Looking at the different types of blinds available, all of them offer a blackout option to a different degree.

1. The Advantages and Disadvantages of
Each Blind Type

2. Looking at the different types of blinds available,
all of them offer a blackout option to a
different degree. Some only meet that
description in the sense that it blocks out a
percentage of the light coming into the room.
Let's look at the different types of blinds and
judge the performance of each.

3. Vertical Blinds are the least likely of any blind to
bring a substantial reduction of light into the
room. The reason being is the way they are
designed. Let's look at a window say 100cm *
100cm with a slat size of 89mm. There will
typically be 14 slats of fabric on a vertical
blind that size, each slat overlaps the slat next
to it allowing a certain amount of light to come
through. Taking into account there are 14
slats, light will be coming through the blinds at
each overlap. Hardly the best option even if
the fabric itself is blackout.

4. Venetian Blinds and Wooden Venetian Blinds
encounter a similar problem; there are
essentially a number of slats overlapping the
one next to it, allowing for light to come
through. Although the normal venetians close
tighter to the slat next to it than even the
vertical blinds, it's not tight enough to stop
light coming through. Wooden Venetian are
probably the worst slat type blind to block out
light due to the thickness of the wood causing
the gap to the slat next to it not intended to be
tight closing.

5. Roman Blinds are in my opinion the second best
option for a blackout blind. They are the most
stylish giving you the option of style as well as
function. The lining used on the back of the
main fabric provides the blackout function,
therefore not interfering with the design. They
also fit the tightest into the recess where the
blind is fitted, preventing hardly any light
coming in at the sides.

6. Roller Blind ranges typically offer the largest
choice of fabrics option but again due to their
design allow too much light into the room. The
size of the brackets used to hold the blind up
results in the width of the fabric being around
33mm narrower than the width of the blind
including its brackets, therefore allowing light
into through that 33mm of the window recess.
Finally, the best option is a Cassette Roller
Blind. A roller blind is fitted inside a typically
white powder coated aluminum frame. The
frame fits snugly in the window recess and the
fabric providing the blocking out of any light.
As the frame prevent any light coming through
the sides, top or bottom of the blind, it gives
you the complete solution for a blackout blind.

7. blackout blind:
http://www.duette.co.uk/blackout-blinds/