June 17, 2025, 4:30 am | Read time: 3 minutes
When it comes to energy-efficient renovations, the order of steps is often unclear. Should you start with replacing the heating system, or is it better to begin with insulation? Experts offer advice on the sequence.
Choosing to retrofit your old house for energy efficiency is the right decision–it pays off. “Savings of at least 50 percent of the previous energy demand are possible,” says Alexander Steinfeldt, spokesperson for the nonprofit advisory company co2online. If a building meets the passive house standard, it can even be 100 percent. However, the measures required are expensive–too expensive for many. Especially too costly to tackle multiple points or everything at once. So where is the best place to start, and which steps might be postponed for several years? What is the ideal sequence for energy-efficient retrofitting?
There Is an Ideal–but Not for Every Case
The answer to which order to follow for energy-efficient retrofitting can vary from house to house and also depends on the owners’ budget, including currently available government subsidies.
Nevertheless, there is generally an ideal order for energy-efficient retrofitting: first insulate the roof and facade, then update the heating system. Insulation changes a building’s energy needs. The heating system’s capacity can only be perfectly matched once the demand is known.
A factor that argues against the ideal is the age of a heating system. “If the heating system is, for example, 35 years old, the likelihood is quite high that it will fail in the foreseeable future,” says Andreas Skrypietz from the German Federal Environmental Foundation (DBU) in Osnabrück. It then makes sense to first renew the system, even though it cannot yet be calculated how high the demand will be once insulation measures are implemented.
The good news: “Today’s heating systems have a performance range in which they can be used without loss,” explains Skrypietz, who leads the DBU initiative “Future at Home–Sustainable Retrofitting.” His advice, considering ongoing political discussions and regulations for gas and oil heating systems: “One should definitely install a heating system based on renewable energies right now.”
Energy Consultants Secure Government Subsidies
Homeowners can get an initial overview of what needs to be done to their building through the modernization check from co2online. But for concrete planning and implementation, an energy consultant must be hired. They assess which measures are sensible and where the most savings potential lies, and they develop an individual retrofitting plan for the house.
The planning spectrum ranges from individual measures such as replacing windows, renovating the roof, or using renewable energies for hot water production or electricity generation to complete retrofitting. Important: “Without an energy consultant, you won’t get a loan from the Kreditanstalt für Wiederaufbau (KfW) and, in most cases, no subsidy from the Federal Office for Economic Affairs and Export Control (Bafa),” says Alexander Steinfeldt. The costs for energy consulting are covered up to 80 percent by Bafa.
The energy consultants listed at energie-effizienz-experten.de have committed to providing neutral and independent advice. Here you can find a nationwide directory with around 13,000 experts for energy-efficient building and retrofitting from the German Energy Agency (dena). They are also authorized to submit funding applications for retrofitting measures on behalf of their clients.
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Steinfeldt advises also asking homeowners who have already retrofitted their homes for energy efficiency for recommendations. This also applies when searching for qualified craftsmen. “Particularly important is product-neutral and trade-independent advice,” advises Klaus-Jürgen Edelhäuser, board member of the Bavarian Chamber of Civil Engineers.
With material from dpa