Roof gradient for more thermic yield in winter

Context description : sun solar collector suncollector solarcollector collectors suncollectors solarcollectors termal thermic energy sunenergy solarenergy power sunpower solarpower roof roofs gradient gradients winter optimized yield
zeroenergy nullenergy house zeroenergyhouse nullenergyhouse solarhouse sunhouse houses zeroenergyhouses nullenergyhouses solarhouses sunhouses Austria Austrian south east Styria Styrian near close to Radkersburg Bad Gleichenberg Halbenrain event events date time century 20 year 1998 98 high resolution Photo Photos pic pics picture pictures JPG JPEG