per Section
2.1.6 of the BRE Guide) given the presence of larger than conventional windows.
x For these locations, the Proposed Scheme VSC value is less than 15% and less than 0.8
times its former value (that of the Existing Situation), therefore, it does not achieve
the BRE recommendations.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 48
8.3.1 30 Knockcarrick - West
Ref. Existing Situation Proposed Scheme
VSC
Proposed VSC as a % of
Existing Situation Comment
1 38.0 38.1 100% ✓
2 38.3 38.4 100% ✓
3 36.7 36.6 100% ✓
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 49
8.3.2 Knockcarrick House – North
Ref. Existing Situation Proposed Scheme
VSC
Proposed VSC as a % of
Existing Situation Comment
1 37.6 37.1 99% ✓
2 37.8 37.4 99% ✓
3 36.1 35.7 99% ✓
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 50
8.4 Discussion
This study considers the Proposed Scheme and tests if the VSC results are greater than 27%
or not less than 0.8 times the value of the Existing Situation.
When compared to the Existing Situation, of the 6 no. points tested, 100% have a Proposed
VSC value greater than 27% or not less than 0.8 times their former value compared to the
Existing Situation, thus complying with the BRE Guidelines. The results highlight a negligible
impact to the neighbours where daylight is concerned.
RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 51
9 Conclusion
The following can be concluded based on the assessments undertaken:
9.1 Shadow Analysis
The shadow analysis illustrates different shadows being cast at key times of the year (March
21st, June 21st and December 21st) for the Existing Situation and the Proposed Scheme. The
results from the study are summarised as follows:
Neighbouring House – North
Minor additional shading noted in December* (1000-1200). No additional shading noted at
any other period.
30 Knockcarrick - West
Minor additional noted in the Morning of March and June 0800. No additional shading
noted at any other period.
* Overshadowing can be expected in December when the sun is lower in the sky and shadows
cast are much longer. Although this is the case, overshadowing is least noticeable during the
winter months as there is a lot less sunlight available at this time of ye ar and so the overall
impact is vastly reduced.
The potential shading impact is quantified via the “Sunlight to Amenity Spaces” and “Daylight
to Existing Buildings” section of this report.
9.2 Sunlight to Amenity Spaces
As outlined in Section 3.3.17 of the BRE Guide (3rd Edition), for a space to appear adequately
sunlit throughout the year, at least half of the garden or amenity area should receive at least
2 hours of sunlight on March 21st. In the case of Existing amenity spaces, if they are already
below the 50% threshold then the BRE recommends the results kept to within 80% of the
existing situation.
Existing Amenity Spaces
On March 21st, all of the existing neighbouring amenity spaces tested will receive the same
levels of sunlight with the proposed development in place when compared to the existing
scenario. All the amenity spaces tested complying with the recommendations in the BRE
Guide outlined above and highlight a negligible impact to neighbour’s sunlight received
throughout the year.
9.3 Sunlight to Existing Buildings
This study considers the proposed scheme and tests if the Annual Probable Sunlight Hours
(APSH) results for the living room windows (existing properties) are greater than 25% annual RECEIVED: 30/07/2026
Knockcarrick, Monaghan
Daylight, Sunlight and Overshadowing Study
Page | 52
and 5% winter sunlight or are greater than 0.8 times their former value with the proposed
development in place or the reduction in sunlight across the year is less than 4% with the
proposed development in place.
When compared to the Existing Scheme, 100% of the tested points (3 no.) meet the BRE
recommended values. These results highlight that the proposed development will have
negligible impact to the sunlight received to these existing neighbouring properties.
9.4 Daylight to Existing Buildings
This study considers the Proposed Scheme and tests if the VSC results are greater than 27%
or not less than 0.8 times the value of the Existing Situation.
When compared to the Existing Situation, o f the 6 no. points tested, 100% have a Proposed
VSC value greater than 27% or not less than 0.8 times their former value compared to the
Existing Situation, thus complying with the BRE Guidelines. The results highlight a negligible
impact to the neighbours where daylight is concerned.
9.5 Observations
It is important to note that the recommendations within the BRE Guide (3 rd Edition) itself
states “although it gives numerical guidelines these should be interpreted flexibly because
natural lighting is only one of many factors in site layout design”, Although this is true
appropriate and reasonable regard has still been taken to the BRE guide.
Whilst the results shown relate to the criteria as laid out in the BRE Guide (3rd Edition), it is
important to note that the BRE targets are guidance only and should therefore be used with
flexibility and caution when dealing with different types of sites.
In addition, BRE Guide 3rd Edition also notes:
“This report is a comprehensive revision of the 2011 edition of Site layout planning for
daylight and sunlight: a guide to good practice. It is purely advisory and the numerical target
values within it may be varied to meet the needs of the development and its location.”
Taking all of the above information into account and based on the results from each of the
assessments undertaken, the proposed development performs well when compared to the
recommendations in the BRE Guide 3rd Edition when considering the potential impacts to the
existing neighbouring properties. Overall, there will be a negligible impact to the neighbours
when considering sunlight and daylight if the proposed development is built. RECEIVED: 30/07/2026