These two fabrics get confused constantly, and it matters, because they are doing opposite jobs. Blockout stops light. Sunscreen lets it through but takes the sting out of it.
Get it wrong and you end up with a dark lounge you have to turn the lights on in, or a bedroom that is still bright at 6am in December.
What blockout actually does
A blockout fabric is coated so light does not pass through it. If you hold it up to a window you see nothing through it, and behind it the room goes dark.
The catch is the edges. A blind inside a shallow reveal will leak light down the sides and across the top, no matter how good the fabric is. If total darkness matters, that is a fitting question as much as a fabric one, and it is worth saying so before you order rather than after.
What sunscreen actually does
A sunscreen blind is an open weave. You can see through it, so the view and the daylight stay, but the glare and a good part of the heat are taken out of the sun before it lands on the couch.
It is the wrong fabric for a bedroom. At night, with a light on inside and dark outside, you can see in. Sunscreen is a daytime product.
So which room gets which
Bedrooms: blockout. That is the whole answer, unless the room is never slept in during daylight.
Lounges and living areas that face west or north: sunscreen during the day, and something else behind it for the evening. That second layer is usually a blockout roller, or curtains if the room wants softness anyway.
Kitchens and hallways: light filtering. You want the room bright without being able to read the fine print on the grocery list from the glare.
The two-blind setup, and why it works
On a big west-facing slider we often fit two blinds in one opening: a sunscreen for daytime and a blockout for night. It sounds excessive until you live with a single blind that is either too dark or too bright for half the day.
It is also cheaper than it sounds, because the second blind shares the same headbox width and fixing points.
Questions about this
Can I get a fabric that does both?
Not properly. A dual-purpose fabric is a compromise that does neither job well. Two blinds in one opening is the honest answer.
Does a darker blockout blind work better than a light one?
The coating does the work, not the colour. A dark face on a light backing is common, and the room behind it still goes dark.
Is sunscreen enough for a baby's room?
For daytime naps it helps with glare, but it will not make the room dark. For a nursery, blockout plus a way to manage the edges is the usual answer.
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