What blackout fabric does — and what it doesn't
A blackout fabric has an opaque backing or coating that stops light passing through the material itself. Hold it up to a summer sky and you'll see nothing come through. That's the promise, and good blackout fabric keeps it completely.
What no fabric can promise is what happens around it. A blind is a flat panel hanging in front of a window; light doesn't only travel through fabric, it leaks past the edges. So "blackout blind" really means "a blind whose fabric blocks light" — how dark the room actually gets depends just as much on how the blind is fitted as on what it's made of. Understanding that distinction is the whole trick to buying well.
The edge-gap problem
Fit a blackout blind inside the window recess and it needs a small operating clearance on each side — a few millimetres so the blind can move without scraping the plaster. On a bright morning, those slivers of gap become thin, sharp lines of daylight down each edge of the window. The fabric is doing its job perfectly; the light is simply going around it.
There are two honest fixes:
- Fit outside the recess. Mounting the blind on the wall above the window with a generous overlap on every side means light has to travel around a much bigger obstacle. This is the single most effective step for a darker room, and it costs nothing extra — it's just a fitting decision, covered in our measuring guide.
- Choose a blind with side channels or a frame. Some designs physically close the gap rather than covering it, which brings us to Perfect Fit and skylight blinds below.
Which blinds can be blackout?
More than most people expect. Blackout is a fabric property, not a product, so it appears right across the range:
| Blind type | Blackout option | Worth knowing |
|---|---|---|
| Roller blinds | Blackout fabrics in many colours and patterns | The simplest, most affordable blackout route |
| Roman blinds | Blackout lining behind the face fabric | Soft, decorative look with serious light blocking |
| Pleated blinds | Blackout pleated fabrics | Neat on smaller windows and in conservatory bedrooms |
| Vertical blinds | Blackout louvre fabrics | Useful for darkening rooms with patio doors |
| Perfect Fit blinds | Blackout fabrics within the clip-in frame | The frame hugs the glass, cutting edge gaps right down |
| Skylight blinds | Blackout with side channels | Essential kit for loft bedrooms |
A blackout roller fitted well outside the recess satisfies most bedrooms. Where you want to go further, the framed and channelled options genuinely close the gaps rather than just covering them.
Perfect Fit and skylights: the gap-closers
Perfect Fit blinds sit in a slim frame clipped into the gasket of a uPVC window, so the fabric runs tight to the glass on all four sides. There's no free-hanging edge for light to sneak past, which makes a blackout Perfect Fit one of the darkest results you can get on a standard uPVC window — with no drilling involved.
Roof windows are their own battle. In a loft bedroom the sun doesn't arrive politely at the window, it arrives overhead, and at four o'clock on a June morning. Blackout skylight blinds run in aluminium side channels fixed to the window frame, holding the fabric flat against the sloping glass and sealing the edges as they go. If a converted loft is your bedroom, this is the piece of kit that makes it work.
Who benefits most: shift workers and small children
Two groups feel the difference between "quite dark" and "properly dark" more than anyone. Shift workers — and Mansfield has plenty, with warehousing, distribution and healthcare all running around the clock — have to sleep while the sun is fully up. Daylight pressing through a thin fabric and streaming past its edges is the enemy of daytime sleep, and a well-fitted blackout blind is the cheapest, most reliable fix there is.
Babies and young children are the other. Summer evenings that stay light until ten, and mornings that brighten before five, play havoc with bedtimes. A dark nursery removes the argument that it "isn't nighttime yet". If you're planning a nursery, read our child safety guide alongside this one — darkness and cord safety should be decided together.
Layering: when one blind isn't quite enough
For the last few percent of darkness, or for rooms where you want daytime flexibility as well as nighttime black, layering works well:
- Blackout blind plus curtains. Curtains overlap the wall around the window and swallow whatever the blind's edges let past. The combination is darker than either alone, and adds insulation as a bonus.
- Two blinds on one window. A sheer or day and night blind for daytime privacy, with a blackout roller behind or in front for sleeping. Useful in bedsits, studios and bedrooms that double as offices.
- Blackout in the frame, dimout in the room. In conservatory-adjacent bedrooms and garden rooms, a blackout Perfect Fit on the glass with a soft dimout roller over the top gives both moods.
Layering is also the pragmatic answer for awkward windows where one perfect blind doesn't exist.
Get the fitting decision right — it's free to ask
By now the theme is obvious: with blackout, the fitting decision matters as much as the fabric. Recess or exact fit, overlap sizes, whether a frame or channel is worth it for your particular window — these calls decide whether you get a dark room or an expensive disappointment.
They're also exactly what our free home consultation is for. We'll look at each window, the direction it faces and who sleeps behind it, then recommend the fabric and fitting position honestly — anywhere within twenty miles of Mansfield, with measuring and fitting included and a 12-month guarantee on the work. Call 01623 325 054 or book your visit, and tell us who needs the sleep.
Frequently asked questions
Do blackout blinds block 100% of light?
The fabric itself blocks virtually all light passing through it, but a small amount can still leak around the edges of the blind, especially with a recess fit. Fitting the blind outside the recess with a good overlap, or choosing a framed option like Perfect Fit or a channelled skylight blind, gets you as close to total darkness as a blind can.
What's the best blackout blind for a Velux-style loft bedroom?
A purpose-made blackout skylight blind. It's built for the specific roof window model, runs in side channels that hold the fabric against the sloping glass, and seals the edges far better than anything improvised. Loft bedrooms suffer more from dawn light than any other room because the window faces the sky, so the channelled design earns its keep.
Can vertical blinds be blackout?
Yes — vertical louvres are available in blackout fabrics, which makes them a practical way to darken a bedroom with patio doors or a very wide window. Because the louvres overlap when closed, they block light well through the fabric, though like any blind some light can pass at the outer edges. We'll advise on the best fit at your consultation.
Will a blackout blind help me sleep during the day after night shifts?
It's one of the most effective changes a shift worker can make. Daylight is the main signal keeping your body awake, and a properly fitted blackout blind removes most of it at source. For day sleeping we'd usually suggest fitting outside the recess with a generous overlap, or a Perfect Fit blackout on uPVC windows, to cut the edge light right down.
Are blackout blinds too dark for a child's room in the daytime?
No — the blind only blocks light when it's closed. Through the day you raise or open it like any other blind and the room is as bright as ever. That control is exactly the point: dark for naps and summer bedtimes, light for playtime. Day and night blinds are another option if you want a soft filtered setting as well.