Homemade Cardboard Solar Window Heater

--all you need is cardboard and black paint--

Your Window = Solar Heater

Overview

This simple device actually takes advantage of the setup of a traditional style window to turn it into a simple sun powered heater.

Materials:

Corrugated cardboard

Black paint

Paintbrush

Knife or scissors

South-facing window (east or west is okay but not as good)

STEP ONE-------------------------------------->
CUT a piece of cardboard to the size of the interior of the window (both top and bottom panes of the window) you wish to use. Make sure the "corrugation" is running vertically so the holes will be at the top and bottom.

Unfortunately, many stores still do not recycle their cardboard. I took the piece for this project out of the trash pile at a local rental store.

STEP TWO------------------------------------->
PAINT the cardboard black

Make sure not to get the paint in the corrugation holes, or to crush the corrugation. It will be used for air flow.

STEP THREE----------------------------------> Take the window screens out to make more space and increase light.

STEP FOUR----------------------------------->
SLIDE the cardboard into the window, black side facing outside, in the area between the storm windows and inside glass panes.

STEP FIVE------------------------------------->

RAISE the bottom of the cardboard off the window sill in order that air can flow into the bottom of the cardboard holes.

Here I use a piece of metal to prop it up. Anything that does not block the cardboard holes is fine.

STEP SIX--------------------------------------->
Crack open the window panes on the top and bottom about one inch.

This will allow air to flow in the bottom, up through the slots in the cardboard where it warms, and then back out the top and back into the room.

When the sun is out--crack open the top and bottom of the windows. Remember to close up the window at night or you will be doing the opposite--cooling! Warm air will flow in the top and cool inside the cardboard and come out the bottom window cold.

Don't want this carboard in your window all the time? Just slide it out, it only takes 5 seconds. I store mine behind the bookcase next to the window.

Another option is to paint something attractive on inside surface of the cardboard.

If you have break-in concerns regarding leaving your window cracked, you can use a safety latch like my window has (see middle right side of window picture at left). In any case, your outside storm windows will still be closed, so it shouldn't increase your risk much.

Does it work?

Here I've got air flowing in the bottom at 63 F and back out the top at a little over 100 F. Pretty hot for a piece of painted cardboard. The temperature outside is about 35 F.

OPTIONAL ADDITONAL STEPS: