Prelim Analaysis Report Rev0

7/27/2019 Prelim Analaysis Report Rev0

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Pusat Sains Negara

Preliminary Study Report

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Introduction

The study focuses on two factors that currently facing by the occupants as well as visitors in the

atrium of Pusat Sains Negara (PSN), namely thermal comfort and visual comfort. The current

cooling design in the atrium adopted stratification techniques where supply cooled air is directly

dumped to the centre of atrium. Through stratification phenomena, the lighter hot air will rise until

the top of the atrium. However, no venting mechanism is provided at the top of atrium, hence heat

is trapped at the upper space. The hot effect will first be felt at the upper floor and subsequently to

lower floor until the ground floor.

Figure 1: Photo showing ring-ducted supply air grilles dumping cool air to the centre of atrium

On the other hand, visual comfort arises due to both continuously-changing indoor illuminance

level and glare issues in the atrium. Indoor illuminance level is uncontrollable where it is greatly

depending on the outdoor factors such as sun-movement and cloud coverage while glare issues

arises due to a great illuminance contrast as shown in the Figure 3.

As seen from the Figure 3, the glare sources are mostly

spotted at the polycarbonate glass where the shading

device is not installed.

Figure 2: Shading device installed

behind the polycarbonate glass.


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Figure 3: Photo showing glare source (highlighted in blue color)

Preliminary Study

A simple model is built up based on the JPEG drawing and indicative scale. Due to complexity of

the atrium dome structure and absent of detail construction drawing, the dome is modelled with

triangular mesh where the sizes and shapes are not following exactly the actual dome structure.

However, for preliminary study, it is more than enough to analyse the building.

1.0 Sun Movement

The orientation of the building is not critical as the building shape is round. The entrance of the

building is directed to South facing Securities Commission Malaysia (SC). Both Figure 4 and

Figure 5 show the imposed sun-path on the building and model.


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Figure 4: Sun-path overlaid on Goole Maps (Left) and mode (Right)

Figure 5: PSN model with sun-path


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Figure 6: Direct and diffuse solar stress on ground floor

2.0 Insolation (Incident Solar Radiation)

In the analysis, the incident solar radiation impinges on the surface of the model is studied toidentify the location where the most heat is coming into the building through envelope. As seen in

Figure 6, the top of the atrium dome is receiving most heat comparing to the other portion. Its

interesting to note that the incident radiation intensity diminishes as moving outward from the

centre of the circle as shown in Figure 7. The phenomena can be explained when sunlight strikes on

the earth at lower angle (sun closer to horizon), the energy of sunlight spreads over a larger surface

area, and is therefore weaker than if the sun is direct overhead and energy is concentrated on a

smaller area.


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Figure 6: Isolation distribution thoughout the model outmost surfaces

Figure 7: Insolation distribution through the atrium dome (Insolation intensity diminishes as

moving outward from centre)


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3.0 Daylighting

Based on current condition of the polycarbonate glass of dome, it is difficult to know the properties

of the glass as there are deposition and dust covering over the surfaces. So, a typical polycarbonate

is assumed and is given in Figure 8.

Figure 8: Polycarbonate glass properties

A daylight analysis is performed to compare the dome without shading device and with shading

device. The design of shading device is based on the outcome of insolation analysis that is to block

the direct overhead sunlight while allowing diffuse light to go into building. Some important

parameters are given as follows:-

- Testing sky condition: Overcast sky (18,500 lux)

- Grid line position: 800mm from the finished floor level of atrium

Figure 9: Shading device on top of dome


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The result is given Figure 10 and Figure 11 as following:-

Figure 10: Daylight distribution w/o shading device

Figure 11: Daylight distribution c/w shading device

From the result, it can be seen that the daylight intensity is reduced by almost 50%. However, such

high intensity of illuminance level is considered relatively high comparing with the

recommendation specified in MS1525.


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Conclusion & Recommendation

From the preliminary study and site walk, it can be concluded as following:-

- Glare is fairly addressable with the internal blind or shading device. However, only part of

the glass is covered, hence, glare source is still presence. Internal blind can be installed toreduce glare sources.

-

Heat gain to the building is still considerable high because of the large area of glass

although polycarbonate glass has thermal properties on par with typical low-E glass. Heat

gain to the building can only be reduced with the external shading devices or better

performance glass such as double glazing glass.

-

Sun path showing that orientation of building has no effects to the solar heat gain of the

building.

- Insolation analysis proposes that the top part of dome receiving more solar heat than the

bottom part of the dome. Thus, external shading devices can be considered to cover the top

of dome to block direct overhead sunlight while allowing diffuse light to goes into the

building.

-

Further to the daylight analysis, the glass with lower shading coefficient can be selected to

better tune down the daylight intensity to the recommendation level. Complementary

dimmable artificial light with sensors can be considered to produce better illuminance

distribution level.

Prelim Analaysis Report Rev0

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