Cellular shades, an air pocket at the glass.

What the honeycomb is actually doing

Still air is a poor conductor of heat. Folding the fabric into cells traps a layer of it against the window, so the shade behaves less like a curtain and more like a thin insulating panel — working in both directions, against summer heat coming in and against a cold snap pulling warmth out.

How much it changes a given room depends on the window, the exposure and the fit, so we would rather point you at the published research on window coverings than put a number of our own on it. The coastal guide below carries the sourced version.

Light-filtering, room-darkening and blackout cells

Cellular fabric is opaque in a way a solar screen never is: you do not see out through it, and the light that does come through is diffused into an even glow rather than a bright patch. That makes it a natural bedroom and nursery product.

Room-darkening and blackout cellular go further, sometimes with a foil-backed cell. As with any shade, the fabric is only half of a dark room — light still travels the edges of the opening unless the shade is channelled or generously overlapped, which we work out at the measure.

Top-down/bottom-up, and cordless operation

Top-down/bottom-up is the feature that has no equivalent on a roller. The shade is anchored at both rails, so you can drop it from the top and leave the bottom open, or raise it from the bottom and leave the top open — daylight over the head height of the room while the lower half of the glass stays private.

That is genuinely useful on a street-facing bathroom, a front bedroom or a kitchen window over a side yard. We recommend a cordless lift for cellular shades, and they motorize cleanly on a rechargeable motor.

• Bottom rail up: privacy at eye level, daylight above
• Top rail down: view and airflow at the sill, screening above
• Both rails motorized: the same two positions on a scene or a schedule

Cellular or roller — how we decide

The two products answer different questions. Choose a roller when the view is the point and glare or heat is the problem, because a solar screen keeps you looking out. Choose cellular when the room needs insulation, soft even light, or privacy that does not depend on the time of day.

Plenty of homes use both — cellular in bedrooms and west-facing rooms, solar-screen rollers across the living space and the water side.

Measuring, fit and living with them

Fit matters more on cellular than on most shades, because a wide side gap defeats the insulating layer you paid for. We measure for the tightest sensible inside mount, or a deliberate outside mount with real overlap when the opening will not take one.

Day to day they ask very little: dust the faces, and vacuum the cells gently with a brush head rather than washing them. In consistently damp rooms — a windowed shower, an unconditioned lanai-adjacent space — we will usually steer you to a shutter or blind instead, and say so at the consultation.