Solar houses good for climate

To install a solar thermal heating system can make a house by 67% more energy efficient than to introduce a maximum optimized building envelope. This is the result of a study commissioned by the German Solar Industry Association BSW-Solar. According to the BSW, the study was the first to compare the efficiency of maximum insulation and solar thermal energy as means to reduce a house’s CO2 emissions. The study conducted by Econsult states that buildings with a high solar coverage rate of their energy consumption are significantly more climate friendly than houses without solar installations that have introduced extensive insulation measures. The authors argue with the example of a KfW 70 house – this standard means that due to thermal insulation measures a house requires 30% less heating energy if compared to a new standard building of that class – combining pellet and solar heating, where the solar heating system covers at least 60% of the space heating and hot water needs. Such a house according to Econsult produces 2 kg of CO2 emissions per square meter of living space and year. The CO2 emissions of a passive house with a gas boiler of similar size and a solar system for drinking water for comparison emits 6 kg of CO2 per year and sqm of living space. “That’s three times the amount”, the authors write. Jörg Mayer, Managing Director at BSW-Solar, concludes that “solar thermal heating concepts with high solar fraction values can save much more carbon dioxide emissions than the energy efficient buildings supported by the German federal government today. If houses with high solar energy coverage would be supported by the state in the same way as the energy-efficient houses, the government could reach their ambitious climate protection goals much more efficiently.” The comparability of the efficiency of different house types was secured by using the same conditions and calculation standards. These include construction costs, energy prices and consumption as well as user behaviour. “The study is a basis for an objective discussion of the innovative and energy-efficient construction in the future - even against a background of higher delivery efficiency,” notes Peter Rubeck, co-author and Director of the Bavaria-based Sonnenhaus-Institut. “For the first time it has been possible to evaluate efficiency in different kinds of buildings, in a sense of comparing apples to pies.” The study examined three categories of buildings defined by the Kreditanstalt für Wiederaufbau (KfW development bank) – the energy-efficiency „KfW 70” , the “KfW 55”, and the “passive” house standards. Within the study, each of the types was equipped with four different kinds of systems to secure heating and warm water supply: from floor heating combined with condensing gas boilers and solar systems, through ventilation systems with heat recovery, solar systems with standard fraction and pellet heating up to solar panels with 60% solar coverage rate and pellet stove.

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