Blackout curtains guide

What is a blackout curtain?

A blackout curtain is an opaque curtain backed with foam coating or a separate blackout lining to block light; it is most common in hotel rooms and bedrooms ^[1][7].

A dim-out curtain greatly reduces light but does not make the room pitch dark ^[3]. Note that "blackout" has no binding common threshold: test methods exist, but they do not define the level at which a fabric may be called blackout ^[4]. A major retailer also states that no blackout lining blocks 100% of light ^[5]. Besides homes, blackout curtains are used where light is unwanted, such as cinemas and theatres ^[2].

Fabric types: coating, weave, lining

The main ways to achieve blackout are foam coating (two- or three-pass) and a blackout lining sewn behind the face fabric; one product example is woven on both sides with a lamination layer ^[1][6][8].

In three-pass coating, white, then black, then white foam is applied; such fabric can serve as both face fabric and lining in one piece. Two-pass fabric is not used alone as a face fabric because the black layer can show through ^[1].

With a lining, the look comes from the face fabric and the blackout from the coated lining behind it; this combination gives the highest light absorption and insulation ^[6][7]. A blackout lining also reduces sun fading of the face fabric ^[7].

How is light blocking measured?

In the US, AATCC TM203 measures light blocking of window-covering fabrics with a spectrophotometer; in Europe, for blinds and similar solar protection products, EN 14500 defines the test methods and EN 14501 the visual comfort classes, including "darkening performance"; these standards do not explicitly name curtains ^[10][12][13].

The lab calibrates 100% with a white standard and 0% with an opaque black standard, then measures the sample ^[11]. Because the word itself guarantees no threshold ^[4], our advice: ask the maker for the test report when a product is sold as blackout.

Measuring and mounting to stop light leaks

Light can leak at the sides and the top. The curtain should overlap the window by 10–15 cm on each side, run from ceiling to floor and hang as close to the window as possible ^{[9][16][20][8]}.

We recommend mounting the curtain on the ceiling line: no light leaks over the top and the curtain covers the whole window. The layer order from glass to room is roller blind, sheer, curtain; the blackout curtain is at the front and can be combined with a blind ^[16].

For fullness, one retailer recommends a curtain width of at least 2 times the window width, or 2.5 times for a fuller look ^[20]; another multiplies the track width by 1.5 (full) or 2 (very full) ^[8]. The perde.ai studio uses 1:3 fullness by default (generous drape). Wash curtains before shortening, as fabric can shrink ^[9].

Heat and energy: how effective?

The effect depends more on mounting than on fabric. According to a university fact sheet, a loosely hung curtain cuts heat loss by only 5–10%; one closed at the top, sealed at the sides, touching the floor and separately lined cuts it by up to 25% ^[14].

The reason is air circulating in the gap between curtain and glass. To work, the curtain must fit tightly at the edges and trap air against the glass ^[14][6]. Note: this measurement comes from an older fact sheet for single glazing in a US winter climate; with modern double glazing the effect may differ ^[14]. Retailers say blackout curtains help keep rooms warmer in winter and cooler in summer but give no figures ^[7][8].

Do they reduce noise?

Thick, gathered curtains soften sound somewhat, but no measured noise-reduction values for blackout curtains appear in the sources ^[15][16].

Curtains absorb sound better when gathered in folds and hung a little away from the wall ^[15]; ceiling-mounted curtains give better sound absorption ^[16]. For serious noise, consider acoustic curtains or window insulation as well.

Fire classes and hotel use

Our advice: in public and hospitality projects, ask for the curtain’s fire classification certificate; local regulations and the project set the required class. In Europe, EN 13773 classifies curtains from class 1 (no ignition) to class 5 ^[17].

One fabric can carry several national classes: a collection certificate, for example, shows DIN 4102-B1 (Germany), M1 (France), EN 13773 class 1, BS 5867 and NFPA 701 (US) together ^[18]. In public and hospitality projects, fire regulations bring flame-retardant fabrics to the fore ^[19]. Fire tests are usually done after washing according to the care label; ask for this certificate for washable curtains ^[17].

Care and washing

Care depends on the fabric: according to one maker’s care sheet, coated blackout needs low temperatures and no dry cleaning, while one woven blackout curtain’s label allows a cold machine wash. Always read the label ^[21][8].

A maker’s care sheet for coated polyester advises mild detergent only, no more than 30 °C, no dry cleaning or tumble drying, and drying without coated faces touching ^[21]. A woven blackout curtain’s label states cold wash, low-heat drying and up to 4% shrinkage ^[8]. For routine care, curtains can be dusted or cleaned with a vacuum upholstery tool ^[5].

Sleep and light

Sleep experts recommend sleeping in a room as dark as possible; darkness triggers melatonin production in the brain, while light slows it ^[22][24].

A university study found that sleeping one night in moderate room light (100 lux) affected cardiovascular function during sleep compared with dim light (3 lux); the researchers suggest blackout shades or an eye mask if outside light cannot be controlled ^[23]. The study looked at light, not curtains; curtains are one way to reduce light. If you like waking with daylight, a dim-out curtain is an option ^[3]; a timed motorised curtain is another (see our motorised curtains guide).