Solar thermal heating makes houses up to 67% more energy-efficient than a perfectly optimised building envelope. This is the result of a paper which compared the efficiency of solar thermal systems with building insulations. The study, which was commissioned by the German Federal Solar Industry Association (BSW Solar) and carried out by the German Sonnenhaus-Institut e.V. (Solar Houses Institute) and engineering firm Econsult, found that structures with a high solar thermal coverage are significantly more environmentally-friendly.
Example: A so-called “Efficiency House 70” with a combined pellet and solar heating, in which the solar thermal system covers at least 60% of the space heating and hot water demand, produced only 2 kg CO2 per year and square meter. The annual CO2 emissions of a passive house with a gas boiler and a solar thermal system for water heating were three times as high, with 6 kg/m².
