Twinsolar: price+value = eligible!
Due to our new prices, the collectors are now cheaper than a good flatscreen and they are subsidized in various countries - for example in Germany with 90€/m². So all you need is a good place where the collector can capture the radiation of the sun and the solar ventilation can begin.
Only once a year you have to change the filter, otherwise the collector is maintenance free. The system operates self-sufficiently.