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How to Build a Heat Box for $6, Heat your Home Free

Saturday, May 3, 2014 10:46
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 The EPA, and Mother Earth, have expressed interest in “Passive Solar Heat Box” units for home and commercial building heating. We decided to build one, 4.5′ by 6.5′ to check it out. Using old 2 x 4′s, some polycarbonate panels we had in storage, we built a box, spray painted screen wire black, tacked aluminum foil on the back wall of the box. When the sunlight came through the polycarbonate, it hit the “black” screen wire, and some of the light hit the aluminum foil and that reflected back creating more heat. We cut a hole in the bottom of the back wall and a hole in the top, and sealed it all tight with silicone. To our amazement, after only 10 minutes in the sun, the box was throwing out a breeze of hot air (130 to 140 degrees F) while the temperature outside was 78 degrees. We tested it several times and even when few clouds passed by, managed a 40 to 60 degree spread. We have been told that if you add bottles of anti-freeze, or rocks, in the unit (would take a larger, deeper unit) that the heat will keep on for about 6 hours after the sun goes down. I plan to put a little solar powered fan on mine to get even more volume of air. I have a basement that is hard to keep warm. It is always 30 degrees cooler than any other room in the house, and I’m going to “Passive solar” heat my “man cave”. In this case, the EPA, and MOTHER EARTH NEWS had a great idea. We know there are commercial units available out there, but it was fun building something, especially something that worked. If your house or commercial buildings have energy efficiency units they sell for more, have higher occupancy, and higher rents. The also appraise for more. Put one of these on your Green House and you can heat it even more, and grow vegetables all winter. See: Give us a call:, or 800-379-8048. Directions: 1. Build wood frame 2. Put aluminum foil on inside of back 3. Install wire screen 2″ above the foil 4, Cover the entire frame with polycarbonate to allow the sun to come in hit the foil and reflect and concentrate the heat on the “black wire”. 5. Cut a hole at the top of the back wall and another at the bottom of the front polycarbonate wall. 6. Cut a vent hole to match each in your wall, be sure you use an AC vent that can be opened or closed seasonally. 7. If you want to control the speed of the air, install a fan to pull or push the air through.


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Total 8 comments
  • True News

    This idea is like the thermal solar panels of the 1970′s. It’ll definitely work and there are some designs you can find on the internet that will improve efficiency of collection.

    • Thane36425

      One of my high school teachers in the 80s had something like this. His place was just a little cabin and it did alright heating it, though he did have other heat sources for the deep winter. So they have been around for some time.


    I made my box from 4′x8′x6″ lumber. About 8 inches from the top and bottom is dam or reservoir if you will. The bottom reservoir is for cool air to enter from the floor level of the room I’m heating through a 6″ insulated duct. The top reservoir is where the hot air mixes and is blown into the room at the ceiling height, again through 6″ insulated duct. I covered the whole thing with a 4′x8′x 1/2″ piece of plate glass that used to be a dinning room table. Between the reservoirs there are (8) 4 inch pieces of water heater vent pipe. The entire interior including the piping is painted a non-glossy black. At the bottom I have an electric fan that is connected to a thermostat. When the thermostat inside the boxes exceeds 100F the fan comes on. On a bright sunny day with the outside temperature in the twenties the unit consistently puts out between 100F and 140F. The exhaust vent at the top is louvered like a dryer vent and prevents heat running backwards through the device at night. It’s free heat. We have used it for so long that we now take it for granted. I plug in when the nights start to get cool, around October and don’t think anything else about it all winter. It is self regulating so no worries.

    • Anonymous

      Please, write your own prescription and post it here. We need it. Pics. instructions, etc.


      – you’re an absolute idiotic moron!

  • Anonymous

    Brilliant! Deserves wide diissemination. I would appreciate full disclosure with material needs and pictographic instructions as others would I am sure.
    Appreciate your efforts and ask that you build on your knowledge and experience. Let us know how it goes.
    Thank you so much. This is the only future.

  • Anonymous

    Why would you bother to heat your home if it was 78º out? Makes no sense.

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