The short answer
Blackout is a fabric property, but darkness is an installation property. A blackout roller in a recess with 8mm gaps down each side will still light a room at 5am in June. The fix is in how it is mounted, not in what it is made of.
- Main leak
- Side gaps in a recess fit
- Best seal
- Side channels or a generous face fit
- Pairs with
- Shutters for daytime privacy and looks
Fabric openness, colour and light bleed
A true blackout fabric has a coated or foam backing with zero openness factor. A dimout looks similar on the roll but passes a soft glow, which is enough to keep a baby awake in June. Ask which one you are being quoted, because the price gap is small and the outcome is not.
Colour matters more than people expect. Pale blackout fabrics reflect light around the reveal edge and read brighter in the room, while a dark fabric absorbs the bleed even where the seal is imperfect. For a nursery we usually recommend the darker option for that reason alone.
Motorised tubes suit nurseries and loft rooms where the window is out of reach, and a timer that closes the blind before bath time is a small feature that gets used every single day.
Where the light gets in
Around the sides, over the top of the roller, and under the bottom bar. Fabric is almost never the problem. Any recess-mounted blind needs clearance to run, and that clearance is a light path.
This is why people conclude that blackout blinds do not work, when what has actually happened is a recess fit in a room that needed a sealed one.
Systems that genuinely darken
Side-channel systems run the fabric in a track down each edge, closing the gap. A generously oversized face fit achieves something similar by overlapping the reveal by a decent margin on all four sides.
Cassette headboxes deal with the light escaping over the roller. Together those three details are the difference between dim and dark.
- Nursery daytime naps, side channels
- Shift worker sleeping in daylight, side channels, no compromise
- Standard bedroom, face fit with overlap is usually enough
- Guest room, a good recess blackout is fine
Combining with shutters
Shutters give privacy, insulation and appearance; a blackout blind behind them gives darkness. The blind lives in the recess, the shutters face-fit over it, and each operates independently.
It is the most common bedroom specification we fit for people who have previously been disappointed by one product trying to do both jobs.
Fabric choices
Beyond blackout coating, consider whether you want thermal backing for a cold room, and whether the fabric will be seen from outside, pale backings keep the elevation consistent across a house.
Common questions
Why does my blackout blind still let light in?
Almost always side gaps from a recess fit. A face fit with overlap or a side-channel system closes them.
Do shutters give blackout?
Solid panels come close; louvred panels leave a faint line at the blade overlap. For true darkness pair shutters with a blackout blind behind.
Are side channels visible?
They are slim tracks at each edge of the window. Most people accept them readily in a nursery or a shift worker's bedroom where darkness is the priority.
Is thermal backing worth adding?
In a cold or north-facing bedroom, yes, it adds a still-air layer at the same time as the darkness.