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My son and I built a passive solar heater for a science project. I have researched it and I can't find what we did wrong… It is hot when you stick your hand in vent but is not blowing it out. The only thing I can think of is its a lot smaller then the window bc its against a glass sliding door. Would that make a difference???

I am sorry for being so late in replying. I was in Australia and could not use my forum then.

If you have a fresh air inlet at the bottom, back side and a hot air outlet on the top front side then air will naturally flow. It will now blow with any force but a bit of tin foil will move gently as it heats up.