Pleated fabric forming hexagonal air cells in profile — the best-insulating interior blind made, and a genuinely useful buffer against a valley that runs hot in summer and properly wet in winter.
Trapped air is insulation. That's the whole idea behind a cellular blind, and it's a genuinely useful one in a valley where a north or west-facing room can run hot through a long summer afternoon and then feel the chill of a proper wet Cape winter a few months later. Single cells suit milder rooms, double cells do the serious thermal work — cooler summer rooms, warmer winter ones, and a bit quieter too, since the cells absorb sound as well as heat.
Energy-conscious renovations, bedrooms and nurseries that need dark-quiet-warm all at once, and any room where the family has noticed “that side of the house is always the hot one in summer and the cold one in winter” — a fair description of quite a few Durbanville homes built to face the afternoon sun and the view together.
Free in-home measure, a written per-window quote, and a straight answer if cellular isn’t the right fit.