# Switchable Smart Glass — PDLC and Electrochromic

> Switchable smart glass is glass laminated with an electrically switchable film. PDLC switches almost instantly between clear and opaque for privacy on interior partitions, while electrochromic glass tints gradually to control solar gain and glare on exterior facades; the two solve different problems and are not interchangeable.

## What it is

Glass laminated with an **electrically switchable film**. Two distinct
technologies sit under the label, and they do different jobs.

| | PDLC | Electrochromic |
| --- | --- | --- |
| Switches | Clear ↔ opaque | Clear ↔ tinted |
| Speed | Near instant | Minutes |
| Purpose | Privacy | Solar and glare control |
| Typical use | Interior partitions | Exterior facade glazing |
| Opacity | Fully obscuring | Never fully opaque |

## What the specification must cover

Because this is glass **and** an electrical installation, both sides need
defining:

- Panel sizes and the maximum size the film is available in
- **Power supply location** and the concealed cable route to each panel
- Switching method — wall switch, BMS, occupancy sensor, app
- Failure state: what the glass does when power is lost
- Edge detail, since the busbar and wiring must be concealed within the frame
- Safety classification of the laminated build-up to IS 2553 (Part 1)

The wiring is the part that gets missed. A switchable panel needs a cable to it,
and that route has to be designed into the partition head or the floor before
anything is built.

## Where projects go wrong

- **Specified late**, after partitions are designed with no cable route.
- **Power failure state not considered**, so a boardroom goes opaque in an
  outage, or a facade sticks clear during peak sun.
- **Expecting solar control from PDLC.** It does not deliver it.
- **Panel size exceeding film width**, forcing a joint the architect did not
  expect.
- **No isolation or maintenance access** to the driver and transformer.

## Standards referenced

Architectural safety glass to **IS 2553 (Part 1)**. Fenestration provisions
under **ECBC 2017**. Electrical installation practice under **IS 732**.

## Frequently asked questions

### What is the difference between PDLC and electrochromic glass?

PDLC switches between clear and opaque for privacy, almost instantly, and is used on interior partitions. It does very little for solar heat. Electrochromic glass tints gradually over several minutes to control solar gain and glare on an exterior facade, and it never becomes fully opaque. They solve different problems and are not interchangeable.

### Does PDLC glass need power all the time?

Standard PDLC is clear when powered and opaque when off, so a meeting room left clear draws power continuously through the working day. Consumption per square metre is low but not zero, and the failure mode matters: a power cut makes the glass opaque. Reverse-mode products exist where the default is clear, and the choice should be made deliberately against how the room is used.

### Is switchable glass worth the cost?

In specific places. A boardroom or a director's office where privacy is needed on demand without blinds justifies it, as does a medical consulting room. Across a whole floor of meeting rooms it rarely does, because acid etched glass or a blind achieves most of the benefit for a fraction of the cost. Treat it as a feature specification, not a default.

## Sources

- [IS 2553 (Part 1)](https://standards.bis.gov.in/website/published-standards/department-wise) — Safety glass — architectural
- [ECBC 2017](https://beeindia.gov.in/) — Building envelope — fenestration
- [IS 732](https://standards.bis.gov.in/website/published-standards/department-wise) — Code of practice for electrical wiring installations

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Source: https://hagerstone.com/materials/switchable-smart-glass