Based on a structural renovation scale according to the BEG 40 EE standard (German federal funding scheme for making buildings energy efficient), coupled with outdoor air or geothermal heat pumps, and taking into account a less extensive renovation scale for listed buildings, three target years for climate neutrality were defined in line with the city's goals and resolutions - 2030, 2035 and 2045 - thus defining annual renovation rates between 4 and 11 %.
According to the calculations, all three renovation scenarios combined with photovoltaic systems on the building roofs achieve climate neutrality. However, for this, nearly all suitable roof space must be used. The scenarios differ in the size of PV surface area required, the amount of investment & planning costs and cumulative energy costs, as well as in the greenhouse gas emissions arising from gray energy (production, maintenance and disposal of building structures and installation technology). An earlier target year means renovating a higher number of buildings each year (with implications for the need for tradespeople and municipal jobs) and higher annual investment costs but, most importantly, a greater overall reduction in greenhouse gas emissions.