How to Choose Polycarbonate Sheets for Skylight Glazing

Choose the polycarbonate sheet considering the location and characteristics of your skylight.

Polycarbonate plastics with their lightweight, impact-resistant nature, offer a viable alternative to glass for skylight applications. These plastic sheets are layered with thin coatings that render them resistant to ultraviolet radiation; this, along with a recyclable nature, makes polycarbonate sheets a "green" component of your building. The sheets have a light-diffusing property that renders dirt undetectable; however, they can easily be cleaned by a simple pressurized jet of water. To choose the right polycarbonate sheet, you will have to consider the specific location and characteristics of your skylight.

Instructions

1. Look for abrasion and impact resistance. Polycarbonate sheets are naturally resistant to abrasion as compared to glass. This abrasion resistance can be further increased by applying special top coatings. The thickness of the sheet is a determinant of the amount of impact resistance. The greater the thickness, the better is the ability to resist impact. If you live in an area prone to hailstorms, choose a thicker polycarbonate sheet that has been coated with special materials. Generally, 8 mm sheets are used in cases where the skylight will not encounter wind and water, whereas 25 mm sheets are indicated for exterior applications.

2. Consider the place where you are planning to fit the skylight. If it is to be located in the bathroom or on a greenhouse, choose polycarbonate sheets that have anti-drip or anti-fog coating. This will prevent condensation from dripping back into the bathroom or onto the plants in the greenhouse.

3. Check visible light transmittance (VLT) ratings. Polycarbonate sheets have wide-ranging VLT values. The VLT rating is an indication of the amount of visible light the skylight transmits. If you need lot of natural light coming in, as in a classroom, for instance, choose a clear polycarbonate sheet that has a higher VLT value. Bronze or opal tinted glazing has lower VLT ratings; select this for locations where you require muted lighting.

4. Examine special requirements. Polycarbonate sheets are available as monolithic or multiwall sheets. The multiwall variety has multiple layers that can be filled with an aerogel material. This type of filling makes the sheets more lightweight, insulating and soundproof. Choose this type of polycarbonate if these characteristics are important to your application -- hospitals and classrooms, for example. Select textured polycarbonate sheets if you wish to prevent see-through vision.

5. Consider U-value. The amount of heat flowing through a skylight in either direction is measured as U-value. The lower this rating, the better is the skylight's ability to retain heat and resist heat loss. If you live in areas where winters are harsh, choose a polycarbonate system made up of double polycarbonate panels with an air gap in between. Such sheets have U-values as low as 0.16 and provide high insulation against heat loss.

Tips & Warnings

• Polycarbonate sheets generally are available in blue, green and brown. Choose the color depending on the aesthetics you desire. Remember that the amount of light transmitted will change with the color.

• Polycarbonate sheets of 2 mm thickness are preferred for industrial skylighting.

References

• Green Buildings Solutions: Cellular Polycarbonate Glazing
• Polycarbonate Sheets: Polycarbonate Roof Vent Installation Guide
• American Architectural Manufacturers' Association: Glass or Plastic: The Question for Skylights
• Flexituff Industries: Comparison of Polycarbonate Sheets with Conventional Materials
• Home Tips: Skylights: Ratings for Energy & Light
• Solar Innovations: Polycarbonate Products