"Barn Door" Style Insulating Blackout Shade for Apartements

...A high performance room-darkening blackout shade, which uses a leaf spring to install temporarily into your windows, and is easy to slide open and closed.

I recently moved into a new apartment complex, and while I like sleeping in dark rooms, the landlord-company really likes their security lighting... and, of course, don't like people to do minor carpentry on their properties. A bit of thought generated the following list of project goals:

• Block lots of light.
• Install in a manner which will not damage the window or leave any holes which would have to be patched.
• Break down into components which I could fit in my car - I had to fabricate the project off-site.
• Be easy to open and close. I like sunlight during the day.
• Open in a fashion which would not prohibit me from putting a desk in front of the window - so it couldn't just be hinged on the side.

The result was this project. It was a bit of a rush job on both the design and fabrication sides, so I made some mistakes, which I'll note when they occur - but it still works well. Please see the photo's markups for construction details, or below for overall design principles...

Light-Blocking Design: In the closed position, all straight-line paths that light could follow into the room are eliminated. This is accomplished by a variety of tongue-and-groove geometries on both the edges of the sliding panels and the frame which mounts into the window. All light-blocking surfaces were then painted with a high-quality flat black paint. Where this plan was successfully followed, there is little light leakage...

Temporary Mounting: The frame mounts itself forcing rubber pads against the top and bottom of the window opening; the bottom bar of the frame is designed as a leaf spring (use your usual beam-bending calculations, or intuition) so that the frame can expand and contract while still applying a reasonable "clamping" force. This works well.

Panel Construction: My panels are foam with wood edges.

The foam is 3/4" foil-faced polyisocyanurate, which is cheap, lightweight, easy to cut, lightproof, (sufficiently) water-resistant, and (bonus!) thermally insulative to keep you warm and your heating costs down. The inside of the panel could be painted or wallpapered if you'd prefer not to have big matte silver rectangles on your walls.

The wood protects the foam panel and provides something for you to make those light-blocking flanges out of... but solid wood sticks will warp when you remove a large sector (oops). If I were doing this project over again, I'd make the edges either by gluing up small strips or from an engineered wood product, like plywood, which basically doesn't warp or change size.