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posted: 1/6/2013 5:43 AM

How to make a build-it-yourself solar heater

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Q. I would like to use some free solar heating in a south-facing kitchen. I cannot afford to have a system installed professionally. What type of simple solar heater can I build myself for one room?

A. For a kitchen, I would recommend building a simple solar window heater. With the cooking appliances, dishwasher, refrigerator, etc., which also generate heat, a solar window heater many provide enough extra heat so your kitchen actually becomes a net energy producer for your house.

A solar window heater works on the principle of hot air naturally rises because it is less dense than cold air. This draws room air in the solar window heater chambers to be warmed without the use of an electric fan. If you can afford a solar cell panel, a 12-volt fan could be attached to the heater.

The basic design concept of a solar window heater is a shallow insulated wooden box with a clear top. It is mounted in a window and tilts downward so the lower end rests on the ground. It should be close to the width of the window and any length. If you happen to have an old glass storm door or window panes available for the top, make the box that width.

A longer one has more clear top area exposed to the sun so it captured more solar heat. For any do-it-yourself projects like this, it usually best to select dimensions in multiples of four feet for best utilization of standard eight-foot lumber, insulation and clear sheeting.

There is a horizontal divider inside the box to create an upper and a lower chamber. The divider is slightly shorter than the box creating a gap at the bottom which connects the upper and lower chambers. The divider also functions as the solar collector panel to heat the air inside above it.

When this box is mounted in the window, the sun shines down through the clear top onto the divider/collector panel. This panel and the air in the upper chamber gets hot and less dense. Since hot air rises, the solar-heated air flow up the top chamber to the window and out into the kitchen.

This upward air flow draws cool room air into the lower chamber at the window. This air flows down to the gap at the bottom of the divider/collector and up to the top chamber to be heated and back into the kitchen. It helps to install small deflector panels on the open window end to keep the already solar-heated air from being drawn back into the heater.

To improve the effectiveness and heat output from the solar window heater, line the inside of the box with foil-faced rigid foam insulation. This reduces heat loss from the room air as it flows in the lower chamber. Face the foil toward the interior and paint it flat black to absorb more solar heat.

Install tight-sealing doors on the open end in the kitchen window because you must close off the chambers at night. If you do not, the air flow will run in reverse and actually cool your kitchen at night.

Q. We want to lower our electric bills. Our son keeps his computer on 24/7 because he says it will last longer and costs only a couple cents per month. Does a computer use much electricity and will it last longer?

A. The amount of electricity a computer uses depends upon its type, age and number of peripheral components it is powering. If it is left on 24/7, newer ones go to "sleep" to draw less electricity, but still draw some.

There are moving parts in a hard drive and the fan, so it will wear out quicker the longer it runs. Also, the longer it is on, the chances are greater that a large voltage surge or numerous small ones may harm it.

• Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit

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