BAU-R-3: Investments in the energetic refurbishment of building envelopes | Umweltbundesamt

BAU-R-3: Investments in the energetic refurbishment of building envelopes

Ever since the mid-2010s, investments in the energetic refurbishment of building envelopes – in other words, façades and insulations as well as exterior doors and windows – have been on the increase, both in residential and non-residential buildings. In 2020 and 2021, however, the development has also been affected by rising prices in the building sector. On the other hand, it is not possible to discern a significant trend in the two respective time series.

Energetic refurbishment supports the adaptation of buildings

Climate-compatible urban planning and design safeguarding the retention and enhancement of an urban green-blue infrastructure is one approach towards avoiding or at least mitigating heat stress. Other measures approach the issue by tackling the extant building stock. In order to protect interior rooms from overheating, active technical cooling methods are used in residential and working premises in warmer climate zones. During the hot summers of recent years, it was clear to see that this response was also applied in Germany. There was an exceptionally high sales volume in mobile air-conditioning units for active cooling in apartments and houses. It must be said, however, that the use of air-conditioning is associated with increased electricity consumption which, in turn, leads to increased CO2 emissions, unless the electricity mix is not largely derived from renewable energy sources. Such measures are therefore apt to run contrary to the efforts of increasing climate protection. In addition, the abstracted air from air-conditioning systems warms up the local urban atmosphere further thus exacerbating bio-climatic problems. Passive cooling measures should therefore be given greater priority both in refurbishing extant building stock and in the design of new builds.

As far as new builds are concerned, there are legal regulations contained in the German buildings energy act (GEG) in conjunction with various technical specifications such as DIN-4108-2:2013-02 on the minimum requirements for heat protection, with the aim to ensure that the interior delivers appropriate thermal conditions even under prevailing hotter climatic circumstances. In respect of older buildings this is – depending on a building’s age – not always the case. Whenever structural work is carried out in such buildings in order to improve a building’s energetic envelope, for instance by insulating its roof and façade and by fitting modern windows and exterior doors, these measures are usually combined with improving heat protection. This is due to the fact that carrying out such measures requires compliance with legal and technical regulations stipulated by the GEG or by DIN 4108-2:2013-2. Besides, the GEG requires compliance with minimum standards to be achieved when carrying out structural changes. In the course of carrying out the energetic refurbishment of roof and façade, climate adaptation measures such as additional exterior shading or greening of the building should be carried out at the same time.

The indicator illustrates the financial investments for residential and non-residential buildings, which are expended annually on energetic refurbishment of building envelopes. This indicator takes into account investments in products such as insulation of façade and windows / exterior doors, which usually reduce the heat loss of a building and improve its heat protection in summer. The data underlying the indicator are based on a special evaluation of the construction volume statement issued by the German Institute for Economic Research (DIW)¹⁴⁹. After a decline at the beginning of the time series, the mid-2010s experienced an increase in investments in the energetic refurbishment of both – residential and non-residential properties. Even though the time series has not been price-adjusted, and although the increase partly reflects the high prices resulting from a high demand for new builds and a scarcity of building materials, this development seems to indicate that measures are now increasingly implemented in respect of building stock thus benefiting – in addition to energy efficiency – summer heat protection and, in turn, adaptation to climate change.

In addition to summer heat protection, a wide range of other measures are required in order to equip new and extant buildings for the impacts of climate change. The structural adaptation of buildings in Germany is essential – especially in view of ever increasing extreme weather events such as heavy downpours or driving rain, storms and tornados, hailstones or snow loads. Such adaptation measures are essential, despite high standards of building design, construction technology and implementation. For this purpose, some buildings might allow the fitting of safety grilles and safety glass for protection from hailstone damage, in conjunction with an additional safeguarding of solarthermal and photovoltaic units or alternatively, the storm-proof incorporation of such facilities into the roof structure. Measures for protection from floodwater and heavy rain range from waterproofing buildings by means of fitting moisture barriers or waterproof concrete structures over drainage units or pumps, and backflow preventers in sewage systems. It is equally essential for such safeguarding measures to be considered, for instance, in the planning stage for new builds, so that they can be implemented from the outset e.g. by selecting particularly robust materials and employing more stable construction methods. Above a protection target, usually 30 cm above the design water level, more ecological and regionally typical construction methods can be used. In respect of extant buildings, the adaptation usually involves retro-fitting, for instance in the case of actively sealing cellars to protect them from water pressure – as a rule trickier and more expensive to achieve. Nevertheless, it is presumably possible to get a grip on climate-related problems even with regard to extant building stock. Basically, it is the responsibility of a principal commissioning the building, or its proprietor, to implement such construction measures with the aim to safeguard the building from climate risks.

^{149 - Gornig M., Görzig B., Michelsen C., Kaiser C., Klarhöfer K. 2020: Strukturdaten zur Produktion und Beschäftigung im Baugewerbe. Berechnungen für das Jahr 2019. Bundesinstitut für Bau-, Stadt- und Raumforschung am Bundesamt für Bauordnung und Raumwesen (Hg.). BBSR-Online-Publikation, Band 15/2020, Bonn, 44 pp. https://www.bbsr.bund.de/BBSR/DE/veroeffentlichungen/bbsr-online/2020/bbsr-online-15-2020.html}