# Polycarbonate Skylight Sheet for Industrial Roofs

> Polycarbonate skylight sheet is translucent polycarbonate, solid profiled or multiwall, matched to the surrounding metal roof sheet to bring daylight into industrial and warehouse spaces. Its service life depends on the co-extruded UV-protected face being installed upward, and skylight area trades lighting savings against solar heat gain.

## What it is

Translucent **polycarbonate sheet**, profiled to match the metal roof sheet
around it, used to bring daylight into a large industrial or warehouse space
without electric lighting.

## Specification at a glance

| Property | Typical specification |
| --- | --- |
| Type | Solid profiled, or multiwall |
| Thickness | 1.5mm — 3mm profiled; 6mm — 25mm multiwall |
| UV protection | Co-extruded layer, one or both faces |
| Light transmission | Specified as a percentage |
| Profile | Matched to the adjacent metal sheet |
| Fire class | Named EN 13501-1 class |

## Solid profiled against multiwall

| | Solid profiled | Multiwall |
| --- | --- | --- |
| Insulation | Poor | Better, sealed air cells |
| Light quality | Clear, higher transmission | Diffused, softer |
| Strength | Good impact resistance | Good, lighter |
| Detailing | Laps like the metal sheet | Needs sealed edge tapes |
| Use | Standard industrial roof lights | Conditioned or diffused-light spaces |

## The daylight and heat trade-off

Roof lights cut lighting load — and that saving works against the ECBC lighting
power density target — but they also admit solar heat directly onto the working
floor. In an air-conditioned building that heat becomes cooling load.

The practical answer on most Indian industrial roofs is a **modest percentage
of roof area**, distributed evenly for uniform light rather than concentrated,
with diffusing multiwall used where glare on a working plane matters.

## Where projects go wrong

- **UV face installed downward.** The single most common and most damaging
  error.
- **Too much skylight area**, turning a lighting saving into a cooling cost.
- **Fixings through the sheet without oversized holes.** Polycarbonate expands
  considerably more than steel; pinned sheets crack around the screws.
- **Edges of multiwall left unsealed**, so dust and moisture enter the cells and
  the sheet clouds permanently.
- **Walking on roof lights.** They are not a walking surface; many industrial
  roof falls happen through them.

## Standards referenced

Skylight and daylighting provisions under **ECBC 2017**. Wind loading under
**IS 875 (Part 3)**. Reaction-to-fire classification to **EN 13501-1**.

## Frequently asked questions

### How much of an industrial roof should be skylight?

Commonly 3 to 5 percent of roof area, and ECBC 2017 sets limits alongside daylighting provisions. More than that and solar heat gain starts to outweigh the lighting benefit, especially in Indian conditions where the roof takes intense sun for most of the day. The right figure depends on internal working plane requirements and whether the space is air conditioned.

### Which face must point upward?

The UV-protected face, which is marked on the protective film. Polycarbonate degrades rapidly under direct ultraviolet, so the co-extruded UV layer is what gives the sheet its service life. Installing a sheet upside down is an easy site error, it is invisible on the day, and it yellows and embrittles within a couple of seasons.

### Is polycarbonate or FRP better for roof lights?

Polycarbonate has far higher impact resistance and better long-term clarity, so it is the safer choice where anything might fall on the roof or where people access it. FRP is cheaper and more rigid but yellows and can become brittle with age. For a building with a long design life, polycarbonate with a proper UV layer is usually the better investment.

## Sources

- [ECBC 2017](https://beeindia.gov.in/) — Building envelope — skylights and daylighting
- [IS 875 (Part 3)](https://standards.bis.gov.in/website/published-standards/department-wise) — Wind loads — roof cladding
- [EN 13501-1](https://standards.cencenelec.eu/ords/f?p=CEN:105) — Reaction to fire classification

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Source: https://hagerstone.com/materials/polycarbonate-skylight-sheet