What actually blocks light.
Fabric does part of the work. A triple-weave blackout fabric blocks 95 to 98 percent of light passing through the body of the curtain. Room-darkening (single-pass) blocks 90 to 95 percent. Standard lined curtains block 60 to 80 percent. The fabric label tells you which.
Sizing does the rest. A blackout curtain that is too narrow lets light leak in at the sides; a curtain that does not reach the floor lets light leak at the bottom. The rule: curtain width should be 1.5 to 2 times the window width (so the curtain stacks open without thinning over the glass), and the curtain should overlap the window frame by at least 6 inches on each side and reach the floor or windowsill.
Header style matters too. Grommet and tab tops always leak light at the rod because the curtain pulls away from the wall. Rod-pocket or pinch-pleat headers with a ceiling-mounted track and a return arm to the wall close that gap.
Common questions.
- What is the best blackout curtain fabric?
- Triple-weave or three-pass blackout fabric blocks 95 to 98 percent of light by itself. The denser the weave and the more passes (layers within the fabric), the better the blocking. For hotel-room blackout standard, specify triple-pass blackout.
- Do blackout curtains need a separate liner?
- Triple-weave blackout fabric does not need a separate liner. Decorative curtains with a separate blackout liner deliver similar performance and let you choose any face fabric. Both approaches work; choice depends on aesthetic preference.
- How wide should blackout curtains be?
- 1.5 to 2 times the window width with at least 6 inches of overlap on each side of the window frame. Narrower curtains leak light at the sides regardless of fabric density.
Project in motion
Specifying blackout window treatments?
We source blackout curtains and drapery on the full Crateworks soft furnishing program. Send window dimensions and the room use.