Selectivity in Tropical Countries

Light Transmission needs to be optimized so as to avoid glare and minimize artificial illumination. It mainly depends on use of buildings. Retail / shopping areas may require maximizing light transmission due to higher visibility whereas software parks may require minimizing light transmission to reduce glare.

Glass needs to transmit true colour, which means the colour of light transmitted through the glass should be close to that of light through the clear glass. This is essential to avoid false lighting and giving a perfect working atmosphere.

Solar control by body-tinted glass is due to its absorption property of heat. They are also know as heat absorbing glasses and provide medium level of solar control.

Solar control by reflective glasses is due reflection of solar energy and produce very good solar control. It is most effective on sun facing wall. The optimum position of solar control coating is on external surface of the building. All hard coatings are durable for this application. Soft and medium solar coating cannot be positioned on external surfaces.

Body tinted glasses with reflective coatings achieve solar control by absorbing as well as reflecting solar heat energy. They combine both the functions. Reflective glass is best for reducing peak air-conditioning load requirements. Double glazed or insulating glass unit helps in further reducing the operating costs. Saving in capital and operating costs of AC is best achieved by using a double glazing with solar control coated glass on the outside with clear or low e glass on the inside.

Any solar control product, however selective in its absorption or reflection of solar radiation, will reduce the light transmission. Though ultraviolet constitutes only 3% of the solar spectrum, it is the major cause of fading curtains, carpets and upholstery inside a building. Laminated glass cuts down almost 99% of all ultraviolet radiation and drastically reduces fading.

Indicative values of the factors determining the performance of glass (photometric properties) with respect to the glass type covered in the study are annexed in table 3.1 to 3.9.

Table 3.1 : Normal (Annealed) Glass (Clear Glass - Photometric Properties)

Thick

U value

UV

Visible Light

Solar Energy

ness

(Watts / sq.m. k)

Transmitt

Transmit

Reflectance

Reflectance

Transmit

Shading

(mm)

ance %

tance

Indoor

Outdoor

(Out)

-tance

Coefficient

2

3.53

77

90

8.1

8.1

7.6

86

1.00

3

3.53

72

90

8.0

8.0

7.4

83

0.99

4

3.47

67

89

7.9

8.0

7.2

80

0.97

5

3.44

64

88

7.9

7.9

7.0

77

0.95

6

3.44

61

87

7.8

7.8

6.9

75

0.93

8

3.37

56

86

7.7

7.7

6.6

70

0.89

10

3.34

52

85

7.6

7.6

6.4

66

0.86

12

3.28

49

83

7.5

7.5

6.2

62

0.83

15

3.22

44

81

7.3

7.4

6.9

57

0.80

19

3.15

39

78

7.1

7.2

5.7

51

0.75

Laminated Annealed Glass
Table 3.2 : Normal (Annealed) Glass (Bronze - Photometric Properties)

Thickness (mm)

U value

(Watts 1 sq.m. k)

UV Transmit-tance %

Visible Light

Solar Energy

Transmit -tance

Reflectance

Reflectance (Out)

Transm it-tance

Shading Coefficient

Indoor

Outdoor

3

3.47

36

66

6.3

6.5

6.3

64

0.85

4

3.47

28

58

5.9

6.1

5.9

57

0.79

5

3.44

22

52

5.5

5.7

5.6

51

0.74

6

3.44

18

46

5.3

5.5

5.3

45

0.70

8

3.37

12

37

4.9

5.1

5.0

36

0.63

10

3.34

08

29

4.6

4.9

4.8

29

0.57

12

3.28

5

23

4.5

4.8

4.7

23

0.53

Table 3.3 : Normal (Annealed) Glass (Grey - Photometric Properties)

Thickness (mm)

U value

(Watts / sq.m. k)

UV Transm it-tan ce %

Visible Light

Solar Energy

Transmit-tance

Reflectance

Reflectance (Out)

Transm it-tance

Shading Coefficient

Indoor

Outdoor

3

3.50

37

62

6.2

6.4

6.3

63

0.83

4

3.47

29

55

5.8

6.0

5.9

55

0.77

5

3.44

23

48

5.4

5.7

5.6

49

0.72

6

3.44

19

42

5.1

5.4

5.4

43

0.68

8

3.37

13

32

4.8

5.1

5.1

34

0.61

10

3.34

09

25

4.6

4.9

4.9

26

0.55

12

3.28

06

19

4.4

4.8

4.7

21

0.51

Table 3.4 : Laminated Glass (Photometric Properties)

Transm ittance [%]

Transmittance [%]

Shading Coefficient

Ratio of VLT/UVT

U Value [Watts/sq m.°K]

Laminated Glass for 6 mm thickness

Clear

89

77

0.92

1.16

1.05

Blue Green

73

68

0.84

1.07

Translucent White

65

58

0.76

1.12

1. Light bronze

52

54

0.72

0.96

2. Medium bronze

28

34

0.56

0.82

Grey

44

47

0.67

0.94

Blue Grey

28

39

0.60

0.72

Laminated Insulating Gla

3 mm thick

Clear

79

62

0.78

1.27

0.50

Blue Green

66

56

0.72

1.18

Bronze [light]

46

43

0.60

1.07

Neutral Brown flight!

49

44

0.63

1.11

Laminated Insulating Glass 6 mm thick

Grey

39

36

0.54 j

1.08

0.46

Translucent White

58

45 0.63

1.29

Table 3.5 : Mirror (Photometric Properties)

Thick ness (mm)

U value

{Watts/ k} -

Transmit tance %

Transmit -tance

Reflectance

Reflectance

¡¡Sllill

>olar Energy Transmitt -ance

Shading Coefficient

indoor

)utdoo

6.3

3.53

0

0

93

0

0

0

0.35

5.9

3.50

0

0

92

0

0

0

0.36

5.6

3.47

0

0

90

0

0

0

0.36

5.4

3.47

0

0

89

0

0

0

0.36

5.1

3.44

0

0

87

0

0

0

0.36

Table 3.6 : Reflective Single Glazing (6 mm Thickness - Photometric Properties)

Description

Coating

U

Visible Light

Solar Energy

value

Trans

Reflectance

Reflec

Transmit

Shading

(Watts /

mittan

Indoor

Outdooi

tance

tance

Coefficient

sq.m. k)

ce

(Out)

Silver

SS - 8

2.84

8

37

41

34

7

0.23

SS - 14

2.96

14

35

31

27

11

0.30

SS - 20

3 .12

20

32

25

22

16

0.37

Sterling

CS - 14

2.90

14

37

33

27

12

0.30

CS - 20

3 .00

20

32

27

22

17

0.37

Silver-Blue

TS - 20

3 .00

20

33

23

22

14

0.35

Blue

TS - 30

3 .15

30

29

17

15

24

0.46

Deep-Blue

TS - 40

3 .37

40

24

10

10

32

0.55

Green

S - 8

2.84

6

37

34

19

4

0.25

SS -14

2.96

11

35

27

16

6

0.29

SS -20

3 .12

16

32

20

13

9

0.34

Blue Green

TS -20

3.00

17

33

18

12

9

0.34

TS -30

3 .15

26

29

14

9

15

0.40

Bronze

SS - 8

2.84

5

37

17

15

4

0.26

SS -14

2.96

8

35

15

13

6

0.30

SS -20

3 .12

12

32

12

11

10

0.35

Grey

SS - 8

2.84

4

37

13

15

4

0.26

SS -14

2.96

7

35

10

12

6

0.31

SS -20

3 .12

10

32

9

10

9

0.35

Silver Blue

TS -20

3 .00

10

33

9

11

8

0.33

Grey

Sapphire

TS -30

3 .15

15

28

7

8

14

0.40

Blue-Grey

Table 3.7 : Reflective Double Glazing (25 mm - Photometric Properties)

Descrip

Coating

U value

Visible Light

Solar Energy

tion

(Watts / sq.m. k)

Transmit-

Reflectance

Reflect

Transmit-

Shading

tance

Indoor

Outdoor

ance (Out)

tance

Coefficient

Silver

SS - 8

1.26

7

38

41

34

6

0.16

SS - 14

1.32

13

37

31

27

9

0.21

SS - 20

1.39

18

34

25

22

13

0.27

Sterling

CS - 14

1.29

13

38

33

28

10

0.22

CS - 20

1.32

18

34

27

23

15

0.28

Silver-

TS - 20

1.39

18

35

23

22

12

0.25

Blue

Blue

TS - 30

1.42

27

31

17

15

20

0.35

Deep-Blue

TS - 40

1.48

36

27

11

10

20

0.35

Green

SS - 8

1.26

5

38

34

19

3

0.15

SS - 14

1.32

10

37

27

16

5

0.18

SS - 20

1.39

15

34

20

13

8

0.22

Blue

TS - 20

1.39

16

34

18

12

8

0.23

Green

TS - 30

1.42

23

31

14

9

13

0.28

Bronze

SS - 8

1.26

4

38

17

15

3

0.16

SS - 14

1.32

7

37

15

13

5

0.19

SS - 20

1.39

11

34

12

11

8

0.23

Grey

SS - 8

1.26

4

38

13

15

3

0.16

SS - 14

1.32

6

37

10

11

5

0.19

SS - 20

1.39

9

34

9

10

8

0.23

Silver

TS - 20

1.39

9

34

9

11

7

0.22

Blue Grey

Sapphire

TS - 30

1.42

13

31

7

8

12

0.28

Blue-Grey

Table 3.8 : Reflective Glass (6 mm Thickness - Photometric Properties)

Description

(Watts I sq.m. k)

Visible Light

Solar Energy

Transmit-tance

Reflectance

Reflectance (Out)

Transmit-tance

Shading Coefficient

Indoor

Outdoor

Harvest Bronze

CB - B

2.B4

5

55

13

13

4

0.27

CB - 14

3.03

B

50

10

10

B

0.33

CB - 20

3.22

12

44

B

8

11

0.38

Misty Bronze

CP - B

2.B7

5

53

14

13

4

0.27

CP - 14

3.12

B

47

11

10

B

0.34

CP - 20

3.22

12

41

10

9

12

0.38

Charren Gray

CB - B

2.B4

4

55

10

12

4

0.27

CB - 14

3.03

7

50

B

10

B

0.33

CB - 20

3.22

10

44

7

8

11

0.38

Misty Gray

CP - B

2.B7

4

53

11

13

4

0.28

CP - 14

3.12

7

47

9

10

B

0.34

CP - 20

3.22

10

41

B

8

12

0.38

Royal Indigo Gray

CR - B

2.B1

4

55

9

11

5

0.28

CR - 14

3.00

7

50

B

8

B

0.33

CR - 20

3.19

10

44

6

7

11

0.38

Platinum

SP - 13

2.93

13

43

29

23

12

0.31

SP - 1B

3.06

1B

3B

24

21

16

0.36

SP - 22

3.12

22

36

19

17

20

0.41

SP - 33

3.25

33

27

11

10

29

0.52

Serenity Green

SP - 13

3.06

11

43

23

13

7

0.31

SP - 1B

3.12

15

3B

19

12

10

0.34

SP - 22

3.25

19

36

15

10

12

0.37

SP - 33

2.93

2B

27

9

7

1B

0.44

Satin Bronze

SP - 13

3.06

B

43

10

11

7

0.31

SP - 1B

3.12

11

3B

9

11

10

0.34

SP - 22

3.25

13

35

B

9

12

0.37

SP - 33

2.93

20

27

6

6

1B

0.44

Starlite Gray

SP - 13

3.06

7

43

10

11

7

0.31

SP - 1B

3.12

9

3B

9

10

10

0.34

SP - 22

3.25

11

35

B

9

12

0.37

SP - 33

2.B4

16

27

6

6

1B

0.44

Non-Coated Glass

Clear Normal

3.56

B9

B

B

7

B1

0.96

Clear Laminated

3.37

B6

7

7

6

67

0.B6

Green Tint

3.56

76

7

7

6

4B

0.71

Bronze

3.56

53

6

6

5

4B

0.70

Grey

3.56

43

5

5

5

47

0.70

Table 3. 9 : Insulating Glass (Photometric Properties)

Description

Nominal Thickness, mm

U value 6 mm air space

U value 12.9 mm air

space

Visible Light Transmission %

Solar Radiant Heat Reflection %

Solar Radiant Heat Absorption %

Direct Solar Transmission %

Total Solar Transmission %

Shading Coefficient

No Shade

Shading Coefficient Venetian Blinds -Light

Shading Coefficient Venetian Blinds -Medium

Shading Coefficient

Drapes - Light

Shading Coefficient

Drapes - Medium

Clear Normal & Monolithic

6

1.13

1.13

87

8

12

80

84

0.95

0.55

0.64

0.56

0.61

Clear Normal & Clear Normal

6

0.64

0.56

76

13

23

64

73

0.83

0.51

0.57

0.48

0.53

Clear Normal & Bronze Normal

6

0.64

0.56

44

7

58

35

46

0.52

0.36

0.39

0.38

0.41

Clear Normal & Grey Normal

6

0.64

0.56

37

7

58

35

46

0.52

0.36

0.39

0.38

0.41

Clear Normal & Green Normal

6

0.64

0.56

43

13

42

45

55

0.62

0.43

0.46

0.46

0.49

Solar Panel Basics

Solar Panel Basics

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