Light,Lighting and Wellbeing in Buildings by Monisha Selvaraju

MONISHA SELVARAJU KTKZ5 BENV0030 Light,Lighting and Wellbeing in Buildings Healthy lighting for classrooms Dr Stephen Cannon-Brookes

11/04/2021 2999

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Healthy Lighting for Classroom In Chennai, India

MONISHA SELVARAJU

11/04/2021

BENV0030

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TABLE OF CONTENTS Nomenclature & Glossary ................................................................................................................. 3 Executive summary .......................................................................................................................... 4 1

Review of current recommendations & lighting brief .................................................................. 5 1.1

Background ........................................................................................................................ 5

1.2

Effect of lighting on health, wellbeing and comfort on school children ................................. 5

1.2.1

Visual comfort .............................................................................................................. 5

1.2.2

Vitamin D ..................................................................................................................... 5

1.2.3

Circadian Rhythms ...................................................................................................... 5

1.2.4

SADs and Therapeutic effects ..................................................................................... 5

1.3

PROJECT BRIEF - Indoor lighting in a classroom located in Chennai, India ...................... 6

1.4

Lighting design challenges in a classroom .......................................................................... 6

1.4.1

Adequacy .................................................................................................................... 6

1.4.2

Building coherence ...................................................................................................... 7

1.4.3

Visual comfort .............................................................................................................. 7

1.4.4

Information .................................................................................................................. 7

1.4.5

Statutory, good practice ............................................................................................... 7

1.5 2

Review of current healthy lighting standards ....................................................................... 7

Initial daylighting analysis ........................................................................................................ 11 2.1

NO – SKY- LINE ............................................................................................................... 11

2.2

LIMITED ROOM DEPTH INDEX....................................................................................... 12

2.3

AVERAGE DAYLIGHT FACTOR ...................................................................................... 13

2.4

SUN PATH AND SOLAR PENETRATIONS ..................................................................... 14

Results .................................................................................................................................... 17 3

Dynamic daylight modelling and metrics .................................................................................. 18

An electric lighting strategy ...................................................................................................... 21

Summary of findings and review .............................................................................................. 23

References ..................................................................................................................................... 25 Appendix......................................................................................................................................... 27

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NOMENCLATURE & GLOSSARY ASHRAE- American society of Heating IGBC – Indian Green Building Council ISHRAE- The Indian Society of Heating, Refrigerating and Air Conditioning Engineers ECBC- The Energy Conservation Building Code, was developed by the Govt. of India for new commercial buildings and released on 27th May 2007. EFA – Education funding agency LEED–INDIA – Leadership in Energy and Environmental Design (LEED-INDIA) Green Building Rating System is a recognized point of reference both in our country as well as worldwide for the design, construction and further, operation of high-performance green buildings. IS:7492-1976 - Indian Standard code for daylighting in educational buildings IS 3646 (Part 1): 1992 – Indian standard code for daylighting in interior spaces. NLC- National Lighting Code of India Lumens - Total quantity of visible light emitted by a source per unit volume of time. Candela- The base unit of luminous intensity in SI i.e., luminous power per unit solid angle emitted by a point light source in a particular direction (cd) Illuminance - Illuminance is the total luminous flux incident on a surface, per unit area. (lux or lumens per square meter) Luminance - Luminance is a photometric measure of the luminous intensity per unit area of light travelling in given direction (cd/m2) Luminous efficacy - is a measure of how well a light source produces visible light. (lumens/W) aVD- Average daylight factor sDA-Spatial daylight autonomy UDI- Useful daylight Illumination ASE- Annual Sunlight exposure

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EXECUTIVE SUMMARY Lighting in a classroom has several health benefits, this report evaluates the multiple aspects of healthy lighting standards for a sample classroom in Chennai, India by creating a suitable brief with current metrics. An initial daylighting analysis is performed to find the most suitable classroom orientation with a solar protractor. It is further tested using a CBDM tool “Dynamic Daylighting". Several iterations with different parameters are simulated to get an optimized classroom that suits the brief's requirement. This is further integrated with artificial lighting to befit the brief. Subsequently, lighting conflicts, current trends, and practices in India are investigated.

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1 REVIEW OF CURRENT RECOMMENDATIONS & LIGHTING BRIEF 1.1

BACKGROUND

Classroom environment affects student learning performance, they further enable in developing clear learning goals, relevant content, and building social skills & strategies to aid the student to succeed (Weimer, 2009). Lighting is one of the primary parameters affecting classroom and student’s learning potential. Light is a part of electromagnetic spectrum which has wavelength of 400-700 nanometer(nm), called visible spectrum. In a building lighting system can be segregated into 2 categories,1) Daylighting, 2) Artificial Lighting.

1.2 1.2.1

EFFECT OF LIGHTING ON HEALTH, WELLBEING AND COMFORT ON SCHOOL CHILDREN Visual comfort

The primary purpose of lighting is to provide illumination for the performance of a ‘visual task with maximum speed, accuracy, ease and comfort, and a minimum strain and fatigue’(Kisan and Sangathan, 1987).Adequate lighting is necessary for a classroom environment for visual task performance as well to ensure safety and reduce the risk of falls and injuries. Teaching spaces in schools cater to a wide spectrum of activities and students involving several age groups. The eye of children is in its formative stage in the lowest age groups, and since vision is aided by memory and memory relates to objects seen, a higher level of lighting is required to identify the objects (Standards, 1976). 1.2.2

Vitamin D

Solar radiation is necessary for our psychological and physiological wellbeing. (Walrand, 2021) reveals that the recent COVID-19 pandemic affects people with lower concentrations of vitamin D. Moreover, Vitamin D is responsible for causing rickets, mood swings, bone-related diseases, etc. Studies show that daylighting (UV rays from the sun) helps in vitamin D synthesis (Hobday, 2008). Similarly, excessive direct sunlight and radiation is harmful to body. 1.2.3

Circadian Rhythms

Light affects our circadian rhythms, a 24-hour biological clock within the body that regulates darkness and light which is responsible for sleep, hunger, regulate body temperature, alertness, and hormone secretion like melatonin. The pineal gland produces melatonin in a 24-hour cycle based on the amount of light received, thus regulating the body’s circadian rhythm(Neubauer, 2001). The hormone is at its peak during the night and helps with healthy sleep, whereas lowest during daylight thereby contributing to alertness. Disturbances in these cyclic rhythms occur due to improper daylight exposure and excessive exposure to bright light in the night leading to improper exposure to light which eventually affects health (van Bommel and van den Beld, 2004). 1.2.4

SADs and Therapeutic effects

Seasonal affective disorder (SADs) which predominantly occurs in latitudes above 50 degrees, and other types of depression can be effectively reduced by both artificial and natural light therapy, they tend to disappear in brighter seasons (Fotios, 2015).Sunlight played a pivotal role in infection control and prevention of diseases in buildings before the discovery of antibiotics (Hobday, 1997).

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1.3

PROJECT BRIEF - INDOOR LIGHTING IN A CLASSROOM LOCATED IN CHENNAI, INDIA

Overall Aim The lighting design for a school classroom located in Chennai, India 13.0827° N, 80.2707° E with latitude and longitude. Section 1.4 & 1.5 are considered for designing an indoor lighting design. Chennai has a warm humid climate with the plan and section of the classroom is attached fig 1.3 for reference and further working. The brief aims at developing a healthy lighting design outcome through initial lighting analysis and an extended lighting analysis using daylight simulation software (Andrew marsh) and CBDM simulation results. It is further compared to the healthy lighting design metrics as laid out in this brief to further re-evaluate the design with an electric lighting strategy. The design tries to overcome the lighting challenges. The brief sets out targets for the sample classroom located in Chennai, below into two parts namely, 1) Daylighting and view targets and 2) Artificial Lighting targets.

Figure 1.3 Sample Classroom located in Chennai, India.

1.4

LIGHTING DESIGN CHALLENGES IN A CLASSROOM

The lighting brief tries to address the 5 parameters mentioned below as a guideline for creating a well-lit interior space (Cannon-brookes, 2019) 1.4.1

Adequacy

(Heschong, Wright and Okura, 2002)shows students exposed to natural light achieved scores 18% higher than students exposed to minimal light. Moreover, natural daylight proves to have many health benefits and affects students learning and wellbeing.

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1.4.2

Building coherence

Thermal comfort, Acoustics, and Indoor air quality along with lighting are integrated elements that play a crucial part in classroom design. Window area, Fenestration, building form, interior finishes play a significant role in defining the optimum lighting. ‘In India, especially in latitudes less than 23” N such incursion is inevitable for any orientation and suitable overhangs for east, south, and west oriented apertures will have to be provided. There is also an increase in internal daylight from design time to noon (there is a decrease thereafter) which tends to make interiors brighten up considerably’ (Standards, 1976). 1.4.3

Visual comfort

Visual discomfort is caused when there is excessive direct or indirect light that causes glare. Furthermore, flicker, maintenance of the room and lighting equipment, glare affect classroom wellbeing. Flicker causes epilepsy, whereas glare hinders the visual task resulting in headaches, poor concentration levels, and decreased productivity. (Young, 2014) shows that classrooms with unnecessary fluorescent lighting causes headaches and impair visual performance. (Harle, Shepherd and Evans, 2006)further showed that patterns are a source of discomfort glare that led to visual stress by causing headaches. 1.4.4

Information

Provision of widows or glazing provides outdoor configurations. They give a sense of belonging and place. Viewing nature (Biophilia) helps in improving student’s performance and mood (Müeller, 2013). 1.4.5

Statutory, good practice

The main criteria followed for classroom design are the National lighting code of India (Kisan and Sangathan, 2010)(NLC), IS 7942 – 1976 (Indian Standard code for daylighting in educational buildings), IGBC (Indian Green Building Council), ECBC (The Energy Conservation Building Code) LEED- India and WELL v4.

1.5

REVIEW OF CURRENT HEALTHY LIGHTING STANDARDS

Daylighting IS 7942 – 1976 which is the Indian Standard code for daylighting in educational buildings quotes "Its primary aim is to provide sufficient illumination for school children for visual task performance as well as to eliminate stress and strain as they are young and use their eyes to observe and learn the surrounding environment. Excess light impairs the eye’s cones ", like CIBSE TM 57 in the UK. The design overcast sky in Chennai is considered as 7000cd/sqm or 7000 lux (Subramanian and Kamalesvari, 2016). Since the metrics in India as per table 1.5 vary from 1.9 to 3.8 %, the desirable daylight illuminance required for the same will be ranging from 133 Lux to 266 Lux (under an overcast sky of 7000 lux). For the design objective, we can confine DF higher than 2.75%. Nevertheless, most standards and IES handbook suggest an illumination of 300 lux as a standard metric. But when it comes to healthy lighting (Cajochen and Wirz-justice, 1996) suggest that a colour temperature of 4000 K & 100lux illumination at the eye level is the transition point between low and high subjective alertness. Further, it was concluded that 70 -120 lux at eye

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level is when sleep to alert transmission occurs. Thus, an integrated lighting strategy is preferred in brief with an emphasis on daylighting (Table 1.5a,1.5c,1.5d) Table 1.5 a Daylighting & view targets to be adopted for Classroom in Chennai, India Parameter / Metrics Daylight Factor (DF)

Working plane

Orientation

Target Descriptions According to Indian Standard code for daylighting in educational buildings a daylight factor of 1.9 to 3.8 % is recommended in classrooms.

Source IS: 7942 - 1976

Whereas IGBC prescribes a Daylight factor of 2.5% in green rated school buildings. However, we will ensure to have a target of DF > 2.75% ‘In educational buildings it may vary from 0.60 to 0.90 m depending on the age of students and type of task carried out’. Working plane considered here is 700mm Building to the preferably oriented along the longer axis facing the North -South direction, sufficient and suitable shading to be done in the east and west side.

(Green and Council, 2013)

Interior wall finishes

(Standards, 1976)

(Subramanian and Kamalesvari, 2016) (Standards, 1976)

‘Interior of the room possesses the following reflection factors. a) Walls: 45-50 percent, b) Ceiling: 70-75 percent, and c) Floor: 25-30 percent. • Ceiling height is taken to be 2.75 m. • Windows are provided with louvers to cut the incursion of sunlight. • Combined thickness of wall and width of louver is taken to be 60 cm. • Ground reflection factor is taken as 0.25; and • No external obstruction’. Illumination

Views

Since daylight Factor is useful only for overcast skies (cloudy sky), it is only useful for certain period, Thus ‘Illuminance is the total luminous flux incident on a surface, per unit area. (lux or lumens per square meter) A minimum of 150 to 300 lux is required for classrooms. In India’ ‘Achieve direct line of sight to vision glazing between 0.9 meters (3 feet) and 2.1 meters (7 feet) above the finished floor level, for building occupants in at least 75% of all regularly occupied spaces. Also, the project shall comply with the following criteria: • The building occupants must not have any obstruction of views at least 8 meters (26.2 feet) from the exterior vision glazing. or • The building occupants must have access either to sky or flora & fauna or both’.

NBC 2016 National Building code of India (Kisan and Sangathan, 2010) & IS: 7942 - 1976 IGBC (Green and Council, 2013)

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Annual Daylight Metrics ‘UDI is defined as the annual occurrence of illuminances across the work-plane that is within a range considered ‘useful’ by occupants. This is subdivided: UDI- acceptable in India 75% of the regularly occupied spaces with daylight illuminance levels for a minimum of 110 Lux (and a maximum of 2,200 Lux) in a clear sky condition on 21st September at 12 noon, at working plane (through simulation or measurement approach) Areas with 2,200 Lux or more daylight illumination levels should not be considered’.

IGBC

UDI-s

Supplementary Light as low as possible, restricted to <30 % for the purpose of brief.

UDI-e

Excessive light as low as possible, restricted to 5 % to avoid glare and for the purpose of brief.

(Education Funding Agency (EFA), 2014) (Education Funding Agency (EFA), 2014)

Useful daylight Illuminance (UDI) User defined

Spatial Design Autonomy (sDA)

Annual Sunlight Exposure (ASE)

Preferred: sDA300/50% > 75% on occupied area Acceptable: sDA300/50% > 55% on occupied area Space averaged over a grid of points, Hourly sky luminance conditions Preferred: ASE1000/250h < 3% on occupied area Acceptable: ASE1000/250h < 7% on occupied area Sufficient: ASE1000/250h < 10% on occupied area Space average over a grid of points, Hourly sky illuminance conditions

(Nabil and Mardaljevic, 2005)

WELL

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Table 1.5b Metrics definitions Useful daylight Illuminance (UDI)

‘UDI is defined as the annual occurrence of illuminances across the work-plane that is within a range considered ‘useful’ by occupants. This is subdivided:

(Education Funding Agency (EFA), 2014)

• UDI-a (x to y lux) where daylight is acceptable and electric lighting would not be needed for most of the day; achieving a high UDI-a percentage signifies the space is predominantly daylit throughout and glare is controlled • UDI-e (above y lux) where the amount of daylight would be considered excessive, and a source of glare and the blinds would need to be operated • UDI-s (below x lux) where the light would be considered insufficient without electric lighting the output specification sets a minimum target of an average of 80% UDI-a for each learning space, sports hall, and exam area’. However, UDI a is considered as 110 to 2200 lux and 75 % in India and for the sample classroom. Spatial Design Autonomy (sDA)

Annual Sunlight Exposure (ASE)

‘is the annual sufficiency of daylight levels in a space. sDA examines the percentage of an analysis area (eg. Working plane) that meets a minimum illuminance level (e.g. 300 lux) for a specified fraction of the operating hours per year (e.g. 50% of the operational hours of the year)’

IES

‘Describes the annual potential for visual discomfort in a space. ASE is the percentage of an analysis working plane area that exceeds a specified illuminance level more than a specified number of hours’.

IES

Artificial Lighting For a high visual performance an illuminances of 1000 to 6000 lux are recommended (Lange, 2002).However, Illuminances of more than 1000 lux on the retina for more than one hour are necessary to trigger the circadian response appropriately (Müeller, 2013). ‘The Colour Rendering Index (CRI) is a scale from 0 to 100 percent indicating how accurate a "given" light source is at rendering colour when compared to a "reference" light source, such a sun’. (Cajochen and Wirz-justice, 1996). Refer table 1.5.c and 1.5.d for artificial daylight metrics and parameters.

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Table 1.5c Luminance based metrics for Healthy Artificial lighting in a classroom in Chennai. Parameter Colour rendering Index. CRI

Description 55 is Warm Light 55 – 60 – Cool White 60 – 100 – Daylight

Glare Index

1% in classrooms, ‘also to minimise glare the angle between the sight from the student to the farthest window edge and the normal to the desk length is within 50”’.

IS: 7942 - 1976

Circadian Metrics

‘Early education, primary and secondary schools, and adult education for students primarily under 25 years of age: Light models (which may incorporate daylight) show that at least 125 equivalent melanopic lux is present at 75% or more of desks, on the vertical plane facing forward 1.2 m [4 ft] above finished floor (to simulate the view of the occupant). This light level is present for at least 4 hours per day for every day of the year’. Maximizing daylight and integrating daylight with dimmer controls. Occupancy sensors are recommended in the toilets. Preferred Artificial source of lighting are CFL, T-5 lamps, LED.

WELL Part 4-Melanopic Light Intensity in Learning Areas

Artificial Lights

Source IGBC/ LEED (Green and Council, 2013)

< 55 - Poor. 60 – 55 – Good 90 – 100 – Excellent

ECBC ASHRAE

Table 1.5d Luminance based metrics for Healthy Artificial lighting in a classroom, Types of Lamps

Luminous Efficacy

CRI

Working Hours

CFL

40-75

8000-20000

Fluorescent (T5)

73-114

70-90

10000-45000

LED

200-280

70-90

15000-50000

2 INITIAL DAYLIGHTING ANALYSIS 2.1

NO – SKY- LINE Table 2.1 Definitions

Term Working plane No skyline

Definition ‘IS: 7942 – 1976 defines Working Plane as ‘the plane (real or imaginary) at which work is usually done and therefore on which illumination is specified and measured. Unless otherwise indicated it is assumed to be horizontal at a height 0.85 m.’ ‘No skyline indicates when the Sky Component is zero. Any light received on surface interior to the line will be the recipients of only externally and internally reflected daylight’.

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Daylight in an interior will appear uneven if a significant part of the interior is beyond the No-Skyline. In the figure 2.1 the no sky-line point is beyond the classroom’s west wall, thus it means that the interior surface receives daylight. This is due to the longer distance of obstruction structure i.e., 15m apart from the classroom. IS: 7942 – 1976 section 6.6 refers to the role of External obstructions, thus it can be inferred the closer the obstruction the lesser the daylight factor and vice versa.

Figure 2.1 No Skyline of sample classroom in Chennai

2.2

LIMITED ROOM DEPTH INDEX

‘A side lit room will appear evenly lit if its depth (distance of the rear wall to the window) is less than a sum based on the height of the window, the width of the space and the reflectance of the rear of the room’ (Cannon-Brookes, 2021).

Figure 2.2 Limited Room depth Index

Source (Cannon-Brookes, 2021)

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Limiting Room Depth Index = where Rb is the area weighted average reflectance of the rear half of the room - typically 0.5 in offices. Here, Length (L) = 8m; Width (W) = 9m, Height (H) = 2.9m (Window height of 2.3 + sill height of 0.6m) Thus, 8

2 x 9 x 2.9 (9+2.9) x (1-0.5)

52.2 = 8.773 5.95

Since the value is not lesser or equal to the length, it can be inferred as the classroom not uniformly distributing light. Thus, it orders to obtain a uniform distribution, the window breadth needs to be wide.

2.3

AVERAGE DAYLIGHT FACTOR

Table 2.3.1 Daylight factor metrics – Source IES Handbook Daylight Factor (DF)

0-2% 2-5% >5%

Description ‘Daylight factor can be defined as is the ratio of the illuminance at a point on a plane in a room due to the light received from a sky of assumed or known luminance distribution, to that on a horizontal plane due to an unobstructed hemisphere of this sky. DF is calculated using’ Overcast sky, to eliminate the direct sunlight. The design overcast sky in Chennai is considered as 7000cd/sqm or 7000 lux (where 1 footcandle/sqft = 10.76391 lux) (Subracmanian and Kamalesvari, 2016). ‘space is inadequately light and so electric lighting is required’. ‘space is adequately light, but electric lighting may be required during some of the time’. ‘is well-lit space and electric lighting is not required during the daylight time. Glare may be a concern’.

Figure 2.3 Sectional view of model building and obstruction with solar penetrations passing through the projections and roof lines inside the window opening. Source: (Cannon-Brookes, 2021)

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Thus, Average Daylight factor formula is given below,

Were, W: Window area (m2); A: Area of all surfaces (m2); T: Glass transmittance including dirt. Ø: Visible sky angle (degrees); R: Average reflectance of the room surfaces Table 2.3.2 Daylight factor calculation Window Area (W)

Area of all surfaces (A)

Glass transmittance including dirt (T)

Visible sky angle (Ø)

Average reflectance of room surfaces (R)

There are 3 windows in the classroom, thus,

Sum of Area of

Double glazing is used for effective solar radiation as well for acoustical purpose, Thus, transmittance of 0.7 and a dirt transmittance factor of 0.67(Ghosh and Neogi, 2017), Thus window transmittance =

Calculated from Andrew marsh.com for Chennai location, the visible angle is 67.82

Average values of

3 x (1.6 x 2.3) m

Floor

Ceiling

North

South

East

15.96

=11.04 sq m

Ceiling

0.7

Wall

0.425

Floor

0.3

Total

0.475

0.67 x 0.7 = 0.469 West

Total

234.96

In Chennai, India the classrooms have White ceiling, Off white walls, and Terrazzo floorings. These materials reflectance’s are noted and averaged above.

On calculating DF for our sample classroom, Av DF = 11.04 x 0.469 x 67.82 234.96 (1 - 0.0475)

= 351.155

= 1.99 %

176.366

This value is below our target set of 2.75 to 3.8 %.

2.4

SUN PATH AND SOLAR PENETRATIONS

The following steps are involved in calculating sun path diagram for Chennai 13 N.

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Step 1 The angle suspended from the obstruction roof like to class window wall edge is noted as 23.11 (fig 2.4a) and it is translated on the solar shading protractor’s horizontal lines. The section opening is centred on the protractor and the angle of 23.11 is shaded (fig 2.4b)

Figure 2.4a Section of classroom with the angle

Figure 2.4b Shaded portion on the protractor

Step 2 Fig 2.4.c shows the daylight incident on the inner wall of the window /opening, the 82.57 is the angle generated and that is translated to the protractor on either side on the horizontal path to create a shading mask.

Figure 2.4c Section of classroom with the angle

Figure 2.4dShaded portion on the protractor

Step 3 Now, to determine the interior daylight incident on the plan of the classroom, a line is drawn to the inner wall making 79.21. This angle is further drawn on the protractor to get the final shaded region for our sample classroom. Refer below figure.

Figure 2.2e Section of classroom with the angle

Figure 2.4f Final Shaded protractor

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Step 4 To find the shading mask for our classroom located in Chennai, a stereographic sun path of 13 N (latitude of Chennai) is taken. The figures describe the steps to be done to determine the shading mask sun path diagram for Classroom in Chennai for East direction.

Figure 2.4g Stereographic sun path diagram for 13N East.

Figure 2.4h Final shaded protractor rotated

Figure2.4i Shaded protractor is placed on the sun path to find the shaded mask diagram for our classroom located in Chennai, India.

Step 5 Like the above steps, the final shaded mask diagram for our classroom is determined and is given in the figure 2.4.5a to 2.4.5d.

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Figure 2.4.5a Shading mask diagram – North

Figure 2.4.5c Shading mask diagram – West

Figure 2.4.5b Shading mask diagram – East

Figure 2.4.5c Shading mask diagram – South

Results From the above fig, we can infer that east and west orientation receives considerable amount of daylight, but the risk of overheating and glare is more, whereas the south orientation receives ample sunlight from 7 to evening 5.30 during March, April which is summer season. It is not suitable to have openings, and fenestrations and orientation in the south. Thus, the fenestration oriented to the north receives less direct sunlight, moreover, IS: 7942 - 1976 describes that buildings to be of north orientation as it minimises heat against the windows as well maximizes daylighting. It is found that sample classroom generated a DF of 1.99 % which is below the brief’s target, not uniformly distributed light as per section 2.2 and from the Shading mask diagram we found the best orientation is North.

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3 DYNAMIC DAYLIGHT MODELLING AND METRICS To examine the stage 2 initial daylight analysis, CBDM (Climate based daylight Metrics) simulations using Dynamic daylight Analysis Tool are used to find the most optimal configuration. Different iterations were done systematically as given in the Table3.1, the tabulated results are in Table 3.2 and detailed values can be seen in the appendix. The limitations are no windows can be added on the other walls, no change in floor plan, and ceiling height of 4m maximum. Table 3.1 Tabulated iteration parameters and outcomes Iterations Note

Modelling parameters / Adjustments

Results

The duration of the simulation shall be 8.00 am until 3.30 pm throughout the week and include holidays and weekends.

Each iteration is systematically done to get enhanced results that meets the briefs target

The modelling assumptions made were: • Double glazed clear windows • Chennai Weather file (IND_Chennai.432790_IWEC.epw) Room reflectance as per brief/standard, Walls: 45-50 percent, Ceiling: 70-75 percent, and Floor: 25-30 percent. are used for simulation. Although the clear double-glazed windows were used for modelling purposes, the schools’ operating and maintenance a dirt factor of 0.76 was excluded from the 3rd iteration. Note: Though working plane from 600 to 900mm are acceptable in classroom, a working plane of 700mm is considered for this work as the children are 11 to 19 years old, they require a desk height of 700mm and seat height of 450mm, the working plane is the desk height used. SIM001

Base model- North orientation with windows on the East – The model is drawn, and the modelling parameters are set as per the stage 2 table

Not optimum Daylight factor <2.5 % and ASE >10% and glare

SIM002

North orientation with windows on the North- The parameters was like SIM001.

Not optimum Daylight factor <2.5 % and SDA50/300 <55 (acceptable range) and increased dependence of supplementary lighting (UDI-s)

SIM003

North orientation with North windows – Reflectance and transmittance values are changed.

Sufficient DF > 2.5, But requires a supplementary lighting as UDI s = 88.2%, Acceptable ASE (<7)

SIM004

North orientation with North windows – same reflectance as SIM003 with a ceiling height of 4m

DF below target, but no supplementary lighting required (UDIs), Acceptable ASE (<7)

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SIM005

North Orientation with North window– 3.2m ceiling height but sill raised to 900mm and same window sizing 1.6m x 2.3m. To note: working plane kept as 700mm (desk height) When the working plane is raised to 900mm the results vary.

Insufficient DF <2.75 Requires supplementary lighting and minimal excessive light and Acceptable ASE. 900mm working plane – Daylight<2.75, Requires electrical lighting and more excessive lighting near the windows (UDIe), Acceptable ASE. (<7)

SIM006

North Orientation with North window -Window size reduced to 1.6x2.1m with sill 600mm

SIM007

North orientation with North window – 3m ceiling with wide window size (breadth increase) i.e., 1.8 x 2.1m

SIM008

North orientation with North window – 3m ceiling with wide window size (breadth increase) i.e., 1.8 x 2.1m with 3 dividers of 25mmx 50mm each, with glazing width of 500mm each.

SIM009

North orientation with North window – 3m ceiling with wide window size (breadth increase) i.e., 1.8 x 2.3m

SIM010

The same model as SIM007 but oriented to West with South opening.

DF is very less <1.5, SDA50/300 is lesser than acceptable (<55) range, ASE3.9, is in the acceptable range, increased dependence on electrical lighting but no glare/ negligible excessive light. Satisfies the UDIa (110 to 2200 lux)

Model meeting the brief target, with excessive light of 2.1 % (UDI e), Sufficient ASE (<10) Model meeting the brief target, with negligible excessive light 0.1 % (UDI e), Sufficient ASE (<10) Model meeting the brief target, with excessive light of 2.3 % (UDI e), Sufficient ASE (<10) Good DF but excessive glare, ASE >10 and requires artificial light at the rear end.

Similarly, other directions were tested, which ended up with results much higher and not suitable.

900

Figure 3.1 Showing 3d model with dimensions of SIM007,008 and 009 respectively.

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Table 3.2 Tabulated iteration parameters and values PARAMETERS

TARGET %

ORIENTATION

SIM001

SIM002

SIM003

SIM004

SIM005

SIM006

SIM007

SIM008

SIM009

SIM010

ADA

<2.75

1.63

1.65

2.89

2.46

2.45

2.5

1.39

2.95

2.77

3.14

2.95

SDA

>75

58.5

49.6

96.6

69.3

83.7

78.9

46.4

99.8

99.7

99.8

UDI-S

<40

40.2

88.2

54.1

55.8

45.3

UDI-U

>75

88.6

90.5

88.2

89.3

88.3

99.5

94.3

85.7

88.3

84.6

97.9

UDI-E

0.4

13.9

12.3

0.7

2.1

0.1

2.5

24.3

ASE

<10

31.3

6.1

5.6

6.1

6.9

6.1

3.9

7.1

7.3

13.6

MODIFIED

Base model

Base with N

Diff R values

4m Ceiling

Sill900mm

WP 0.9m

Small window

Wide window

Window partition

Tall & wide window

South window

BEST ORIENTATION

YES

Optimal orientation was selected as North in stage 2 initial analysis, the alternate hypothesis was tested in iterations SIM001 and SIM010, where the orientations were North with east windows and the latter with West orientation and south windows. It can be inferred from Table 3.2 that the DF is as low as 1.63, thus UDI-s is more, demanding more artificial light, but the ASE is above 10% which causes discomfort. On the contrary in SIM010, the DF is 2.95% but the lights are not uniformly distributed, hence, requires supplementary lighting at the rear end and excessive glare near the window region (UDI-e/ UDI 2000 is 24.6%), The ASE is 13.6% which is also above the 10 % threshold. Thus, on changing the orientation of window openings, the results are not satisfactory. SIM003 is the existing classroom with R values of 0.5,0.7,0.3 for walls, ceilings, and walls and 0.7 window transmittance. It should be observed that the DF and other metrics are meeting the target, but the UDI-s (UDI 100-300 lux) is 88.2%, which means the requirement of artificial lighting is more and the daylight is not uniformly distributed. However, in SIM009, when the windows are elongated from 1600mm to 1800mm with a height of 2300mm, and R values remaining the same as SIM003, the results are satisfactory.

Figure 3.2 SIM009 simulation results of aDA

Figure 3.3 SIM009 simulation results of sDA

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Figure 3.4 SIM009 simulation results of UDI-u

Figure 3.6 SIM009 simulation results of UDI-e

Figure 3.5 SIM009 simulation results of UDI-s

Figure 3.7 SIM009 simulation results of ASE

The SDA metrics are very good in all 3 cases (SIM007,008,009) as per table 3.2, >99 %, similarly, the UDI 100-300 metrics (UDI-s) is 0 % which means there is no necessity for supplementary/artificial lighting. UDI-e / UDI >2000 metrics enable in identifying spaces having above 2000 lux which causes discomfort and probability of glare. In SIM007 and SIM009 the UDI-e is 2.1 and 2.5 %, which is adjacent to the windows. In terms of ASE 1000 which Annual Sunlight exposure, in all the 3 cases it is within the sufficient level i.e., <10%, which means that less than 10% of the area has 1000 lux above the specified 250 hours. If it is more than 10 % it causes visual discomfort (Costanzo, Evola and Marletta, 2017). SIM008 Iteration satisfies the target the brief in stage 1, each window panel is 1800 x 2100mm with 3 partitions, leaving only 500mm clear viewing space for the students, thus, we can eliminate this option. Though the other iterations SIM007 and SIM009 satisfies the brief, the UDI-e are 2.1% and 2.5 % respectively. However, the ADF is more in SIM009, hence, considered as the final option. Refer Fig 3.2 to 3.7 for simulation results.

4 AN ELECTRIC LIGHTING STRATEGY From stage 3 inference, SIM009 requires no additional lighting as UDI-s is 0%. However, a lux level of a minimum of 500lux on the horizontal working plane is required to create ambient illumination for teachers and students to see in the absence of natural light in classrooms. Moreover, to overcome the brief challenges of creating healthy lighting, an artificial electric lighting strategy is recommended in addition to daylighting.

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Design strategy A human-centric lighting design is chosen, where cool white light with blue wavelength (CCT >4000K above) and sufficient task lighting helps students stay alert and focused(Hansen et al., 2018). Furthermore, it is in line with their body’s circadian rhythm. Most effective lighting is dynamic LED fixtures that are suspended from the ceiling at regular intervals as given in fig 4.1, these LEDs have a CRI >90, the fixture chosen has UGR<19 which means the luminaire has anti-glare properties making it child friendly. Since children are more attracted to white cool colours and since their eyes are at a formative stage of development, continuous exposure may lead to vision loss (Proykova, Samaras and Bruzell, 2018).

Fig 4.1 Artificial lighting design in optimised classroom

Fig 4.2 Reference of pendant light C95-P240x1200/1500 (Glamox, no date)

Photoelectric daylight linking is done with automatic sensors. Rectangular 1500mm length lights are suspended from the ceiling, they are integrated with DALI (Digital Addressable Lighting Interface) and motion sensors. Moreover, an additional wall lighting fixture LED with low glare is placed on the wall for emergency purposes. This motion sensor lighting enables better efficiency and switches on and off based on occupancy detection as well as based on the outdoor lighting levels. These have automatic dimming controls that minimize the luminance level based on daylight. These lights are both up lighting as well as downlighting. Hence, they help students with task performance as well light up the ceiling with uniform distribution of cool white light.

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Fig 4.3 Pendant type of LED luminaire (FAGHERHULT)

Fig 4.4 classroom reference image

The fig 4.4 image with a recessed LED light fixed in a suspended false ceiling at regular intervals can also be used. It must be noted however, provision of false ceiling requires ceiling depth, as we have only 3m height, the windowsill is at 2.9m, the proposed option of pendant lighting with dynamic LED light is most suitable.

5 SUMMARY OF FINDINGS AND REVIEW The brief speaks about the targets and metrics for healthy lighting in a classroom in Chennai, India. Stage 2 of initial analysis on the sample classroom specific to the region, gives a Daylight factor of 1.99 which is insufficient as per brief in table 1.5a. Additionally, it was found the lights were not evenly distributed. On finding the optimal orientation through sun path solar shading mask diagram for Chennai, North orientation and openings showed less direct sunlight and required minimal shading. It can also be noted that different countries have different recommendations, for instance in Chennai, India, is a warm-humid temperate climate, the primary aim of any classroom is to provide sufficient lighting and avoid glare and avoid thermal heat gains. This is in contradiction to the UK, where south openings and windows are preferred to invite sunlight and heat gains. Hence in stage 3, the best orientation of the classroom was also found out using CBDM tools and simulations, that North opening with north orientation is the most suitable and satisfies the briefs criteria. However, in practice, openings are also placed on the east, west side, but they are supplemented with shadings/ overhangs. The longer sides of the buildings are oriented in the North to south direction to minimize the solar heat gain as well as to allow maximum ventilation (Subramanian and Kamalesvari, 2016). Optimized classroom SIM009 has a UDI-e of 2.5%. The illuminance of 2000 lux above is primarily near the windows. These can be minimized by using manually controlled partial louvers or overhangs. (Costanzo, Evola and Marletta, 2017). In a practical and per standards the sill levels preferred are 900mm to 1200mm for a building with ceiling height of 3m to 3.5m. This is in contraction to the standard of optimum lighting level standard when observed in stage 3 iterations (refer table 3.2). The results from stage 3 shows a 900mm sill with acceptable levels of ASE i.e., <7%, but they had UDI-e > 10% and surprisingly 50% of the classroom required supplementary lighting. These highlights the importance of interior colours and finishes, window orientation, ceiling height. (Zhang et al., 2020) discusses the advantages of dynamic LED lighting on human health. Similarly,(Proykova, Samaras and Bruzell, 2018)speaks the ill effects of LED where long-term effects of blue light on children and occupants in general. Other contractions that can be found in current works of literature are that researchers claim that warm CCT like yellow colour and low

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intensity light helps in feeling relaxed, improves social behaviour, reduces restlessness and aggression and aids students with a learning disability (Boray, Gifford and Rosenblood, 1989). But this contrasts with the current brief and standard which requires cool blue light and what we consider best practice. The Limitation of brief further constraints in knowing the effects of different forms and their impacts in achieving daylighting, the aspect of glare is excluded in this report.

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REFERENCES van Bommel, W. J. M. and van den Beld, G. J. (2004) ‘Lighting for work: A review of visual and biological effects’, Lighting Research and Technology, 36(4), pp. 255–269. doi: 10.1191/1365782804li122oa. Boray, P. F., Gifford, R. and Rosenblood, L. (1989) ‘Effects of warm white, cool white and fullspectrum fluorescent lighting on simple cognitive performance, mood and ratings of others’, Journal of Environmental Psychology, 9(4), pp. 297–307. doi: 10.1016/S0272-4944(89)80011-8. Cajochen, C. and Wirz-justice, A. (1996) ‘Cajochen C , Brunner DP , Kräuchi K , Graw P , WirzJustice A . Power density in theta / alpha frequencies of the waking EEG progressively increases during sustained wakefulness . Sleep 18 ...’, (March 2015). Cannon-brookes, S. (2019) ‘Daylighting : simple methodologies Who is responsible ?’, (January). Costanzo, V., Evola, G. and Marletta, L. (2017) ‘A review of daylighting strategies in schools: State of the art and expected future trends’, Buildings, 7(2). doi: 10.3390/buildings7020041. Education Funding Agency (EFA) (2014) ‘EFA Daylight Design Guide’, (January), pp. 1–15. Available at: https://www.gov.uk/government/publications/efa-daylight-design-guide. Fotios, S. (2015) ‘Human Factors in Lighting, 3rd ed.’, Lighting Research & Technology, 47(4), pp. 507–507. doi: 10.1177/1477153515585285. Ghosh, A. and Neogi, S. (2017) ‘Impact of dust and other environmental factors on glass transmittance in warm and humid climatic zone’, Clean Technologies and Environmental Policy, 19(4), pp. 1215–1221. doi: 10.1007/s10098-016-1302-0. Glamox, T. (no date) ‘Slim and minimalistic Glamox C95 – One family , unlimited options’. Hansen, E. K. et al. (2018) ‘The impact of dynamic lighting in classrooms. A review on methods’, Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST, 229(January), pp. 479–489. doi: 10.1007/978-3-319-76908-0_46. Harle, D. E., Shepherd, A. J. and Evans, B. J. W. (2006) ‘Visual stimuli are common triggers of migraine and are associated with pattern glare’, Headache. doi: 10.1111/j.1526-4610.2006.00585.x. Heschong, L., Wright, R. L. and Okura, S. (2002) ‘Daylighting impacts on retail sales performance’, Journal of the Illuminating Engineering Society, 31(2), pp. 21–25. doi: 10.1080/00994480.2002.10748389. Hobday, R. (2008) ‘Hippocrates, town planning and the sun’, Journal of The Royal Society for the Promotion of Health, 128(1), pp. 19–20. doi: 10.1177/1466424007085220. Hobday, R. A. (1997) ‘Sunlight Therapy and Solar Architecture’, Medical History, 41(4), pp. 455– 472. doi: 10.1017/S0025727300063043. Kisan, M. and Sangathan, S. (1987) ‘SP 41 (1987): Handbook on Functional Requirements of Buildings (Other than Industrial Buildings) [CED 12: Functional Requirements in Buildings]’. Kisan, M. and Sangathan, S. (2010) ‘&quot;प0 रा1 को छोड न’ 5 तरफ&quot; &quot;जान1 का अ+धकार, जी1 का अ+धकार&quot; &quot;!ाान एक ऐसा खजाना &gt; जो कभी च0 राया नहB जा सकता है &quot;’ Available at: https://ia601007.us.archive.org/9/items/gov.in.is.sp.72.2010/is.sp.72.2010.pdf. Müeller, H. F. O. (2013) Daylighting, Sustainability, Energy and Architecture: Case Studies in Realizing Green Buildings. Elsevier. doi: 10.1016/B978-0-12-397269-9.00009-8. Nabil, A. and Mardaljevic, J. (2005) ‘Useful daylight illuminance: A new paradigm for assessing daylight in buildings’, Lighting Research and Technology, 37(1), pp. 41–59. doi:

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10.1191/1365782805li128oa. Neubauer, J. (2001) ‘Highlighted Topics’, Journal of Applied Physiology, 90, pp. 1593–1599. Available at: http://www.ncbi.nlm.nih.gov/pubmed/11007556. Proykova, A., Samaras, T. and Bruzell, E. M. (2018) ‘Potential risks to human health of LEDs (Final Opinion) Thermolumescence Dosimetry View project water-in-toluene emulsion film View project’, (June). Available at: https://www.researchgate.net/publication/326546236. Standards, I. (1976) म ाा नक. Subramanian, C. V and Kamalesvari, S. (2016) ‘Daylight and Sustainable Architecture for Warm Humid climate’, (December 2016), pp. 1381–1387. Walrand, S. (2021) ‘Autumn COVID-19 surge dates in Europe correlated to latitudes, not to temperature-humidity, pointing to vitamin D as contributing factor’, Scientific Reports, 11(1), pp. 1–9. doi: 10.1038/s41598-021-81419-w. Young, J. (2014) The Importance of a Positive Classroom, ASCD. Zhang, R. et al. (2020) ‘Impacts of dynamic led lighting on the well-being and experience of office occupants’, International Journal of Environmental Research and Public Health, 17(19), pp. 1–27. doi: 10.3390/ijerph17197217. Cannon-Brookes, D. S., 2021. Lecture 4 Daylighting: simple methodologies, London: Lecture notes.

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APPENDIX The Simulation record sheets with parameters for all the iterations are attached in the appendix. The simulation outcomes of SIM001 & SIM010 are attached as they drastically vary from brief.

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Simulation results of SIM001

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Simulation results of SIM010