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Physical Properties

Light Transmission
The sunlight which reaches the surface of the earth has a wavelength that ranges between 295 - 2140 nanometers (10-9 meters). This wavelength range is divided into the following sections:

UV-B Middle ultraviolet region 280 - 315 nm
UV-A Near ultraviolet region 315 - 380 nm
Visible light region 380 - 780 nm
Near infra-red region 780 - 1400 nm
Middle infra-red region 1400 - 3000 nm

As shown in the Figure below, Multiwall PC sheet has the maximum transmission in the visible light region.

Despite transmitting visible light very well, Multiwall PC sheet is almost opaque to radiation in the UV and far infra-red region. This useful shielding property can prevent discoloration of sensitive materials such as fabrics or other organic materials placed under or behind UV protected PC sheet glazing: e.g. a factory warehouse, museum or shopping center., exterior and interior partitions.

Fig. 5

Temperature Increase Inside the Building
The same properties, in combination with the insulating multiwall structure, contribute to a temperature increase inside the building. Sunlight entering the building heats the air both directly and through absorption by framework, furniture etc., and is released as infra-red energy. The insulating properties of Multiwall PC sheet prevents this heat from escaping faster than it is created, causing a temperature increase - the so-called 'greenhouse effect'. The temperature can be controlled by venting often in combination with specialty solar control sheet like Polygal's Polycoolite.

Solar Control
Transparent grades of Multiwall PC sheet have excellent light transmission, between 64 and 82% depending upon thickness. However, for buildings in hot climates or with south facing aspects, Multiwall PC sheet is available in solar control grades of , solar control grey, blue, green and opal white. These grades significantly reduce solar heat build up, helping to maintain comfortable interior temperatures.

The specially tinted and non-glare sheet cuts down the brightness of sunlight to a pleasing level and reduces air conditioning costs in the summer.

Solar Heat Gain
The solar radiation reaching the sheet is reflected, absorbed and transmitted, as shown in Figure 6. The greatest proportion is transmitted and the total solar transmission (ST) is the sum of the direct transmission (DT) and the inwardly released part of the absorbed energy (A). Table 7 outlines the overall solar control properties of the Multiwall PC sheet .

Fig. 6


Fig. 7  Compare by dividing Light transmission/Solar Transmission. The higher the value, the better the control of solar heat gain.

Total Solar Transmission (ST) in %
Material TW6
2RS
TW8
2RS
TW10
2RS
TW16
3TS
TW16
2NS
TW16
4RS
TW20
5RS
Clear 112 86 86 85 82 82 80 75
Bronze

5109
51914
515055

60

55

60
35

60



55



55



55



55
White
825074
825075
82995

50
30
76

50
30


30



71



71



71



65

 

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Polycoolite is a registered Trademark of Polygal Inc.

 

 

This page was last modified on April 26, 2010 

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