Shading Device as Strategies Achieving Thermal Comfort for Office Building in Tropic

1

Shading Device as Strategies Achieving Thermal Comfort for Office Building in Tropic Mohd. Amir Asyraaf bin Zulkifli, M. Arch mohdamirasyraaf@graduate.utm.my

W. master:

Dr. Aminatuzuhariah Bte Megat Abdullah (b-zuhariah@utm.my)

Thesis Panel:

Dr. Malsiah Binti Hamid (b-malsiah@utm.my) Dr. Dodo Yakubu Aminu (yadodo@utm.my).

Department of Architecture, Faculty of Built Environment Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia.

____________________________________________________________________________ Abstract: Building aesthetic, thermal and noise reductions and wind protection are the main reasons to use shading device on buildings. Previous researchers have suggested that the risk of overheating within double-skin facade (DSF) as shading device envelope is high in tropical climate. However, some studies claimed that it can improve thermal comfort in tropics buildings. DSF performance is mostly studied in cold climate and there are a lot of literatures considering DSF in European and North American countries.

But its application in tropical and hot climate conditions is not studied enough. Therefore, this study aims to evaluate the efficiency of DSF in lowering solar heat gains in achieve thermal comfort in tropical climate of Malaysia.

Keywords: Energy Efficiency, Building Performance, thermal comfort, Passive Design, 1. INTRODUCTION

3. Night Time Ventilation integrated with DSF and

Building facade as an external part of building

thermal transfer of sun radiation.

maintains interaction between indoor and outdoor environment. In addition to separating inside environment from outside, the building facade keeps the building safe from unwanted weather conditions, control the amount of sunlight and solar heat

gains,

improve

building

acoustic

and

represent building aesthetic.

1.2 Building Energy Consumption Buildings consume more than 40% of the energy globally. Thermal performance of buildings is highly depended on windows configurations which are the weakest point of building envelope in terms of energy efficiency. Therefore, enhancement in

From the study of the shading device design and

window

its cavity depth, the main concern of this study

building energy efficiency.

includes 1. Energy savings, 2. Natural ventilation,

performance

considerably

improves

2 Global energy consumption and building industry

human being satisfactory of life and their

increased from 86 exa-Joules in 1971 to the

performance in working environment is highly

amount of 165 exa-Joules in 2002 with average of

depended on thermal comfort parameters that

growth was more than 2.2% per year where

includes environmental (air temperature, air

commercial and office sectors is 50% more than

movement, and humidity), personal (metabolic

residential sectors. Building energy consumption is

rate or activities and clothing) and contributing

depended on factors like climate condition,

factors (food and drinks, acclimatization, body

buildings form and buildings use. However, among

shape, subcutaneous fat, age and gender).

all of the climate based elements, temperature, humidity, solar radiation and wind affect the occupant thermal comfort directly.

The report from National energy balance MECM (2002) emphasized that the energy consumption growth two times faster in 90’s decade comparing with that amount for 80’s as in the period 1990 till

The ASHRAE 1997 apply a seven-point scale to measure human comfort from 1 means cold and 7 means hot.

Olgyay (1963) introduced his bio-climatic chart to represent

thermal

comfort

based

on

air

temperature, air movement, sun radiation and relative humidity on thermal comfort.

2000 growth three times ASEAN-USAID in 1992 conducted a research on building included office buildings, hotels, hospitals, supermarkets and retails energy consumption of office buildings in this region have an average of 233 (kWh/m2) while average of Malaysian energy consumption exceeded this average and reached the amount of 269 (kWh/m). Ramatha (1994) claimed that 52% of it spent for air-conditioning and 42% is spent for lighting.

Figure 1: Olgyay’s bio-climatic chart in metrics, modified for warm climates (Source: Introduction to Architectural Science, Szokolay (1998), p. 21)

1.3 Thermal Comfort Fanger (1970) defined the thermal comfort as a situation that people feel satisfaction with the thermal environment. As in recent decades, people spend most of their times in artificial climate while Ruck (1989) and Wong P.C (2008) stated that the

1.4 Malaysian Climate Malaysia experiences the hot and humid condition and heavy rainfall in most of the year ecause of its equatorial location. Dale (1963), Tick and Samah (2004), Wycherley (1969) and Samirah (1999) mentioned that annual temperature for all country

3 is 26.5 째C in average and the average of maximum temperature is between 29째C and 32째C while the weather condition during a year period has not significant changes with limited to 3째C. and the range of temperature differences between different parts of Malaysia is small (except mountain zone).

For humidity, Tick and Samah (2004) stated that average relative humidity of Malaysia varied between 70% and 90%.

2. Double Skin Facade (DSF) DSF is a building envelope consists of inner skin, outer skin and the cavity space between them. In some cases, the cavity space is naturally ventilated,

in

some

others

the

cavity

is

mechanically ventilated; also there are some cases without any ventilation strategies. DSF can be categorized based 1. ventilation strategies, 2. Shapes, 3. origin of air coming into the facade or going away through the facade openings and 4. form. Behzad. R, (2013)

1.5 Thermal Conduction Thermal conduction in buildings happen between

The performance of DSF is highly depended on its

solid materials like walls and roofs. The rate of heat

material, cavity depth, building location, facade

conduction transfer depends to thickness and

orientation, sun-shading devices and weather

conductivity of materials and the temperature

climate. DSF also is able to bring natural

differences between them. buildings convection

ventilation and improve user control and comfort

heat transfer mostly depends on airflow rate.

Chan, et al. (2009). Stec et al., (2005) and Gratia

According to Bulow-Hube and Lunch (2002) the

and Herde, (2007) recommended that the risk of

solar parameters like a solar position and solar

overheating within DSF envelope is high in tropical

intensity in one hand; and glazing properties in the

climate. This thesis aims to evaluate the efficiency

other hand determine the amount of follow rate

of DSF in lowering solar heat gains in tropical

through windows envelope. While solar radiation

climate of Malaysia.

reaches the surface of glazing then three cases are

possible;

transmittance.

reflectance

absorbance

and

In order to understand the state of the art knowledge in the field of DSF and its effect on building energy consumption previous researches were reviewed. Here the most important literature is presented in Table 1.

Stec (2004) Ding (2004) Gratia (2004) Perez Grande (2005) Hien (2005) Gratia (2006) Wong P.C (2008) Xiao-Li (2008) Frnando (2008) Baldineli (2008) Chan (2009) Huckeman (2010) Present study

Netherland Japan Belgium Spain

X

Singapore Belgium Singapore China Portugal Italy Hong Kong Germany Malaysia

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X X

X

X X

X

X X

X X

X

X

X

X

X

X

Table 1: Summary of previous study related to Double Skin Facade.

The study conducted will be more focusing on

gains in the case of non-air-conditioning office

difference in temperature or heat transfer on

building in tropical climate of Malaysia,

naturally ventilated DSF that act as Sun Shading. The hypothesis of this study is that “integration of DSF design on building facade will reduce the amount of solar heat gains into building surface thus lower down the energy use to cool the spaces in achieving thermal comfort with more efficient�.

The research is also to find the optimum type and design of DSF to achieve optimum temperature inside the office room, the effect of building orientation and solar time on DSF performance at specific date and day and the ability to reduce the solar heat gain by combination of shading device.

Based on the literature reviewed, without mechanically cooling and ventilating strategies it is very difficult to reach comfort zone for buildings in tropics. Considering the design of shading device, cavity size, orientation of building and during the four design days, its required a high amount of simulation to be done.

The

study

is

expected

to

show

the

effectiveness of the DSF configurations to reduce solar heat gains and consequently reduce rooms air temperature and provide suggestion

on

Mathematical

Simulation

X X

X

X

X

X

X

X

X

X

X X

X X

X

X

X

X X

X

X

X X

Full Scale

Energy

Thermal

Temperature

Air velocity

Thermal wall

X X

X

Tools

X X

X

X

Wind Speed

X X

X

X

X

X

X X

Glazing

Sun Shading X

X

X

X

Air Gap Size

Configuration

Not allowed

inside cavity

Inside building

Mechanical

Natural

Research

Ventilation Strategy

Performance Variables

Scale

Design variables

Opening Size

Climate Zone

appropriate

design

configurations on DSF system that can

This study is to assess and evaluate the impact

minimize energy consumption in office building

of DSF configurations on reducing solar heat

in Malaysia.

3. MODELLING & METHOD Simulations research are conducted is to study building geometry and DSF design in

Ecotect Analysis 2011 are used to study the relationship between amount of radiation, and the temperature of the space study.

effect with the temperature of space inside of

To find the sun angle of the site in four design

the building. It also may present the data on

days, SketchUp Pro 2015 and Ecotect 2011

lighting and average temperature without

are used to determine the angle of vertical

cooling system. The best advantage of

and horizontal direction. Geo Location

simulation researches comparing with case

coordinated 2.915127N and 101.681878E

study researches is its effect on reducing

are use as it was the specific location for

research cost and time, comparing with case

proposed site 4C2, Putrajaya, Malaysia.

study research.

Ecotect weather data from Ecotect Weather

Ossen (2005) analysed the amount of solar

Tool for Kuala Lumpur Malaysia are used as

radiation on vertical surfaces on West and

it was the nearest weather data available for

East is higher than North and South facade.

the site. The base model is developed in

Therefore, the aim of the simulation is to

Google Sketch Up before transferring to

provide the best suggestion for type of

Autodesk Ecotect Analysis.

shading device for certain oriented facade for specific day time that is from 8 a.m. to 5 p.m.

Figure 3: Shows the model use to study the sun angle using Ecotect software (left) and Sketchup software (right).

Figure 2: Shows the design work flow process.

4. RESULT & DISCUSSION

A model combination of 2 square are used to find the sun angle for the specific time, the result is use in developing the best shading device to be integrated with building. The shading device design estimated will provide sufficient daylight need for the space inside while reduce the amount of heat radiation.

Date 21-Mar 21-Jun 22-Sep 21-Dec

0800 Sun angle 0.20 SE Horizontal

1030

1300

1530

1700

2.60 SE

63.20 SE

3.7 SW

3.60 SW

Vertical

10.10

42.60

85.10

57.20

32.60

Horizontal

23.60 NE

31.00 NE

80.6 SE

35.20 SW

26.00 SW

Vertical

12.65

49.60

86.50

56.80

34.50

Horizontal

0.05 SE

2.70 SE

60.80 SW

3.20 SW

0.60 SW

Vertical

13.64

51.30

87.43

53.70

31.20

Horizontal

24.40 SE

36.20 SE

84.60 SE

50.30 SW

28.6 SW

Vertical

11.10

48.9

87.3

54.3

31.60

Table 2a 21 March

21 June

22 Sept

21 Dec

0900

1100

1300

1500

1630

1700

Table 2b Table 2a&b: Shows the result obtain of the sun angle by using Ecotect and Sketchup software.

From the study it is found that the optimum

involve visual tasks, such as reading and

fix shading device should be in ratio 10mm

writing, is within the range of 300–750 lux.

width with 1mm gap between them to cut the vertical sun angle and 37.5Ö rotated from north to cut the horizontal sun rays. As for sky

in

Malaysia

will

averagely

have

luminance level of 100 000 lux, the integration of shading device should allow around 60% diffusion of light as said by Balocco and Calzolari (2008) that the average value for paper-based activities that

As the result of the angle of the sun are obtain, the design of the shading device is studied in 4 situations that is without shading device, using horizontal shading, vertical shading and egg crate. The simulation is conducted at an office space facing west as stated by most author that the western facade is exposed to sunlight for longer time.

Min temperature

Max temperature

Mean temperature

No shading device

25.17

34.18

29.27

Horizontal shading device

25.19

34.04

29.26

Vertical shading device

25.18

33.78

29.17

Egg crate shading device

25.04

32.80

28.85

Table 3: Shows the temperature result in specific space study The result from the simulation shows that there is difference between the 4 situations stimulate where is with constant size and gap but different design, egg crate has the lowest mean temperature. From the study it can be stated that egg crate is the most suitable fix shading device to be use.

East

West

Depth (mm)

Gap (mm)

Horizontal

5

1

Vertical

3

1

Horizontal

5

1

3.5

1

Horizontal

1

3.8

Vertical

1

7

Horizontal

1

4.2

Vertical

1

6.5

Vertical North

South

Table 4: above shows the suggested gap and depth of fix shading device as the result from the study of the sun angle and the shadow effect of the building.

5. PROPOSED DESIGN

Figure 4: Shows the building orientation proposed.

The shape and orientation of the building are developed after few simulations are done by using Ecotect simulation software. As it is suggested that the best orientation for the building should be 17° from north and the worst is facing 127.5° from north.

By considering the vegetation that are preserved, site boundaries, wind direction that mostly come from west and movement of people nearby area, the ideal idea is to propose a building that is oriented 15° away from north.

1 2

Roof Photovoltaic panel.

South shading device are mostly horizontal louvers to cut the vertical sun rays.

West facade shading device cut vertical and horizontal sun rays while allow for view of the 3 Putrajaya lake from the office.

4 Cantilevered roof at temporary gallery to allow skylight into the building.

5 Preserved trees as part of shading and GBI strategies.

6 Green wall of Multipurpose hall in respect to orchid park across the road.

Pedestrians entrance into plaza and event space tap the pedestrian from the nearby 7 monorail station.

Water element located near the Event Space allow wind to bring cool breeze into the 8 building as most of the wind come from west direction.

9 Services are located at the east of the site as it blocked by the.

10 Main entrance and drop off facing the plaza and the preserve garden.

Plaza as spine that connect the pedestrian from the monorail station and the government 11 office area nearby.

Figure 5: Shows the perspective of the design without trees.

Figure 6 & 7: Shows the rendered perspective of proposed design with trees.

6. CONCLUSION In conclusion, it is proven that double skin facade system may reduce the radiation of heat onto building surface. Hence, it responded to the study which is effective shading device may contribute to lower heat absorption of the wall. With this statement being mentioned, it shows that Double Skin Facade system does correspond the idea of how shaded building can improve the energy efficiency of the building by enhancing the cooling effect in the building through its thermal performance. Therefore, the integration off shading device are very encourage as it lowers the building temperature and lead to better human comfort which result to sustainable and ecofriendly design.

REFERENCES Rahmani, Behzad (2013) Effects of double skin facade configurations on decreasing solar heat gains in high-rise office buildings in the tropical climate of Malaysia. PhD thesis, Universiti Teknologi Malaysia, Faculty of Built Environment.

Rahmani, Behzad (2013) How Double Skin Facade’s air-gap sizes effect on lowering solar heat gain in tropical climate.

Wong, P. C. (2008). A new type of double-skin fa9ade configuration for the hot and humid climate.Energy and Buildings Ruck, NC. (1989). Building Design and Human Performance. New York: Van Nostrand Reinhold Fanger, P.O. (1970). Thermal Comfort. Copenhagen: Danish Technical Press Dale, W. L. (1963). Surface temperature of Malaya, Studies of Geography in SEA. Samirah, A.R. (1999). Airflow and thermal Comfort Studies in Naturally Ventilated Classrooms in School in Malaysia. Unpublished PhD Thesis. Universiti Technology Malaysia Ossen, Dilsan Remaz (2005). Optimom Overhang Geometry for Controlling Penestration Heat Gain and Building Energy Saving in Tropics. Unpublished PhD thesis, Universiti Technology Malaysia Balocco C. (2004). A non-dimensional analysis of a ventilated double facade energy performance.

Energy and Buildings.

C. Balocco, and R. Calzolari, (2008) Natural light design for an ancient building: A case study, Journal of Cultural Heritage,