How to choose a blackout curtain for a bedroom?

A blackout curtain is a curtain made of lined or tightly woven fabric that completely or almost completely blocks outside light. It differs from the classic curtain by its weft density and, often, by an integrated thermal lining. For a bedroom, it fulfills three essential roles: promoting sleep by creating deep darkness, reducing noise pollution from outside and limiting heat loss through windows. Choosing the right blackout curtain involves taking into account the fabric, dimensions, fixing system and color — each criterion directly influences the effectiveness of the result.

Why does darkness in a bedroom really improve sleep?

Darkness is not just a comfort: it is a biological signal. According to the National Institute of Sleep and Vigilance (INSV), the light perceived by the retina inhibits the secretion of melatonin, the hormone that triggers sleep. Even dim ambient light, such as the glare of a street lamp, can disrupt sleep cycles.

For children, shift workers or anyone sensitive to morning light, a blackout curtain is not a luxury but a functional answer. According to Inserm, the quality of sleep is directly linked to circadian regulation – and the light environment of the bedroom is part of it.

What is the difference between a blackout curtain, a thermal curtain and a lined curtain?

These three terms are often confused, but they designate distinct properties. A blackout curtain blocks light with a high weave density or a dark backing. A thermal curtain reduces heat exchange between the window and the room thanks to an insulating lining – generally polyester or interlining. A lined curtain combines a decorative face with a lining fabric sewn on the reverse, with no guaranteed thermal or blackout properties.

According to ADEME, windows and glass walls are responsible for a significant part of heat loss in a home. A blackout thermal curtain — combining both properties — therefore constitutes a relevant response for a room facing north or poorly insulated.

• Blackout curtain — Blocks the light. Main property: opacity. Ideal for rooms facing east or nighttime urban lighting.
• Thermal curtain — Reduces heat loss. Main property: insulation. Relevant for cold or poorly glazed rooms.
• Thermal blackout curtain — Combine the two. Main property: opacity + insulation. The most complete solution for a bedroom.

How to correctly measure your windows for a blackout curtain?

Measurement is the step most often botched — and the most determining for occulting effectiveness. A curtain that is too narrow lets light pass through to the sides, canceling the desired effect. The width of the finished fabric should be at least twice the width of the bead to ensure sufficient pleating and full coverage.

For the height, the curtain should ideally fall to the floor or 1 to 2 cm from the floor. Installation at height, by fixing the rod 15-20 cm above the window frame, visually enlarges the room and reduces light leaks at the top of the panel.

1. Measure the width of the rod or track from end to end.
2. Multiply this measurement by 2 (for a standard pleat) or by 2.5 (for a more generous pleat).
3. Measure the height from the top of the rod to the floor, then subtract 1cm.
4. Add 15 to 20 cm if you want to attach the rod above the frame for a more covering effect.
5. Check that the two panels overlap at least 5 cm in the center to avoid light leakage.

Which fabrics to choose for a bedroom blackout curtain?

Velvet, dense jacquard and flock-backed fabrics are the most effective materials for blackout. Velvet also absorbs some sound, making it a relevant choice for street-facing rooms. Jacquard — structured relief weave — offers natural opacity without lining, with an elegant drape.

Fabrics with integrated thermal lining (often coated polyester or interlining) combine concealment and insulation. They are heavier and require a sturdy rod. For children's rooms, choose OEKO-TEX Standard 100 certified fabrics, which guarantee the absence of harmful substances in the finished fabric.

• Velvet — High opacity, acoustic absorption, generous drape. Suitable for adult bedrooms and warm environments.
• Dense jacquard — Woven patterns, natural opacity, no lining required. Brings character to the room.
• Fabric with flocked or coated backing — Maximum occultation, often thermal. Ideal for rooms exposed to lots of light.
• Thick linen — Partial opacity (semi-blackout), breathable, natural. To be reserved for rooms with little exposure or to be combined with a night curtain.

What color blackout curtain to choose for a bedroom?

Color does not affect the level of blackout — it is the structure of the fabric or the lining that determines the opacity. A white curtain can be as blackout as an anthracite curtain, provided it has the same composition. On the other hand, dark shades absorb solar heat better in summer, which can warm the room slightly.

For a bedroom, muted and soothing palettes are preferred: sandstone, slate, verdigris, soft ocher or warm ivory. These colors match natural materials (wood, linen, washed cotton) and contribute to an atmosphere conducive to rest. Bright or high-contrast colors can be visually stimulating — avoid in a space dedicated to sleep.

How to properly install a blackout curtain to avoid light leaks?

The effectiveness of a blackout curtain depends as much on the installation as on the fabric. Three areas are systematically neglected: the sides (space between the curtain and the wall), the top (space between the rod and the ceiling) and the center (space between the two panels).

• Attach the rod to the ceiling or very close to it — Reduces light leak at the top of the panel.
• Extend beyond the window by 15 to 20 cm on each side — Avoids side halos at sunrise.
• Allow a central overlap of 5 to 8 cm — Essential for east-facing windows.
• Use a wall rail with return — The rail with wall return presses the fabric against the wall and eliminates leaks on the sides.
• Choosing Rings Without Excessive Spacing — A spacing of 8 to 10 cm between rings guarantees regular pleating with no gaps between the folds.

What are the common mistakes to avoid when choosing a blackout curtain?

The most frequent errors do not come from the choice of fabric but from the dimensions and installation. A poorly installed technically blackout curtain will be less effective than a well-sized ordinary curtain.

• Take the width of the window as a basis for measurement — You have to measure the rod, not the frame. A common mistake that produces a curtain that is too narrow.
• Forget the overlap in the center — Two panels that barely touch each other allow a stream of light to pass through, which is very visible at night.
• Choosing a fabric that is too light while believing that the photo will be obscured — Always check the composition and the word “blackout” on the product sheet.
• Neglecting the height fixing — A rod placed flush with the window frame systematically creates a halo of light at the top.
• Ignore fabric weight — A thermal blackout curtain is heavy. A rod that is too thin or poorly secured will sag and create side gaps.
• Confusing “lined” and “blackout” — A lined curtain can be very transparent if the lining is thin. Only the explicit mention “blackout” or a high weight guarantees opacity.

Madura expertise

Sources

• National Institute of Sleep and Vigilance (INSV) — Light and sleep, impact on melatonin — institut-sommeil-vigilance.org
• Inserm — Circadian rhythms and sleep quality — inserm.fr
• ADEME — Thermal insulation of housing, role of glass walls — ademe.fr
• OEKO-TEX — Standard 100: absence of harmful substances in textiles — oeko-tex.com
• GINETEX — Laundry care symbols (ISO 3758) — ginetex.org

Frequently asked questions

Last updated: June 2026

By Laurine Didier

In charge of content and decoration advice at Madura.