R-Value (Insulation)

R-value measures resistance to heat flow; a higher number means better insulation. Cellular shades quote it because their trapped-air cells genuinely slow heat loss and gain, and double-cell and side-tracked versions read higher than single-cell. Two honest caveats keep it in perspective: a shade’s R-value applies only to the glass it covers, so whole-room comfort depends on the window, the seal, and how much of the day the shade is down; and manufacturer figures come from favorable test conditions. Treat R-value as a real, comparable spec within the cellular category — and as one input to comfort, not a guarantee of a warm room.