It may be the most wonderful time of the year, but it sure is cold. In some places, it’s so cold that an extended power outage could be deadly. Hopefully, you’ve prepared your home for winter and have several ways to heat your home without power, but there is one way to heat your home that doesn’t require any fuel or firewood: a solar furnace.
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A solar furnace could keep a single room nice and warm on a sunny day. This would be great if the power went out as you wouldn’t have to use any of your fuel. Just be sure to put it on the south side of your house.
In this video, TheGulley shows off a solar furnace that he built for less than $50.
Here’s what you need:
- Two window panes.
- 3×5 foot sheet of black pastic.
- Two pieces of lumber around 2×10 inches and 3 feet long.
- Two pieces of lumber around 2×10 inches and 5 feet long.
- Another piece of lumber as long as the width of your window.
- ABS or PVC pipes and elbows.
- A standard dryer hose.
- Black spray paint.
Here’s how to build it:
- Build the frame using all the 3 and 5-foot pieces of lumber.
- Attach the sheet of black plastic to one side of the frame.
- Cut a hole in one end of the frame large enough for the pipe.
- Connect the pipes from the end of the frame into a nearby window.
- Attach the dryer hose to the other side of the hole and have it wind back and forth so it all fits inside the frame.
- Spray paint the dryer hose black.
- Attach the window panes.
- Cut holes in the fifth piece of lumber. One hole is for the exhaust pipe coming from the heater. The other hole is for the intake to draw air out of the house.
- Shut window against that piece of lumber and put the exhaust and intake pipes in place.
Be sure to watch the video below to see exactly how he did it.
Like this post? Check out these 17 ways to stay warm when the power goes out.
The most this is likely to generate is a few degrees warmer than the outside air. To many factors that will result in heat loss during the transfer. Its likely the window is providing more solar heat than this box is. Now if you placed this on the inside of your window you might get better results but even then not much.
The box may be mounted on the south side of the house, but angling it toward the sun, perhaps at a 60-degree angle, with the base out from the wall would capture more solar energy. He didn’t say how he fastened the windows to the box, or if he caulked the joints – I sure would have done all I could to seal out cold air. He’s sucking air out of the house that’s warmer than the ambient outdoor air in winter, so it makes sense to seal the box to prevent invasion of cold outdoor air. I’d also be looking for a south-facing house window without bushes or other obstacles underneath, to make sure the hot-air pipe had as short a run as possible.
Using a sheet of black plastic for the backing??? Maybe for the low-cost factor – that size is about what a large drum-liner or lawn & leaf bag would make, cut and opened up. That’s not very sturdy or rip-resistant! For durability and insulation value, I’d use plywood and paint it black, inside AND out. Actually, with the entire box painted black, what’s the point of using the dryer hose? Just having the 3-4″ hole at the top, feeding into the PVC pipe to the house, should be enough if the small return-intake pipe runs through the frame-board and down to near the bottom of the solar box so it isn’t trying to suck hot air out of the top of the box as well. The dryer-hose is sucking cooler air at the bottom of the box, then warming it as it goes up the hose, but omitting the hose would mean unobstructed flow of hot air up the outlet pipe. The box in the video would have a lot of hot air around the dryer hose that’s not going anywhere, just heating the inside of the box. Seems inefficient to me, but what do I know? I’ve never made anything like this.
How well does this work in cloudy weather? I doubt it’s much good on murky days, and of course not when it’s raining or snowing. I wonder if a small dryer-vent type flap mounted to the inside of the board in the window would be light enough for the hot air to push it open and vent around it? Then on cold cloudy days and at night, without the force of the rising hot air to push it open, the flap would close, preventing house air from exiting into the box. The flap would have to be VERY LIGHT, unless you could mount a very tiny (solar-powered) fan such as from inside a computer, in the box or in the outlet-pipe, that would likewise shut off when the conditions weren’t ideal for solar heating.
Spray paint the tubing flat black to get more heat. The silver reflects the sun. The Black will absorb it
Very creative and in an emergency where there is no heat, this is a cool idea.
I wonder if this could work for a greenhouse.
Only during the day, and my greenhouse gets too hot on sunny days anyway! I had a big one at 8,890 feet elevation on a north-facing slope in Colorado, with lots of shade-cloth inside, that would climb to 120+ on a sunny winter day, just from sunshine! I was in my little unheated greenhouse in NY yesterday, and even with one panel of shade-cloth on it, it was 60 inside. I’m rooting cuttings and starting tree and shrub seeds inside it, so I don’t want it hot inside during winter – they need cooler temps so they don’t break dormancy, then freeze to death.
Won’t work. Box with hose should be insulated. Opening the window means big space to outside between window sashes. As air passes through pvc will cool to cold tempetures. Single glass on hose box won’t keep cold out of box.
So How do you prevent cold air from coming in when the sun goes down and the temps drop into the teens or lower??
Stuff a sock into the outlet in the room…..
The heat in the chamber outside creates a draw or draft as the pipe heats up. When the chamber cools to room temp you no longer have air moving in the system. All you need to do is cap the ABS pipe or stuff a towel in it to avoid cooling the air in the house.