DIY Blackout Blind For Free

The room I'm currently sleeping in has blinds which let in a lot of light. And since there are street lights outside my house, the room is not very dark at night.

Thin yellow blinds

Q: How to create a blackout blind for free*?

*this is for free if you have the bits already in your house

Firstly, measure out the inside of the window.

My example above measures about 86.5cm on the sill, 86cm at the top (not a perfect rectangle ... they rarely are), and 127cm high.

We're not doing precision engineering here (doesn't need it), so I'm going to say:
  • 88cm width
  • 128cm height 
We're going to make a blackout blind using 4 pieces of cardboard and we need them to overlap each other, so I'm going to half the above numbers and add between 10 and 20%

44cm -> 50cm
64cm -> 75cm

So we're looking for cardboard we can cut out into roughly 50cm x 75cm pieces.

I have a box which when flattened is 82cm wide, and just over 2 metres long. Taking into account the folds, I cut it into these pieces:

2 x 50cm x 82cm
2 x 58cm x 82cm

4 bits of cardboard

Then we start forming it into shape by positioning it within the inner window and taping together:

Building into the corners with first 2 cardboard pieces

The completed blackout blind:

4 bits of cardboard taped together

Of course, the above looks a bit rubbish, so we can improve this by covering it in kitchen foil. And voila:

Finished Version 2 Free Blackout Blind (inside window frame)

The above is blackout blind version 2. I also have a version 1 (below) that fits outside the window frame (as opposed to inside the frame) and uses white Velcro to attach to the wall. Combining both version 1 and version 2 virtually eliminates light coming from outside, and all for free (because I had the stuff in my house already.)

Original Version 1 Blackout Blind (outside window frame)

This was constructed from polystyrene foamy stuff (not totally sure the right name for it.