That is the record reported by Axel Gedaschko, chairman of GdW, the largest German federation of real estate companies, representing 6 million homes and 13 million inhabitants.
In a report published last year, the GdW noted that more than 340 billion euros had been invested since 2010 in the energy renovation of buildings to reduce energy consumption by 15%.
These renovations, supported by the public investment bank KfW with up to 13.5 billion euros, included replacing windows, new heating systems, and facades' insulation.
However, despite the huge investments, the results were not very optimistic. Energy consumption remained relatively the same without significant changes, between 1990 and 2010, consumption decrease by 31% in Germany. After the energy renovation campaign started in 2010, consumption has remained stagnant, according to GdW.
In 2010, a household consumed an average of 132-kilowatt hours of heat per square meter. In 2018, it consumed ... 130.
As the rest of Europe continues to embark on an ambitious energy renovation plan for buildings, it seems relevant to look into this large-scale feedback.
The GdW highlights several causes for the stagnation of consumption.
First would be the famous "rebound effect." In better-isolated housing, occupants would have improved their comfort by increasing the heating setpoint. We are adding to that the renovations that were probably inefficient.
"We need to move away from increasingly expensive energy retrofits and insulation and opt for decentralized energy production using digital techniques to avoid emissions." Said Gedaschko.
The GdW study does not give details of the "rebound effect." It seems to be more of a hypothesis on their part than an observation. An American study carried out in 2018 on 30,000 homes in Michigan precisely sought to observe this post-renovation "rebound effect." Its findings are that the occupants did not change the temperatures in their homes significantly. There was no rebound effect.
In my opinion, the recommendation to stop the insulation work as suggested by the GdW seems incorrect. It seem necessary to me to complete this study by observing all the significant variables:
- Impact of new uses (household appliances, electronics)
- Changes in occupancy density,
- Changes in behavior (setpoint temperature for heating, opening windows, etc.)
- Quality of insulation work.
Throwing out the insulation work in buildings seems to me to be more than dangerous in the quest to decarbonize an industry that represents more than 35% of global energy consumption.
Mr. Gedaschko also recommends "opting for decentralized low-carbon energy manufacturing, with digital emission avoidance techniques." This is the concept of a microgrid.
The GdW proposes strengthening local renewable energy production and modulating consumption according to the availability of energy (solar and wind are by nature intermittent). It is then necessary to connect the energy-intensive technical systems to control them according to the network's capacities. This proposal is part of a fundamental trend of better measuring and optimizing the technical equipment of buildings.
Wattsense, which makes it possible to connect and control buildings easily, aims to sustain energy consumption reductions at costs drastically lower than insulation work. The recommendations made by Mr. Gedaschko, therefore, go in our direction. Even so, my 15 years in the HVAC (heating, ventilation, and air conditioning) industry have taught me that the quality of insulation is an essential component of a thermodynamic system's performance.
Each sector must make its contribution to decarbonization. For buildings, there is no opposition between digital solutions and insulation. On the contrary, the two are complementary and reinforce each other. Thanks to the digital technology deployed in each building, we can determine an insulation operation's performance and identify improvement options.