Illumination Condition and Work Efficiency in the … Condition and Work Efficiency in the Tropics...

PLEA2012 - 28th Conference, Opportunities, Limits & Needs Towards an environmentally responsible architecture Lima, Perú 7-9 November 2012

Illumination Condition and Work Efficiency in the Tropics Study on production spaces of Ready-made garments factories in Dhaka

MD. MOHATAZ HOSSAIN

1, PROF. DR. KHANDAKER SHABBIR AHMED

1

1Department of Architecture, Bangladesh University of Engineering & Technology, Dhaka, Bangladesh

ABSTRACT: The Ready-made garment (RMG) sector of Bangladesh employs a large number of people who labour in the

production spaces of garments factory buildings throughout the day. The economic viability of this sector largely depends

on the performance of the workers. Demanding compliance standards of buyers from various countries and a challenging

energy supply and demand scenario in the sector poses questions of sustainability and building design. Appropriate

Illumination conditions of these production spaces, quality as well as quantity of lighting suitable for the production

processes, is a major requirement of a proper working environment. Industrial processes in such indoor environments are

becoming highly complex; workers working under poor lighting conditions are usually exposed to a range of visual

problems with operating machines, textile sewing activities, ironing and other activities. Visual comfort for various

illumination levels has impact on total physical comfort condition and any physical discomfort influences the human

behaviour and their work efficiency. The paper focuses on causality to identify the effects of the illumination condition of

production spaces on the work efficiency and to recommend illumination ranges that would facilitate optimum work

efficiency.

Keywords: Illumination condition, Work efficiency, Production space, Visual comfort, Ready-made garments.

INTRODUCTION

The readymade garment (RMG) sector is a fully export-

oriented industry [1] and Bangladesh is one of the largest

RMG exporters in the world. It plays a pivotal role in the

economy of Bangladesh by accounting for approximately

76% of the total export earnings and nearly 10% of GDP

[2]. Bangladesh, being a labour-abundant country, started

the process of industrialisation in the sector by

concentrating on labour-intensive products such as

clothing [3]. Hence, the economy of this sector depends

on the production by the workers. However, the

readymade garments have been heavily criticized during

1970 - 2000 for the poor working conditions particularly

in the production spaces. The poor luminous

environment in production spaces was one of the

concerns affecting the workers. Among the

environmental compliance factors Illumination condition

remain an important which must be ensured by the

factory owners. Illumination condition includes the

quality as well as quantity of the lighting. However, in

the production space (Sewing, Cutting, dyeing and

finishing), where illumination condition is very

important, the total luminous environment usually varies

with the type of lighting sources and location of the

sources. Poorly designed and maintained lighting can

result in glare and flicker that may cause vision

problems. When the lighting meets both quantity and

quality needs, it adds better working performance and

productivity [4]. Therefore, appropriate illumination

condition should be maintained not only for the visual

comfort but also for facilitating production targets..

The luminous environment acts through a chain of

mechanisms on human physiological and psychological

factors, which further influence human performance and

productivity [5]. Many factors, such as skill, education

and previous experience can affect productivity.

However, lighting is one of the least expensive and the

most important influences on human performance in the

work environment [6]. Providing workers with sufficient

light to perform visual tasks improves their accuracy,

thus increasing production speed and reducing waste of

materials and time. Total production process in the

garments factory constitutes several discrete stages of

activities which are linked in a progressive manner

forming a chain of labour intensive production process.

Therefore it is necessary to maintain an excellent work

environment for maximizing productivity [7]. While

considering the typical working environment of a

garments worker, light sources and illumination level at

the horizontal work plane are notable issues for this

research. Bangladesh National Building Code (BNBC)

and the local laws do not mention the means of achieving

recommended illumination levels. Since for compliance

needs, RMG factories in Bangladesh are increasingly

aiming to raise the lighting levels for various functional

needs like sewing, this is likely to increase energy

consumption substantially. Whereas, the general


whose age group is around 18-25 years in common and

who have experiences from 1 month to over 2 years with

an average 9-10 working hours per day.

Figure 2: False coloured 3D visualization showing the lighting

layout of the production space 3 (Software: DIALux)

Figure 3: Illumination condition of selected production spaces

EXISTING ILLUMINATION CONDITION Illumination levels were measured at different positions

within the selected production spaces. One set of

measurement was taken with the artificial lights switched

on (Figure 3), before the lunch break, and another with

lights switched off during the lunch break to test the

daylight penetration and its contribution to the

illumination condition of the production spaces during

day. All data were measured at the height of horizontal

work plane at 2.5 feet (0.76 m) above floor level. The

surveyed production spaces were divided into grids with

reference to column or structural grid. Then the points

gained in the 2D plan of the production spaces were

selected for recording of the overall lighting levels as

well as lighting levels where only source is daylight. It is

observed that the illumination level in production space

type-3 is a bit higher than the other spaces (Table 2). The

main reason behind it can be the overall artificial lighting

layout (figure 2), higher window lintel height which was

observed only in this production space, location of the

windows, outdoor illumination level, depth of the

production space and any other features impacting the

luminous environment. But variation (uniformity ratio)

of the lighting levels also can be observed in this

production space.

Table 2: Illumination level measured at horizontal work plane

Production

space

Location or zone Average

Illumination

level

(Daylight),

Lux

Average

Illumination

level

(Daylight +

Artificial

Light ), Lux

Production

Unit 1

Near the window (Party Daylight) 166 873

Centre of the half depth of space

(Mostly Artificial Lighting)

3 588

Furthest from the Window

(Completely artificial Lighting)

0 532

Production

Unit 2




9 672



1 581

Production

Unit 3




6 792



0 696

Table 3: Average Uniformity and Diversity of Luminance Production

Space 1

Production

Space 2

Production

Space 3

Uniformity of Luminance: (435/664)=0.66 (420/735)=0.57 (390/805)=0.48

Diversity of Illuminance: (1150/435)= 2.5 :

1

(1050/420)=2.5

: 1

(1490/390)=3.5

: 1

Table 4: Measured illumination levels and standards

Average illumination in survey Internatio

nal

Standards

( IESNA)

Internatio

nal

Standards

(IES

Code)

Local

Standa

rds

(BNBC

2006)

Produc

tion

space

1

Productio

n space 2

Productio

n space 3

Minimum

Illuminatio

n level at

work plane

(lux)

435 420 390 300 600 300

Maximum

Illuminatio

n level at work plane

(lux)

1150 1050 1490 1000 900 1500

While considering only the daylight in the production

spaces and uniformity ratio, it can be easily observed that

the uniformity ratio of daylight is very low in all the

production spaces. Hence, supportive artificial lights are

installed in the indoor spaces. These three production

spaces used florescent tube lights. Uniformity of

luminance, Diversity of Illuminance and Spacing Height

Ratio were calculated based on recorded illuminances

and other records during the surveys in the production

spaces. The mounted lights were at 7 feet (2.13 m) from

floor level at all the selected spaces. The Table 3 reveals

a uniformity of luminance of 0.48 in production space-3,

which is considered low. The diversity of Illuminance at

the work planes was also found high in production space-

3. The workers of the production space-3 may face more


glare or contrast problem than other production spaces.

The value of SHR is low in the production space-1 which

indicates good and glare-free artificial lighting

environment.

Table 4 gives comparison between ‘International

illumination standards' and ‘local recommendations' for

sewing or equivalent works which was then compared

with the illumination measured in the surveyed

production spaces. The illumination level comparison

shows that in the surveyed cases the highest levels are

reached in the work planes, though international

standards require less lighting in the work plane areas.

The usually recommended uniformity of luminance

should not be less than 0.8. But none of the production

spaces met this standard. On the other hand, while

considering the diversity of Illuminance, all the results

were within the standard of 5:1.

PERFORMANCE ANALYSIS AND RESULTS

The two main variables were taken from same samples at

the same time and ‘correlation’ analysis with other

available evidence was done by Microsoft Excel Data

Analysis. Here, the independent variable is the

illumination level and dependent variable is the number

of defects per hour (%). While doing statistical data

analysis to observe correlation among the variables

(Distance between luminaire and work plane (ft), Product

Colour at work plane, Number of Errors per hr (%),

Illumination (at work plane), and Lighting Environment),

limited degree negative correlation were found between

Illumination at work plane, Lighting Environment,

Number of Errors per hr (%). Limited degree positive

correlations were also found between Lighting

Environment and Illumination level (at work plane).

Table 5 revealed that the number of defects per hours

(%) has limited degree negative correlation with

illumination level in all surveyed production spaces. The

correlation coefficients (r value) in production space 1, 2

and 3 are -0.6,-0.5 and -0.5 respectively. On the other

hand, the correlation coefficients number of defects per

hours (%) and Lighting environment or zone in

production space 1, 2 and 3 are -0.3,-0.4 and -0.5

respectively. When considering the correlation between

lighting environment and lighting level, the value of the

coefficients (0.5, 0.7 and 0.6 in the production space 1, 2

and 3 respectively) show that they have limited degree

positive correlation which reveals that inclusion of

daylight can cause increasing of total illumination.

To understand the causal relationship between these

two variables (dependent: number of defects per hours

(%) and independent: illumination level) the Scatter pot

chart with regression line and Detail regression analysis

were used. Relationship between the two variables can

also be exhibited graphically by scatter diagram. Figure 4

illustrates the linear relationship between the independent

variable (illumination level) and dependent variable

(Percentage of production defects per hour) within two

Axis X and Y respectively. From the comparison

between these individual scatter pot charts of three

production spaces, it can be observed that the mode of

the line, the slope of the equations have the similarities

and the illumination levels have moderate effect on the

efficient production. The Regression analysis statistics

can be shown by Table 6 where the values of ‘R Square’

were identified. In production space-1, R square value

reveals that illumination level had about 36% (0.362 out

of 1) causal effect on the production defects (output

variable). Rest of the cause could be other environmental

variables and personal factors. In production space-2 and

3, R square values shows that illumination level had

about 25% (0.251 out of 1) and 20% (0.201 out of 1)

causal effect on the production defects (output variable).

Table 5 Correlation coefficients among illumination levels,

lighting environment and production errors per hour

Su

rveyed

un

it

Variables

Distance

between

Luminaire

and work

plane

Product

Colour

at work

plane

Number

of

Errors

per hr

Illumination

level (at work

plane)

Lighting

Environm

ent P

rodu

cti

on

un

it 1

Distance between

Luminaire and

work plane 1.000

Product Colour

at work plane 0.618 1.000

Number of

Errors per hr 0.314 0.270 1.000 Illumination

level (at work

plane) -0.025 -0.098 -0.611 1.000 Lighting

Environment 0.265 0.074 -0.323 0.450 1.000

Pro

du

cti

on

un

it 2

Distance between

Luminaire and

work plane 1.000 Product Colour

at work plane 0.116 1.000 Number of

Errors per hr 0.145 -0.091 1.000 Illumination

level (at work

plane) -0.070 0.038 -0.514 1.000 Lighting

Environment -0.149 -0.162 -0.441 0.680 1.000

Pro

du

cti

on

un

it 3

Distance between

Luminaire and

work plane 1.000 Product Colour

at work plane 0.035 1.000 Number of

Errors per hr -0.264 -0.049 1.000 Illumination

level (at work

plane) 0.219 0.040 -0.463 1.000 Lighting

Environment 0.047 0.223 -0.476 0.591 1.000

From Regression of these two variable (independent

variable: Illumination level and dependent variable:

Production errors), coefficients (B value) were found as

well. It can be observed that increasing 1 unit of

illumination level, causes 0.009 units less defects in

production space-1, 0.007 units less defects in production

space-2 and 0.005 units less defects in production space -

3 (


Table ). In terms of percentage, it can also be said that

increasing 10 unit of illumination level causes 9% less

defects in production space-1, 7% less defects in

production space-2 and 5% less defects in production

space -3. Frequency analysis of independent variable

(illumination level) of the samples with bin ranges from

200 lux to 1200 lux and more reveals that high frequency

samples had 401-1000 lux at their work-plane in

production space-1, 2 and 3. Frequency analysis in bar

charts explain that for production unit 1 and 2, the

desired lighting for effective production is 601~800 lux,

while for production unit 3, it is 801~1000 lux.

Figure 4: Scatter pot chart showing correlation between the

two variables with linear regression lines and linear equations

Table 6: Regression Statistics of two variables Surveyed Units Regression Statistics

Production unit 1 Multiple R 0.611

R Square 0.373

Adjusted R Square 0.362

Standard Error 2.296

Observations (N) 60


R Square 0.264



Observations (N) 60


R Square 0.214



Observations (N) 60

Table 7: Coefficients from Regression analysis Surveyed

Units

Independent and

Dependent Variables*

Coefficients

(B Value)

Standard

Error t Stat

Production

unit 1 Intercept 10.979 1.154 9.518

X Variable 1 -0.009 0.002 -5.876

Production

unit 2 Intercept 8.157 1.054 7.740

X Variable 1 -0.007 0.002 -4.563

Production

unit 3 Intercept 7.608 0.992 7.669

X Variable 1 -0.005 0.001 -3.975

* Independent variable: illumination level and dependent variable: production

defects per hours (%)

On the other hand, while considering location of the

sample workers in terms of lighting environment or zone,

highest numbers of the samples had low production

defects within partly natural light in the production

space-1. In production space-2, low production defects

were observed in mostly artificial lighting environment,

while in production space-3, low production defects were

notices in partly natural environment. The production

space configuration in terms of window location,

available daylight inside the production space can be one

of the reasons behind this result.

Table 8: Descriptive Statistics of effective lighting levels Illumination level (at work plane) with low production defects, Lux

Production unit 01 Production unit 02 Production unit 03

Mean 835.9 724.8 898.8

Standard

Deviation

159.6 145.6 265.9

Minimum 520.0 425.0 390.0

Maximum 1150.0 1028.0 1490.0

Count 20.0 35.0 33.0

On the other hand, while considering location of the

sample workers in terms of lighting environment or zone,

highest numbers of the samples had low production

defects within partly natural light in the production

space-1. In production space-2, low production defects

were observed in mostly artificial lighting environment,

while in production space-3, low production defects were

notices in partly natural environment. The production

space configuration in terms of window location,

available daylight inside the production space can be one

of the reasons behind this result.

Table 9: Frequency of only those lighting environment with low

numbers (0%~3%) of defects using bin function Lighting environment Bin* Production

unit 01

Production

unit 02

Production

unit 03

Completely Artificial

lighting environment -2 2 13 3

Mostly Artificial lighting

environment -1 0 18 5

Partly Natural lighting

environment 0 21 4 22

*Here,-2,-1 and 0 are the dummy variables (bin ranges within -2 ~0) for the

convenience of statistical analysis.

The correlation coefficients revealed that there were

causal relationships between the illumination condition

and the work efficiency. Through the regression analysis

the relationship established a linear equation y=mx+c,

where ‘x’ and ‘y’ are the two variables, ‘m’ is the slope

and ‘c’ is the intercept of ‘y’. Slopes are from -0.0091 to

y = -0.0091x + 10.979

0 1 2 3 4 5 6 7 8 9

10 11 12 13

300 400 500 600 700 800 900 1000 1100 1200

Per

cen

tag

e of

Pro

du

ctio

n d

efec

ts

per

hou

r (%

)

Illumination Level at work plane (Lux)

Production defects vs Illumination level (Production unit 1)

y = -0.0071x + 8.1569

0 1 2 3 4 5 6 7 8 9

10 11

300 400 500 600 700 800 900 1000 1100

Per

cen

tage

of

Pro

duct

ion

def

ects

per

hour

(%)


Production defects vs Illumination Level (Production unit 2)

y = -0.0049x + 7.6085

0 1 2 3 4 5 6 7 8 9

10 11

300 500 700 900 1100 1300 1500 Per

cen

tage

of

Pro

duct

ion

def

ects

per

hour

(%)


Production defects vs Illumination Level (Production unit 3)


-0.0049 (Table 10). The minus (-) sign of the slope

indicates that increasing the illumination level decreases

the production errors. The value reveals that increasing 1

unit of illumination level causes 0.91%~0.49% less

defects. Within this scope of research, it was found that

probable efficient illumination ranges was commonly

601-800 lux. As the overall lighting levels in lighting

ranges were bit high in production space-3, the finding of

the ranges became high. Considering the mean values

and standard deviation from the mean values, it can be

said more specifically that the desired illumination level

at the work plane of the worker in production spaces to

achieve effective and quality production should be

around 700 lux (within range of 601~800 lux). However,

there must be no glare, veiling reflection or high contrast

at the work plane. Otherwise it could generate eye related

health hazards and reduce production.

Table 10: Comparative observation of the worker evaluation Terms Production

space-1

Production

space-2

Production

space-3

Sample

criteria

Number of Sample

workers

60 60 60

Sex M: 36%, F:

62%

M: 60%, F:

40%

M: 59%, F:

41%

Age group (Years) 18-25 18-25 22-29

Major Activity Name

(Sewing)

Operator

(75%)

Operator

(45%)

Operator

(43%)

Experience of sample

workers

More than 2

years

0.1-0.5 years 0.6-0.9 years

Total work hour

(hours/day)

9-10

hours/day

9-10

hours/day

9-10

hours/day

Linear

relationsh

ip

Causal relationship

between Illumination

level (x) and percentage

of production defects

per hour (y) , equation:

y=mx+c,

y = -0.0091x

+ 10.98

y = -0.0071x

+ 8.16

y = -0.0049x

+ 7.61

Ranges Illuminance ranges for

less defects (Lux)

601-800 601-800 801-1000

Mean Mean Illuminance for

less defects (Lux)

836 725 899

Standard

deviation

Standard deviation

(Illuminance for less

defects)

160 146 266

Quality of

light

Major Lighting

environment for less

defects

Partly

Natural light

(21)

Mostly

artificial

light (18)

Partly

Natural light

(22)

CONCLUDING REMARKS:

From this research, the following specific as well as

some general recommendations can be drawn for

production spaces of RMG factories in context of Dhaka

region, Bangladesh, in order to improve the luminous

environment as well as future study:

The illumination level at the work-plane of the workers

should be within 600-800 lux (average 700lux) especially

for Sewing Operators, Sewing Helper, Quality Controller

and others.

As illumination level and production defects have

negative linear correlations, low illumination level at

work plane must be avoided.

From this research it has been found that about

21~37% (0.21~0.373 out of 1) of the illumination

condition has the causal effect on effective production

capacity of the worker. Other aspects like thermal,

psychological, other environmental features should be

also considered during evaluation of the workers

performance with effective production in future research.

The luminaires layout and their spacing should be

designed by architects or designers in such a way that

uniform lighting and required lighting level with daylight

inclusion should be ensured at any point of the horizontal

work plane in the production space for flexible

production flow design.

Architects should design the production flow layout

within a production space in such a way that the critical

works, which require high lighting level to do the work

comfortably, can be placed near openings of the

production spaces to ensure better luminous environment

for the workers with better productivity.

This research was also conducted only in purpose

built RMG factories where the production spaces

maintain some certain environmental compliance.

Guidelines suggested in this paper can be considered by

the architects or designers while designing a standard

production space with accommodating compliances

possibly for LEED certification process or can be applied

during construction or renovation of the production

spaces.

ACKNOWLEDGEMENTS.

The authors acknowledge Bangladesh University of

Engineering & Technology and GIZ for their support.

REFERENCES 1. Absar, S. S. (2001) "Problems surrounding Wages: the

Ready-made Garment Sector in Bangladesh." Labour and

Management in Development Journal (Asia Pacific Press)

Volume 2, no. 7.

2. International Finance Corporation (2007) Ready-made

Garments: Challenges in Implementing a Sector Strategy.

Dhaka: Monitor, Bangladesh,

3. Trine, T. (2003), "TEXTILES design and production

development in Bangladesh, Report from a visit to Dhaka."

findebookee.com.. http://findebookee.com/t/textiles-design-and-

production-development (accessed 2010).

4. Northwast Energy Efficiency Partnership Inc. (2000)

Highbay Industrial Lighting: knowhow: Combining Quality

design and energy efficiency for warehouse and factory

Buildings. http://www.designlights.com.

5. Gligor, V. (2004), "Luminous environment and productivity

at workplaces." Thesis (Licentiate). Espoo: Helsinki University

of Technology,

6. Katzev, R. (1992), "The impact of energy-efficient office

lighting strategies on Employee Satisfaction and Productivity."

Environmental and Behaviour Volume 24: pp. 759-778.

7. Prokaushali Sangsad Limited (2007) Identification of eco-

Efficiency Measures for the Readymade Garments Factories in

Bangladesh. working paper no-2, GTZ Progress, Bangladesh

8. Zohir, S. C., and P. Paul-Majumder (2008), Garment

Workers in Bangladesh: Economic, Social and Health

Condition. Dhaka: Bangladesh Institute of Development

Studies.

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Illumination Condition and Work Efficiency in the … Condition and Work Efficiency in the Tropics...

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