study of fritted glass in glare control for mlc

5/22/2018 Study of Fritted Glass in Glare Control for MLC

1

Introduction

Visual discomfort from window is normally due to the glare. Glare is often resulted whenever

there is a huge contrast level within a human field of view, especially during the direct

penetration of sunlight. Sunlight and daylight are distinguishable in the sense that sunlight is

mostly due to direct solar radiation which is least useful to an inhabitable space whereasdaylight is due to diffuse solar radiation. Glare is a very subjective perception of brightness

and contrast in a room or space, depending on individual. As a guide given in MS1525:2013,

the brightness inside a building and the associated distribution can be classified by the

daylight factors as shown in table below:

Table 1: Classification of glare level based on DF (extracted from MS1525:2013)

DF (%) Lighting Glare Thermal Comfort

>6.0 Intolerable Intolerable Uncomfortable

3.5 6.0 Tolerable Uncomfortable Tolerable

1.0 3.5 Acceptable Acceptable Acceptable< 1.0 Perceptible Imperceptible Acceptable

The simplest form of description of the daylight distribution, penetration and intensity is the

Daylight Factor (DF), expressed as a percentage. This is the ratio of the internal illuminance

(Einternal) at a point in a room to the instantaneous external illuminance (Eexternal) on a

horizontal surface:

=

100%

Description of Input

The public circulation or corridor of level 3 (approximate 2,190m2) is simulated for three

scenarios described below:

Scenario East West

Scenario 1 Single Glazing Ceramic Fritted Glass with 50% Coverage



Scenario 4 Single Glazing Single Glazing

The glass properties are summarized as below:

Ceramic Fritted Glass with 50% Coverage



2


U-value SC VLT(%)

Single Glazing 5.8 0.94 92

Single glazing glass

The test reference sky and working plane for analysis is summarized below:

Sky condition : CIE Overcast Sky

Sky illuminance level : 18 klux

Working plane : 800mm above respective floor

Ceiling reflection : 80%

Wall reflection : 60%

Floor reflection : 40%

The faade based on latest 3D-architectural layout is given below:

Western faade


3

Eastern faade


4

Result

Scenario 1: Ceramic fritted glass with 50% coverage

RAD Daylight Factors

Contour Band Within Above

(from-to) Pts (%) Pts (%)

0-0.5 11977 26.64 44952 100

0.5-1 17476 38.88 32975 73.36

1-1.5 3915 8.71 15499 34.48

1.5-2 2230 4.96 11584 25.77

2-2.5 1684 3.75 9354 20.81

2.5-3 1251 2.78 7670 17.06

3-3.5 832 1.85 6419 14.28

3.5-4 538 1.2 5587 12.43

4-4.5 471 1.05 5049 11.23

4.5-5 341 0.76 4578 10.18

5-5.5 331 0.74 4237 9.43

5.5-6 312 0.69 3906 8.69

>6.0 3594 8.00


5





0-0.5 12155 27.04 44952 100

0.5-1 17220 38.31 32797 72.96

1-1.5 4684 10.42 15577 34.65

1.5-2 2436 5.42 10893 24.23

2-2.5 1166 2.59 8457 18.81

2.5-3 1054 2.34 7291 16.22

3-3.5 819 1.82 6237 13.87

3.5-4 568 1.26 5418 12.05

4-4.5 486 1.08 4850 10.79

4.5-5 386 0.86 4364 9.71

5-5.5 450 1.00 3978 8.85

5.5-6 287 0.64 3528 7.85

>6.0 3241 7.21


6





0-0.5 19331 43 44952 100

0.5-1 12732 28.32 25621 57

1-1.5 3582 7.97 12889 28.67

1.5-2 1550 3.45 9307 20.7

2-2.5 1083 2.41 7757 17.26

2.5-3 1093 2.43 6674 14.85

3-3.5 817 1.82 5581 12.42

3.5-4 594 1.32 4764 10.6

4-4.5 542 1.21 4170 9.28

4.5-5 320 0.71 3628 8.07

5-5.5 254 0.57 3308 7.04

5.5-6 257 0.57 3051 6.79>6 2794 6.22


7

Scenario 4: All normal single glaze glass




0-0.5 8899 19.8 44952 100

0.5-1 17319 38.53 36053 80.2

1-1.5 5593 12.44 18734 41.68

1.5-2 2035 4.53 13141 29.23

2-2.5 1264 2.81 11106 24.71

2.5-3 1185 2.64 9842 21.89

3-3.5 920 2.05 8657 19.26

3.5-4 591 1.31 7737 17.21

4-4.5 518 1.15 7146 15.9

4.5-5 344 0.77 6628 14.74

5-5.5 318 0.71 6284 13.98

5.6-6 289 0.64 5933 13.27

>6.0 5644 12.56


8/

Discussion & Conclusion

Its important to note that there are two components that cause glare from windows. They

are direct glare from sunlight and brightness of window due to intense daylight. Firstly, the

direct glare is anticipated to occur at Eastern faade and Western faade as shown in site

plan below with overlaid sun-path.

Assuming the mall operates from 10.00a.m to 10.00p.m. The mall will experience high angle

sunlight from 10.00a.m. until 12.00p.m where sun is directly overhead. At this short period of

time, the direct glare in Eastern faade is minimal. After 12.00p.m., the sun angle will slowly

move to low angle and until sunset. At this period, the Western faade will experience the

sunlight from all angles. Therefore, direct glare from Eastern faade is minimal while

Western faade is critical. The direct glare can only be fully addressed with fins, blinds, or

other shading devices that obstruct the direct penetration of sunlight to the occupants in the

building. The proposed ceramic fritted glass can only partially address the direct glare.Generally, the greater the coverage of ceramic frit pattern, the better the direct glare control.

However, greater coverage will also reduce the useable daylight (DF 1.0~3.5%) that

admitted to the building.

Secondly, the intense of brightness admitted to the building by windows can result in glare.

Daylight factor (DF) is the key indicator for the glare occurrence possibility as described in

the introduction. The sky condition tested in the simulation is CIE overcast sky. CIE overcast

sky resembles to the cloudy sky where illuminance of sky is assumed to be uniformly-

distributed throughout the sky dome. The daylight factor simulation is summarized in table

below:

11.00

13.00

15.00


9/

DF (%)Tolerance

level to glare

Percentage of affected area (%)

Scenario 1(50%

coverage)

Scenario 2(60%

coverage)

Scenario 3(70%

coverage)

Scenario 4(0%

coverage)

>6.0 Intolerable 8.00 7.21 6.22 12.56

3.5 6.0 Uncomfortable 4.44 4.84 4.38 4.581.0 3.5 Acceptable 22.05 22.59 18.08 24.47

< 1.0 Imperceptible 65.52 65.35 71.32 58.33

It can be seen from the table above that the proposed fritted glass in Western faade

reduces affected area of intolerable glare from 12.56% to 8.00% for Scenario 1, 7.21% for

Scenario 2 and 6.22% for Scenario 3. As aforementioned, the greater the coverage

percentage of ceramic frit pattern, the better the glare control, but the lower the usable

daylight admitted through the glass. By comparing between the four scenarios, the 60%

coverage ceramic frit pattern glass or Scenario 2 is preferable over other two options due to

the better glare control while the reduction of usable daylight is insignificant comparing to

Scenario 1.

study of fritted glass in glare control for mlc

Documents

coverageceramic fritted

glare control

classification of glare

daylight distribution

sky condition

corridor of level

floor reflection

huge contrast level