With kitchen aluminum foil and styrofoam, you can create a simple and passive solar heater. The goal is not to fully cover the window but to make it smaller than the window.
You can still see the view outside and let some sunlight in the room. You may opt to completely cover the window with foil for a more effective solar heater.
Finding the Materials
It all started when I found an old sheet of styrofoam in the garage. You know, the kind that comes as packing material. I also grabbed a roll of kitchen aluminum foil, some black construction paper, and tape. You don’t need fancy materials for this. The goal is to reflect sunlight and trap heat, and these items do the job.
Assembling the Heater
I set up a little workstation in the kitchen. First, I wrapped the styrofoam with aluminum foil. I made sure the shiny side faced out because that’s the part that reflects sunlight best. I used regular tape to secure it, though glue would work too. While doing this, my kid asked if I was building a spaceship. I said, “Kind of—it’s a spaceship for heat!”
To make it more effective, I covered the front side with black construction paper. The black surface absorbs sunlight and gets warm, which is exactly what you want for a solar heater. If you don’t have black paper, you can paint the surface black, but I like quick fixes.
Setting It Up
I propped the whole thing up on a small table in front of the biggest window in my living room. The window faces south, which is important since that’s where you get the most sun in the winter. I angled the foil-covered styrofoam so it would catch and reflect sunlight onto the black paper. It felt like crafting a mini science experiment.
The sun hit the black paper within a few minutes, and I could feel the surface getting warm. I was pretty impressed. I didn’t expect such a simple design to work so quickly. I added a cardboard frame around the edges to make it look tidier (and to stop my cat from chewing on the styrofoam).
Testing It Out
That afternoon, the heater warmed up a small section of the room. It wasn’t a dramatic difference, but it definitely added a noticeable layer of warmth. I measured the temperature near the heater with a kitchen thermometer and saw it was a few degrees higher than the rest of the room.
What I love about this little project is how easy it is to adjust. On cloudy days, I just move it aside, and on sunny days, I tilt it to maximize the sun exposure. It doesn’t replace a regular heater, but it helps cut down on energy use, especially during sunny winter afternoons.
This project turned out to be a fun conversation starter. Friends who came over were curious about the shiny contraption in the corner, and I explained how it worked. Some even asked for a tutorial to try it themselves, so I decided to blog about it here.
If you’re looking for a low-cost way to harness sunlight and add a little extra warmth to your home, give this a shot. It’s quick, practical, and surprisingly satisfying to build something that works using materials you already have.
