COPYRIGHT 2017 JAMES DULLEY ( www.dulley.com/sea/ ) - January 2017 - (graphics ref. No. 145u at www.dulley.com/sea/column/2017-jan.htm ) "Build a simple solar window heater project with your kids" Dear Jim: My kids are studying solar energy and they want me to help build a solar heater for their play room. What is the simplest solar heater design that will actually provide heat for their room? - Paul M. Dear Paul: This sounds like a wonderful project for your children and you to learn about solar energy and conservation and it will actually lower your heating bills. By adding an extra small hinged door, it can also ventilate their room during summer. To keep the design and construction simple, building a passive solar window heater is your best option. On a sunny winter day, the amount of free solar heated air flowing out can be as much as from a typical electric heater. A solar window heater utilizes the concept that warm air is less dense than cool air. Cool room air is drawn in the bottom of the solar heater. As the air is heated by the sun, it naturally flows up and out into their play room. It is called passive solar because it does not use electric fans to move the room air through the solar heater. If you want to get fancy, add a small 12-volt solar cell panel and fan to move more air through the (active) solar heater. A solar window heater is simply a long shallow wooden box with a slightly shorter horizontal divider/collector inside. This creates upper and lower air flow chambers connected at the bottom for air flow through them. The top is covered with a clear acrylic sheet or glass from an old storm door so the sun shines in to heat the divider/collector. The top end of the box is open and is sealed with weatherstripping in the window. As the sun heats the divider/collector and air in the upper chamber, it flows out into the play room as it draws cool room air in the bottom chamber. This flow of heated air continues as long as the sun is shining. After the sun goes down or on cloudy days, close the window to stop the air flow. To simplify construction and reduce the material cost, make it two feet wide and either four or eight feet long to best utilize standard lumber. A total depth of the box of about eight inches is adequate for two four-inch high air flow chambers. Attach several strips of 1/2-inch aluminum angle to the divider/collector and paint it flat black to absorb maximum most solar heat. The angle strips provide more solar surface area and create air turbulence for better heat transfer. It is important to line the entire box with 1/2-inch rigid foil-backed urethane foam insulation to minimize heat loss. Paint the exposed foil backing in the upper chamber flat black, but leave the lower chamber foil unpainted. Use adhesive-backed foam weatherstripping to seal the clear top to the wooden box. Build the end that mounts in the window so the clear top is tilted at about 45 degrees. This provides a good balance between solar heat gain and air flow volume for maximum heating. It can be mounted on any side of the house other than north, but the south is most effective. If you want to use it during summer to ventilate their room, put a small hinged door near the top. Open the door and block the hot air outlet into the window. The solar heated air will flow out the hinged door outdoors. This draws room air in the bottom opening creating a free exhaust window fan. Dear Jim: My house has settled some over the years and there is a fairly wide and deep crack around one door frame. When I caulk to seal it, how far down in the gap should I push the foam backer rod? - Karen D. Dear Karen: It is best to use a foam backer rod for a deep wide crack instead of attempting to fill the entire crack with caulking. Push the backer rod in to a depth (measure where the edge of the rod touches the sides of the crack) equal to the width of the crack. Use silicone or polyurethane caulking. Polyurethane takes longer to cure than silicone, but it can be painted. Siliconized acrylic caulking is another paintable option. Send inquiries to James Dulley, Publication Name, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com.