SmartGlass wiring through a double-stud wall: the electrical coordination architects forget on a home-office partition

A 2.8-metre frameless partition dividing a master bedroom into bedroom and office in Indiranagar last month. The glass was specified at 10mm toughened, the frame in anodised aluminium, the partition itself structural. But the switchable glass—the Studio partition system—required a 230V single-phase supply at 16A, routed through the stud cavity, and the architect's electrical consultant had not been in the room when the partition was dimensioned.

The result: a site coordination meeting at week 8, a revised shop drawing, and three days of rework. The partition itself was sound. The wiring was not.

This is a note on what to specify, and when, so the glass arrives fitted and live on handover.

Why SmartGlass needs its own electrical brief

Switchable glass—whether privacy film in a bathroom or a full partition system—draws power continuously. The film itself consumes between 3–5 watts per square metre in the opaque state. A 2.8m × 2.2m partition draws roughly 18–22 watts steady-state, plus a brief inrush when the voltage is applied. That is not a lighting circuit. It is not a plug load. It is a dedicated supply, and it must be routed before the stud wall is closed.

The electrical rough-in for a SmartGlass partition is not incidental. It is structural coordination. If the conduit is not run during framing, it cannot be run after. If it is run in the wrong location, it conflicts with the glass frame itself, and either the frame is relocated (site tolerance issue) or the conduit is rerouted (cost and delay).

Routing the supply: conduit sizing and path

Conduit diameter and voltage drop

For a single-phase 16A supply to a SmartGlass partition, specify a 20mm (3/4-inch) PVC conduit. This allows 2.5mm² copper twin-and-earth cable with a 1.5mm² earth, or a single 4mm² + 4mm² + 1.5mm² sheathed cable. Do not undersize to 16mm conduit; the cable will not draw through without damage to the sheath, and the contractor will cut the sheath on site to force it.

Voltage drop over 8 metres of cable run (typical for a partition in the centre of a bedroom in HSR Layout or Koramangala) is 1.2–1.6 volts on a 230V supply using 2.5mm² copper. This is within tolerance (3% of 230V = 6.9V). If your run exceeds 12 metres—say, from a distant sub-board in a Whitefield villa—specify 4mm² cable and recalculate. Voltage drop at the glass itself must not fall below 220V, or the switching response will be sluggish and the warranty is void.

Path through the stud cavity

The conduit must run vertically through the double-stud wall cavity, not horizontally. Horizontal runs collect water during the monsoon months (June to September), and the hard water from Cauvery supply (TDS 200–300 ppm) leaves mineral deposits inside the conduit. Over two years, this can corrode the cable sheath.

Specify the conduit entry point 150mm above the finished floor level. This clears the toe-kick and any future skirting board. The exit point—where the conduit emerges into the glass frame's electrical housing—must be dimensioned to the millimetre on the shop drawing. The glass frame has a 25mm-deep electrical cavity cast into the aluminium section. If the conduit exits 30mm above the cavity, the cable will not reach. If it exits 20mm below, it will kink inside the frame.

The shop drawing: glass frame and conduit coordination

This is where the architect and the electrical consultant must speak to each other before the shop drawing is issued.

The glass frame for a SmartGlass partition is manufactured with a pre-cast electrical terminal box, typically 80mm × 60mm × 40mm deep, located at the base of one vertical stile. This box has two knockouts: one for the incoming supply, one for the outgoing control wire (if a wireless control module is not used). The knockouts are 20mm diameter.

On the shop drawing, the frame manufacturer will show the location of this box relative to the floor, the glass edge, and the partition's anchor points. The electrical consultant must then overlay the conduit route onto this drawing and confirm that the conduit emerges within 100mm of the box. If the partition is positioned 300mm from an existing wall (to allow a skirting board or a radiator), and the sub-board is on the opposite wall, the conduit route may not be straight. It may need to step through the stud cavity, adding 0.5–1 metre to the run length. Recalculate voltage drop.

Issue the coordinated shop drawing to the contractor and the electrician together. Do not send the glass drawing to the glazier and the electrical drawing to the electrical contractor separately. They will interpret the floor plan differently, and the conduit will be in the wrong place.

On site: the coordination meeting at week 6

Schedule a site meeting with the architect, the electrical contractor, and the glass fitter before the stud wall is closed. Bring a measuring tape, a level, and a 20mm conduit offcut. Walk through the exact path of the conduit from the sub-board to the partition location. Mark the stud cavity with tape at the entry and exit points. Have the electrical contractor run a draw-wire through the conduit immediately—do not wait until the wall is closed.

Check for obstructions: cross-bracing in the stud cavity, plumbing runs, or HVAC ducts. In a Sarjapur Road villa with a central return-air duct, the conduit may need to drop 300mm lower to clear the duct. This changes the exit point on the glass frame. Update the shop drawing and issue a revision before the frame is cut.

Confirm the finished floor level (FFL) with the contractor. If the FFL is 50mm higher than the architect's drawing shows, the conduit entry point—specified at 150mm above FFL—will be in the wrong location. Mark the actual FFL on the site plan before the electrical work begins.

The handover: testing and commissioning

When the partition is installed and the conduit is connected, the electrician must test the supply voltage at the glass frame's terminal box before the glass is powered. Voltage must be between 220V and 240V. If it is below 220V, the cable is undersized or the run is too long. Do not energise the glass. Rework the cable or the route.

Once the voltage is confirmed, the glass fitter will connect the film's power terminals to the incoming supply and test the switching response. The glass should transition from clear to opaque in 3–5 seconds. If the transition is slow or the glass does not fully opaque, the voltage is marginal. This is a sign that the electrical specification was not followed on site.

Document the voltage reading and the switching time on the handover certificate. If a defect emerges after handover—slow switching, intermittent opacity—the electrical supply is the first thing to check, and the test certificate proves whether the voltage was correct at commissioning.

Questions we get asked

Can we run the conduit through the partition frame itself, instead of through the wall?

No. The partition frame is aluminium and is anodised for corrosion resistance. Running a live conduit through it creates a risk of electrical leakage into the frame, and the anodising will be damaged during installation. The conduit must be in the stud cavity, separate from the glass frame, and connected to the frame's terminal box via a 150mm flex connector at the base.

What if the partition is non-structural—just a divider, not load-bearing?

The electrical requirement does not change. Non-structural partitions are often single-stud or aluminium-framed, with thinner cavities. If the cavity is less than 50mm deep, you cannot fit a 20mm conduit. Specify a surface-mounted conduit instead, routed along the base of the partition and boxed in with a matching aluminium trim. This adds 40–60mm to the partition's footprint and must be drawn on the floor plan.

Can we use wireless control instead of a hardwired supply?

The glass film itself still needs power. Wireless control removes the control-wire run (the secondary circuit), but the main 16A supply must still be hardwired. A wireless module sits in the electrical cavity and communicates with a remote or a mobile app, but the power to the film is always mains-fed. There is no battery option for SmartGlass partitions in residential installations.

What happens if the site dimensions don't match the shop drawing?

The partition dimensions change, and the conduit route must be recalculated. This is why the site meeting at week 6 is essential. If the partition is 200mm further from the sub-board than the drawing shows, the conduit run is 200mm longer, and voltage drop increases. If the conduit route has to step around an obstruction, the run can be 1 metre longer. In either case, the electrical consultant must recalculate and confirm that voltage at the glass frame will still be above 220V. If it will not be, the cable gauge must be increased (4mm² instead of 2.5mm²), or a separate sub-board must be installed closer to the partition. Do not proceed without this confirmation in writing.

Who is responsible if the glass doesn't switch properly after handover?

The electrical supply voltage is the responsibility of the electrical contractor and the consultant who specified it. The glass film's response is the responsibility of the glass fitter and the manufacturer. If the switching is slow, the first test is the voltage at the terminal box. If the voltage is correct (220V–240V) and the switching is still slow, the film is faulty and the manufacturer must replace it. If the voltage is below 220V, the electrical contractor must rework the supply. This is why the handover test certificate is critical—it proves which party is responsible.

If you are coordinating a SmartGlass partition for a Bangalore home-office project, the electrical brief is not an afterthought. It is part of the partition specification. Bring the electrical consultant into the room when the partition is dimensioned, and issue a coordinated shop drawing before the stud wall is framed. The cost of coordination is a day of meetings. The cost of rework is three days on site and a delayed handover. Talk to the atelier about your partition specification, and we will walk you through the electrical coordination on your project.