“Blackout” is one of the most misunderstood words in window blinds. A blackout fabric is designed to stop light passing through the material itself. It does not, on its own, stop light passing around the edges of the blind. Understanding that difference is the easiest way to avoid buying the wrong product for a bedroom, nursery or media room.
Blackout fabric and a dark room are not the same thing
A conventional blind needs physical clearance around it so that it can roll, fold or lift without rubbing. Those gaps are where most “blackout” complaints come from. The fabric may be doing exactly what it was designed to do while daylight still enters at the sides, over the top or below the bottom bar.
So if the goal is “make this room as dark as practically possible”, the fabric is only one part of the specification. The way the blind sits in or over the window matters just as much.
Three levels of room darkening
It helps to think about blackout in three broad levels rather than as a single yes-or-no feature.
1. Blackout fabric
A conventional blind — typically a roller or Roman — made with a blackout fabric or lining. This gives good room darkening and suits most bedrooms, but there will usually be some light around the edges because of the normal operating clearances.
Roman blinds are worth singling out. An opaque or blackout-lined Roman blind can give strong dim-out, but light can still pass around its edges, and stitching lines can let through small points of light. The construction of a Roman blind does not create a true blackout system on its own.
2. Enhanced room darkening
Closer-fitting arrangements can reduce the extra light further. Depending on the window, this might mean a blind fitted outside the recess with generous overlap, a cellular blind, a guided system, or a blind fitted directly to the window frame such as Perfect Fit blinds or FITtoFRAME blinds, depending on the frame.
3. Specialist blackout systems
Purpose-designed systems manage edge light with features such as a cassette at the top, side channels, or integration with the window frame. These are the closest to a very dark room that a blind can get, but performance still depends on the exact system and the window, so we would not describe any system as “total blackout” without evidence for that specific product and installation.
Why complaints happen
Many people buy blackout fabric expecting zero light. The material blocks light through the fabric, but light still enters around the edges, brackets or recess. Changing to a different or more expensive blackout fabric will not help, because the problem is geometry rather than cloth.
Common places for light gaps include:
- the sides of a recess-fitted roller blind;
- above the top of the blind;
- around window handles;
- below the bottom bar;
- where the window or reveal is not perfectly square;
- between separate blinds on a wide opening.
Inside or outside the recess?
A blind fitted inside the recess looks neat, but the fitting clearance can leave visible edge gaps. A blind fitted outside the recess can overlap the opening, which often improves room darkening. Face fitting is not automatically the answer, though: radiators, furniture, architraves and the look of the window all need considering. Our guide to inside vs outside recess fitting covers this in more detail.
What about shutters and curtains?
Conventional louvred shutters are excellent for privacy and adjustable light, but they are not an engineered blackout system. See Are Shutters Blackout? for the options if you love shutters but need a darker room.
Blackout curtains follow the same principle as blinds: the lining stops light through the fabric, while light can still come around the edges, over the track and through the centre overlap. Layering a blind with curtains is often one of the most effective ways to darken a bedroom. Our comparison of blackout curtains vs blackout blinds explains the trade-offs.
A buyer's checklist
Before choosing a blackout product, it helps to answer these questions:
- How dark? Is ordinary bedroom darkness enough, or do you need near-total darkness?
- Inside or outside the recess? Is there room to fit over the opening, and would that suit the window?
- Side gaps: would a thin line of light at the edges bother you?
- Who is the room for? A nursery, shift work or light sensitivity may justify a higher level of specification.
- Layering: would curtains over a blind be practical and welcome?
- Specialist system: is the need strong enough to justify a cassette, channel or frame-fitted system?
Your answers point towards one of the three levels above. A conventional blackout roller suits many bedrooms perfectly well; a shift worker or a light-sensitive child may be better served by a specialist system or a layered scheme.
The honest way to specify blackout
Instead of asking only “is this fabric blackout?”, ask “how will this complete blind control light at this window?”. That question leads to a much more useful answer, and it is the one we work through on a home survey.
Frequently asked questions
Will a blackout blind make my room completely dark?
Not necessarily. The fabric stops light passing through it, but light can still enter around the edges. How dark the room becomes depends on the fitting position and the type of system.
Would a darker or thicker fabric stop the light at the edges?
No. Edge light comes from the gaps around the blind, not through the fabric. Reducing it means changing how the blind is fitted or choosing a system designed to close those gaps.
Are blackout Roman blinds as dark as blackout rollers?
A blackout-lined Roman blind can give strong room darkening, but light can pass around its edges and through stitching points. For the darkest result, a Roman is often best paired with another layer or a specialist blind.
What is the darkest option for a nursery?
It depends on the window. A specialist blackout system with side channels or frame integration, or a blackout blind layered with curtains, will usually get closer to a very dark room than a standard blind alone.