THE IMPACT OF VARIED ORIENTATION AND WALL WINDOW RATIO (WWR) TO DAYLIGHT DISTRIBUTION IN RESIDENTAL ROOMS

Sharifah Fairuz Syed Fadzil School of Housing Building and Planning

Universiti Sains Malaysia, Penang, Malaysia E-mail: sfsf@usm.my

Adel Abdullah School of Housing Building and Planning

Universiti Sains Malaysia, Penang, Malaysia E-mail: aao.rd08@student.usm.my

Wan Mariah Wan Harun School of Housing Building and Planning

Universiti Sains Malaysia, Penang, Malaysia E-mail: mariah@usm.my

ABSTRACT

Natural lighting requirements for rooms in Malaysia are according to the Unifrtn Building by Laws (UBBL). This researclr analyzes tlre sufficiency of this by law on the requirement of natural Iiglrting for rooms and suggests ways how tltey can be improved Two rooms of tlre Fajar Building at the University Science Malaysia campus were wed as case studies and the effect of varied orientation and window to wall ratio WWR along with the percentage of window to floor area were studied. The dayliglzt factors were calculated and illumination levels were assessed comparing the different orientation and the mod~yed window area. Study concluded that wall window ratio W R of 50% and 25% and the corresponding window to floor area of 35% and 17% for rooms in tlre Malaysian context lrave dayliglrt levels exceeding the suggested standards. The by law tltat requires openings for daylight be 'not lessy may now be adjusted to 'not more' tlran 10% of total floor area became of tlre nature of tlre bright Malaysian skies. Tltis is to prevent tlte implications of glare and over lit rooms.

Keywords: (Dayliglrt factor, UBBL Uniform Building By Law, illumination level, WWR Wall Window Ratio)

1.0 INTRODUCTION

In buildings, windows are designed primarily for these functions of admitting daylight, enjoying the views and allowing for cross ventilation. In the tropics, glazed windows should be designed with care because glazing also allows heat admittance very easily through the processes of radiation, conduction and convection. Glare is another problem which occurs if the glazing is unprotected by any shading devices.

The three requirements for quality in day lighting design are satisfactory balance of brightness throughout the room, the right proportions of direct and indirect light, and absence of glare from sky and sun. The aim for good lighting in any design is to help the users see well, clearly and comfortably in any of the many varied tasks they may undertake.

Standards are set for recommending these lighting levels that are appropriate and that are usually being considered for efficient lighting practice. Table 1 below lists the suitable lighting for the performance of a range of tasks taken from the Malaysian Standards MS I525 2001. There are

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also other international lighting standards like by CIBSE (Charted Institute of Building Services Engineers) and ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers).

Table 2 Recommended Average Illuminance Levels

Task

Lighting for inffequent used area

Lighting for working interiors

Localized lighting to exacting task

Illuminance (Lux) 20 50 100 150 200 150

1000 I Exacting drawings

Example of application

Minimum service illumination Interior walkway and car park Hotel bedroom Entrance and exit Infi-equent reading and writing Restroom

100 150 - 300

2.0 THE DAYLIGEfT FACTOR AND THE MALAYSIAN UNIFORM BY LAWS

Bedroom Kitchen

The Daylight factor is a method that can be used as a basis for lighting design. It is given by the formula DF = Ei/Eo X 100 whereby it is the ratio of the illumination at any given point in the interior to the illumination on an unobstructed plane at ground level outside (CIBSE 1982). The daylight factor is appropriate for conditions where cloudy skies predominate @RE Building Research Establishment 1986). The skies in Malaysia are mostly overcast being in hot humid region with a lot water bodies.

Buildings constructed in Malaysia are being governed by the Malaysian Uniform Building By Laws and for natural lighting, the by law below prevails: "Every room designed, adapted or use for residential, business or other purposes shall be provided with natural lighting and natural ventilation by means or one or more windows having a total area of not less than 10% of clear floor area of such room and shall have openings capable of allowing a free uninterrupted passage of air of not less than 5% of such floor area."

With this by law, the openings for natural light can be from 10% up to 100%.Studies need to be conducted to analyse whether this 10% is sdficient for natural lighting of rooms and should there be an upper limit as in the tropical context too much light may not be desirable at it will introduce heat and glare problems as well.

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2.1 The Fajar Building at Universiti Sains Malaysia

University Science Malaysia is located in Penang Malaysia with a latitude of 5.3 degree North and a longitude of 100.3 degree East. (Figure 1) Malaysia, in general, has equatorial and hot humid climate with diurnal air temperatures ranging 24 - 34 degee Celcius and approximately 12 hours daily daylight duration that are generally similar throughout the year. These bright daylight hours were occasionally made dull by rainy and overcast days. The site map of University Science Malaysia is given in Figure 2 with the location Fajar building highlighted.

In this study, the Fajar residential building was taken as case study and two rooms were taken as samples as typical rooms that can exemplify the rooms suggested in the UBBL above. The rooms on the top most floor were used as they had typical overhang of the roofs which were similar. The room faced East and West directly and these directions were envisioned as being the worst case in terms of direct sunlight penetration and heat gains to the buildings in this particular climate. The plan and section of building are given in Figures 3 and 4. . - ~ - ~ ~ . ~- ~ ~ - - -. .

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From Figures 7 and 8 the rooms measure 2.9m by 4.43m with floor area of 12.85meters square. The window area is 4.43 meter square which makes up 50% of window wall ratio and 35% of window floor ratio. When half covered the windows make 25% WWR and 17% of window floor ratio thus exceeds the requirements of the UBBL for openings in rooms.

2.2 The Aims and Objectives of the Study

The main aim of this study is to analyse daylight distribution in a typical room in the context of Malaysian skies. It also aims to study whether the by laws relating to opening sizes for rooms in the Malaysian context are sufficient to provide optimum day lighting levels for normal daily functions.

The study has several objectives amongst them :

To compare the effect of orientation to daylight levels comparing the East and West orientation To compare whether the lighting requirements set by UBBL for natural lighting is suflicient for the Malaysian context To compare the effect of modifying the window or glazed area to the illumination level inside the rooms

Figure 2: Penang Island Malaysia with the location of USM circled

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Figure 2: Site Map of the Campus of USM with the Location of Fajar Building Circled

Figure 3 Part of the building plan at Fajar with the Figure 4 Cross section of the Fajar building studied rooms indicated with the studied rooms indicated

Figure 5 Picture of Fajar Building (facing East) Figure 6 Picture of Fajar building facing West

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Figure 7 The Babuc instrumental set-up (West room) Figure 8 The location ofthe outdoor illumination probe

3.0 METHODOLOGY

In this study the wall window ratio (WWR) of the rooms were calculated. Indoor natural illumination data were taken at East room (Le) and west room (Lw) simultaneously to be compared with outdoor illumination Lo. These data were collected using the Babuc M data logger that were connected to 2 indoor luxmeter probes with a maximum reading of 20,000 lux and an outdoor luxmeter probe with maximum reading of 100,000 lux. Readings were set to be collected digitally every 10 minutes and continuously for 15 days fTom March 7th 2009 to March 21st 2009. Locations of probes are shown in Figures 3,4,7 and 8

The month of March was chosen for data collection as March is the one of the hottest months in Malaysia however there were some rainy days in the period. The existing WWR of both Fajar rooms were calculated to be 50%. The window to floor area ratio were calculated to be 35%. Le and Lw were compared with Lo and data on the respective %DF (Percentage Daylight Factors) were derived.

The windows were then covered by polystyrene boards to modify the existing WWR to 25% and a window to floor area ratio of 17% as illustrated in Figure 8. Data on Le and Lw were collection again to compare with Lo. Selected data on selected days were graphed out and graphs on Day 1 - 3 were on the rooms with WWR 50% and data on Day 4 - 6 were on the room with WWR 25%. Analysis on the %DF were also carried out.

Figure 9: Graphics illustration of the Fajar room with the existing WWR 50%

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Figure 10: Graphics illustration of the Fajar room with the modified WWR 25%

4.0 RESULTS AND ANALYSlA

Results were graphed out in Figures 11 and 12 below. From the pattern of the graphs it can be concluded that :

Indoor illumination at east rooms usually peaked at around 9 am while in the west room at around 5pm and this is an indication of some direct sunlight penetration according to the sun's orientation and altitude at the particular times.

Daylight factor calculations ie LeLo X 100 and LwLo X 100 were carried out and the readings which were seen to have the influence of direct sunlight were deleted. This is because the daylight factor calculations do not consider the component from direct sunlight. Readings which were too early in the morning and too late in the evening were also deleted due to the skies not being uniformly illuminated.

From the calculations it was found that for East rooms with WWR 50%, %DF ranged from 2 to 4% while in the west rooms fiom 1 to 3 % which seems to be slightly lower compared to the east room. The illumination levels for east room range from 600 to 1000 lux while for the west room fiom 400 to 900 lux. These readings clearly exceed the standard illumination suggested by the MS 1525.

When the WWR was reduced to 25% daylight distribution decreased too from 1 - 2% for the East room and from 0.5 - 1.5% for west rooms. Illumination on the other hand reduced from 300 - 500 lux for east room and 200 to 450 lux for west room. The illumination level is lower but more conforming to the standards set by MS 1525 but still on the higher scale. I

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I I Figure 11: Le andLw (lux) compared with Lo (Klux) for WWR 50%

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Figure 12: Le and Lw (lux) compared with Lo (Klux) for WWR25%

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5.0 CONCLUSIONS

Day lighting studies in Malaysian context is very crucial because excessive light to the interiors are also source of heat and glare especially in this hot humid climate. By laws need be revised and developed in context of their particular site and locality. More specific conclusions of this study include :

The pattern of the natural lighting levels in Malaysia is very dynamic and they usually follow the bell shape curve fiom sunrise to sunset peaking at noon hours with illumination mounting to 90,000 lux. Occasionally light levels drop due to rainy and gloomy hours. Due to the bright skies, 10% opening sizes may be sufficient for daylighting levels according to standards since in both cases of 35% and 17% lighting levels were found to exceed the standards required. More studies should be geared to study light distributions with openings less than 10% as a lower range can be derived that is proven to be acceptable to the lighting distribution

Authors would like to acknowledge and thank the Universiti Sains Malaysia and Desasiswa Fajar Harapan for supporting and cooperating with this research.

REFERENCES

Syed Fadzil, S.F, (1998) ' W a W Lighting Distribution in the Prototype Classrooms" Journal ofHBP, Vol. V. 1998.

Syed Fadzil, S.F. and S.J.Sia, (2004) "Sunlight Control and Daylight Distribution Analysis : The KOMTAR case study'' Building and Environment, Vol. 39 No 6 2004.

The Malaysian Building By Law UBBL as of 2008 International Law Book Services Kuala Lurnpur The Malaysian Standards MS 1525 2001 CIBSE Charted Institute of Building Services Engineers Code for Interior Lighting London 1084 ASHRAE American Society of Heating, Refrigerating and Air-conditioning Engineers Handbook of

Fundamentals 2000

Arftllror's Biography

Dr Sharifah Fairuz Syed Fadzil is an Assoc. Prof: with the Architecture Program at the School of Housing Bziilding and Planning at USM She $ currently the Chair of the school's Environmental Laboratory and she is currently undertakinn several researches in thefield of environmental building -

and modelling -