How To Build A Passive Solar Heater

A passive solar heater is a simple thing you can make to help heat your home. It obviously will not work at night, but it can reduce heating costs during the day. This solar heater is very simple and can be made with items already in your house.  This heater works in a similar way to a solar oven, but is simpler and doesn’t get as hot.  All you have to do is place the heater in a window that gets sunlight. The black paint warms the trapped air in the bin till it leaves through the top hole, drawing in colder air through the bottom holes in a chimney effect.  This type of heater is perfect for a greenhouse or to supplement heat in a colder room in your house.   They can add a significant amount of heat if you use multiple heaters.

You will need:

  1. Clear rubbermaid bin (Different sizes will produce different amounts of heat).
  2. Black paint (flat finish).
  3. Paint brush (or spray paint in item 2).
  4. Clear plastic wrap (clearer the better and thicker is better too).
  5. Cutting tool for plastic (doorknob drill bit 2″ in diameter works best).

The basic construction is this:

  1. Cut 2 holes in one of the short sides. The is now the top, the heater stands on the other end.
  2. Cut 1 hole in the long side near the bottom. Do this on both sides.
  3. Paint the inside of the bin black. Do not paint the side or top walls, only the back and the bottom. (if your bin isn’t clear then painting the walls is a good idea too)
  4. Cover the opening where the lid goes with the clear plastic wrap.  Making sure that there is an airtight seal around the plastic and that there are minimal wrinkles once applied.  Sometimes a hair dryer will make the wrinkles disappear.

Below is a diagram of the finished heater.  As you can see it is very easy to make.  It is a good project to make with your kids and as I mentioned before, all they do is save you money in the long run.

Note: more/larger holes means more airflow at a lower temperature, fewer/smaller holes means less airflow at a hotter temperature. There will be some trial and error to find the right balance for your desired comfort zone. You can also experiment with different materials, and different sizes.  I have thought about building one that magnifies the sunlight entering the heater with some lenses and mirrors, but have not at this time built one that way.  One good addition would be insulation on the sides and back to assist in heating the air inside, well to prevent loosing the heat inside.

This one is designed to be installed inside.  There are many variations on this design and some of them are designed to be outside and funnel heat inside the home.  Below is an example of an outdoor solar heater.  This type is more complicated to build, however you wont be blocking your windows with a large black box.  The downside is you will have to remove it every night to prevent heat loss through an opened window.  So as you can see both designs have advantages and disadvantages.  Choose the design that best suits your needs and enjoy some savings in your energy bill.

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8 thoughts on “How To Build A Passive Solar Heater

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  3. We get sunlight through east, south and west windows during the day. Would this solar heater produce more heat than the sun shining straight through my windows? These seem easy and simple to build and use. I just wondered if they would add heat or block the sun’s heat I’d be getting anyway.

    • That is a great question Mary. The short answer is yes. These heaters are designed to use the same amount of the sun’s energy that comes through the window naturally. The advantage they have is transferring the heat into the air more efficiently because they are heating a smaller volume of air at a time. If you have a lot of black in the room you are considering then the heat gained with a heater will be less. The heat gained in a white room will be very noticeable. Also, multiple heaters may be required.

  4. Thank you for the information. My mom lives with me and, although we live in E. Tenn., I am concerned about a back-up heat source if our power goes out. This seems quick and easy. I realize I will probably still need some type of back-up heat, but this would help in the daytime. She likes it toasty.

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  7. It’s a heat radiant heat collector. It’s also a convective heat sink. The question is whether you collect more energy than you shed off through convection. It’s been too long since I’ve cracked open my thermo books. But the break-even calcs are simple iirc.

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