Up to 40% Less Solar Gain from Luxaflex Duette Shades on a West-Facing Lounge

Measuring the Reveal First

Measure the recess in three positions across the width and three down the drop. For width, take readings at the top, middle and bottom. For drop, measure left, centre and right. Reveals are rarely square, especially in older masonry, where a 6mm to 10mm difference between the top and bottom width is common.

A Duette shade has a honeycomb stack, so the ordering width has to respect the tightest part of the opening. If the shade is ordered to the widest reading, the fabric can bind at the narrower point or leave a visible light gap along the side. For a recess fit, most Luxaflex fitters use the smallest of the three width measurements and deduct nothing, because the side channels are intended to sit tight inside the plaster.

Depth carries particular weight on a west elevation. The solar gain benefit depends on the fabric sitting close to the glass and on the air pocket staying sealed at the sides. A reveal depth under 60mm often pushes the installation toward a face fix, which places the fabric farther from the pane and leaves the edges open to convection.

Record depth while taking width and drop. A steel tape gives a steadier result inside a shallow reveal than a laser, because the beam can catch the plaster return and overstate the depth by several millimetres.

What the Honeycomb Cell Does

Duette fabric folds into hexagonal cells that hold a captive column of still air. Still air conducts heat poorly, and that trapped layer is the feature that separates a honeycomb shade from a flat roller fitted across the same window.

Luxaflex sells single-cell and double-cell constructions. The double-cell version adds a second air chamber and carries a higher stated insulation value. In a west-facing lounge the same window has seasonal demands: afternoon solar gain in July and room heat loss through the glass in January.

The up-to-40% solar gain figure is a manufacturer reduction against an unshaded pane. That figure assumes the cells are sealed at the edges by side channels or by a tight recess fit. When edge sealing is lost, the reduction falls because warm air can move around the fabric instead of remaining controlled by the cellular layer.

Fit type changes performance more than fabric colour does. A pale backing facing the exterior reflects more shortwave radiation before it reaches the cell, so both the fabric choice and the way the shade sits in the reveal contribute to the final result.

Orientation sets the ceiling on what any internal shade can deliver. West glass receives low-angle sun through the late afternoon, with the rays striking the pane closer to horizontal. A shade sealing the full drop matters more here than it does on a south-facing window, where the summer sun sits higher and more of the load reaches the sill.

A Duette pulled fully down at 3pm on a west lounge is working at the point when that room would otherwise overheat. The air cells and the reflective backing need to be in place before the glass has spent the afternoon loading the room with heat.

Somfy TaHoma and Motorised Control

In many working households, a west lounge is empty for much of the afternoon. That is the case for motorising the shade. Somfy TaHoma can control Luxaflex PowerView and Somfy-motorised Duette shades on a schedule, so the fabric drops before the room heats.

The TaHoma hub pairs the shade motor with a sun sensor or with a time trigger tied to sunset, which shifts across the year. This matters on a west elevation because the heat follows a predictable arc. A setting based on solar altitude or a photocell threshold closes the shade while the reflective backing is facing the sun and the cells can still limit the early temperature rise.

Battery-motor Duette shades recharge every few months, depending on cycle count and drop length. Hardwired motors remove that maintenance, although the cable route has to be decided at fitting stage, since chasing a wall for a power feed after plastering is disruptive. On a recess fit, the motor sits in the headrail, so the reveal depth measured earlier also has to clear the motor housing, which is deeper than a manual clutch. A reveal that accepted a manual shade may be too shallow for a motorised version.

TaHoma also groups multiple shades. A run of lounge windows can drop together, which avoids a staggered closing pattern across the same west-facing wall.

Brackets and Weight

Roller and Duette brackets fix through plasterboard into a stud or into a cavity fixing rated for the headrail weight. A motorised headrail is heavier than a manual one, so a plasterboard-only fixing that held a hand-operated blind can pull out under a motor and a long drop of double-cell fabric.

A Worked Example on One Window

Take a west lounge window with a recess 1200mm wide, a 1500mm drop and a reveal depth of 90mm. The three width readings come back as 1200, 1196 and 1194mm. The order width is 1194mm, the smallest reading, so the shade clears the tightest point without binding.

The 90mm depth clears a battery motor housing comfortably and leaves space for the fabric to sit close to the glass. That closeness is part of the performance assumption behind the solar gain figure, because the sealed air layer works best when the shade sits near the pane.

Double-cell fabric goes in because the room faces the afternoon sun and loses heat through the same glass on winter evenings. A Somfy motor pairs to a TaHoma hub set to drop the shade at a fixed solar altitude in the late afternoon. Through summer, the sealed cells and pale exterior backing cut the incoming load before the room warms. Through winter, the same air chambers slow heat loss after dark.

The number on the box assumes the edges stay sealed and the fabric stays close to the glass. Whether that reveal delivers the full stated result or a smaller reduction depends on the three measurements taken before the order was placed, which is information a specification sheet cannot supply in advance.

The Roof Window Problem

Velux roof windows on a west pitch collect condensation on cold mornings when warm interior air meets cold glass. A honeycomb shade fitted tight to the pane can trap moisture against the glass if the room has no ventilation path, and the water sits in the recess. Velux specifies its own guide-rail blinds for pitched glazing partly for this reason, and side channels on a pitched window need a drainage or ventilation gap that a vertical reveal does not.

Airflow is required. A trickle vent left open or the Velux flap cracked overnight moves the dew point away from the glass surface, allowing the shade to insulate without leaving moisture held against the pane.

On a west roof pitch, the same shade deals with afternoon heat gain and morning condensation within twelve hours. The unresolved detail is the allowance around the pitched guide path: tight enough to insulate the glass, open enough to let damp air move on cold mornings.