The gap between "room darkening" and "blackout" is bigger than most people think. A room-darkening blind might block 80% of light. A proper blackout blind blocks 99%+. That remaining 20% is enough to suppress your melatonin production and mess with your sleep quality, which is why you're still waking up tired even though you bought blinds.
Why bedroom light matters more than you think
Your brain treats any light during sleep as a signal to produce less melatonin. A study we covered in our sleep mask article found that even dim light, roughly the level of a TV standby LED across the room, increased overnight heart rate and impaired glucose metabolism the next day.
Blinds are the first line of defence because they deal with the biggest light source: the window. Streetlights, car headlights, early morning sun, the neighbour's security light that fires up every time a fox walks past. If your window isn't properly blacked out, everything else you do for sleep hygiene is working harder than it needs to.
Types of light blocking blinds
Blackout roller blinds
The most common option. A single piece of blackout fabric on a roller mechanism. They work well when fitted inside the window recess with minimal gaps. The problem is light leakage around the edges. Even a 5mm gap at the sides lets in a strip of light that your eyes will find at 5am in summer.
Fix: buy slightly wider than your recess, or use side channels (U-shaped tracks that the blind runs in). Some brands sell these as "cassette blinds" with a headbox that seals the top edge too.
Price: £15-40 for a standard window. More for custom sizes.
Thermal blackout blinds
Same as blackout rollers but with a thermal coating on the back. They block light and insulate the window, which keeps the room cooler in summer and warmer in winter. If you're choosing between standard blackout and thermal blackout, the thermal version costs a few pounds more and does more.
Blackout window film
Self-adhesive film that sticks directly to the glass. Blocks 100% of light with zero edge gaps. The downside: you can't see out of the window during the day, and removal can leave adhesive residue on the glass. Good for rooms where you never need daylight (a dedicated dark room for a shift worker, for example) but impractical for a normal bedroom.
Our blackout blinds for shift workers article covers this option in more detail for people who sleep during the day.
Portable blackout blinds
Suction-cup mounted fabric panels that stick to the window glass. No drilling and no permanent installation. Travel versions fold flat and go in a suitcase. Useful for rented accommodation where you can't install proper blinds, or for a child's room where you want blackout for nap time and daylight the rest of the day.
Blackout curtains
Not blinds, but worth mentioning since many people use them instead. Curtains hang in front of the window and overlap the wall on both sides, which naturally covers more of the light gap than blinds do. The trade-off is that curtains take up more space and can look heavy in a small room. Our best blackout curtains UK guide compares specific products.
The edge-gap problem
This is the thing most people get wrong. They buy a blackout blind, fit it, and still get light around the edges. The blind fabric blocks light perfectly. The installation doesn't.
Solutions ranked by effectiveness:
- Cassette blinds with side channels - seals top and sides
- Blinds fitted outside the recess, overlapping the wall by 5-10cm each side
- Blinds fitted inside the recess with foam tape along the edges
- Adding a blackout curtain over the top of the blind (belt and braces approach)
For bedrooms where you need complete darkness, option 1 or 4 is the way to go. For "good enough" darkness, option 2 covers most people.
What to look for when buying
Fabric weight matters. Heavier fabric blocks more light. If you can hold the fabric up to a window in a shop and see any light through it, it's not blackout. Real blackout fabric is opaque.
Check for a white or silver backing. This reflects heat and light rather than absorbing it, which keeps the room cooler. Black-backed blinds absorb heat and can make a south-facing bedroom uncomfortably warm in summer.
Measure your window properly. Measure twice. A blind that's 2cm too narrow defeats the entire purpose.
Blinds vs sleep mask
A sleep mask is cheaper and faster. You put it on and the light is gone. But it only blocks light for you, not the room. If you share a bed, your partner still gets the light. Do sleep masks actually help? Our article covers the science.
Blinds fix the room. Everyone in it benefits. They also add insulation and privacy. The ideal setup is blackout blinds for the window and a sleep mask for situations where the blinds aren't enough (summer mornings, hotel rooms, napping on the sofa).
Waking up in a blacked-out room
One genuine problem with complete darkness: waking up is harder. Your body uses light to regulate cortisol, the hormone that makes you feel alert. Block all light and your body doesn't get the dawn signal.
A sunrise alarm clock fixes this. It simulates dawn by gradually increasing light 20-30 minutes before your alarm. Works well alongside blackout blinds because you get total darkness for sleeping and a controlled light increase for waking.
FAQ
Are blackout blinds worth it for bedrooms? If light is getting into your bedroom and affecting your sleep, yes. They're one of the cheapest home improvements with a direct impact on sleep quality. The return on a £25 blind is better than most sleep supplements.
What's the difference between room darkening and blackout? Room darkening blocks most light, typically 80-95%. Blackout blocks 99%+. For sleep, the difference matters because your eyes are extremely sensitive to light when your pupils are dilated in the dark.
Do blackout blinds make a room too hot? Black-backed blinds can trap heat. Silver or white-backed blinds reflect it. If your bedroom faces south or west, choose a reflective backing. Thermal blackout blinds are specifically designed to insulate without overheating.
Can I fit blackout blinds in a rented flat? Portable suction-cup blinds require no drilling and leave no marks. Tension rod curtains are another option. Or use a sleep mask as a stop-gap.
