HeatResBuild

The overheating risk in buildings continues to increase due to the advancing global warming and the increasing sealing in cities. However, the current state of research still shows numerous uncertainties regarding the assessment of overheating in buildings. For example, there is still no internationally uniform standard on how to assess the overheating evaluation of residential buildings. Even the standard that applies in Germany, the DIN 4108-2, does not take into account some relevant factors in its assessment of summer thermal insulation. Furthermore, most scientific work concentrates on case studies for a specific location without making a spatial comparison between urban and rural areas or between different regional climates within a country. The interaction between heat adaptation measures in open spaces and buildings is also insufficiently researched, as are the reasons for the observed low implementation dynamics of climate change adaptation measures. The HeatResBuild project aims to address these relevant research gaps in connection with the IOER research projects HeatResilientCity, Klimakonform and SYSDYM and to develop approaches to solutions.

In the HeatResBuild project, overheating of buildings is investigated from several perspectives and the following focal points are examined:

1. By applying the model chain from microscale urban climate simulation (carried out by the partner TU Dresden and the UFZ) to building performance simulation (see figure below), it is analysed to what extent cooling effects of heat adaptation measures in the open space affect the overheating in buildings. The opposite direction, to what extent measures on the building side affect the micro-scale urban climate and thus ultimately also the building comfort, can also be illuminated with this approach as well. Example neighbourhoods in this project are the German cities Dresden-Gorbitz, Erfurt Oststadt, Plauen Südostvorstadt and Naumburg Altstadt. This part of the project is done in cooperation with the HeatResilientCity II and the KlimaKonform project.
2. The impact of different regional climates and the heat island effect on overheating in buildings is investigated using an approach in which meteorological measurement data from the German Weather Service over the last 30 years is statistically evaluated for six different locations in Germany. For each location, an average summer over the last 30 years is determined, as well as a future average summer in 30 years using climate projections. In addition, the urban island effect (carried out by the partner TU Dresden) is examined for the different locations to determine to what extent the overheating in the building differs depending on whether it is located in the city or on the countryside. The effect of the different meteorological data sets on overheating in the building is evaluated by means of building performance simulations. This topic is being worked on in cooperation with the HeatResilientCity II project.
3. While several indicators for the evaluation of overheating in buildings exist, their significance is limited. Building on these existing indicators, the evaluability of overheating in residential buildings is to be improved and more precise scientific but also practical indicators developed. This topic is also being worked on in cooperation with the HeatResilientCity II project team.
4. The implementation dynamics of heat adaptation measures in open spaces and on buildings is currently very low in practice. The causes of this low dynamics are to be researched using system dynamic approaches based on the SYSDYM project.

In the HeatResBuild project, overheating of buildings is investigated on different focal points:

Which sets of indicators can be used to assess overheating in buildings appropriately, both scientifically and in practice? How can a link to health effects be established?

Is a building that is heat-resilient in Dresden also heat-resilient in other German cities such as Hamburg or Stuttgart? How great is the influence on overheating of dwelling whether the building was constructed in the city centre or in the surrounding countryside?

What effects do heat adaptation measures in open spaces have on the overheating intensity in buildings and vice versa?

How can the implementation dynamics of adaptation measures against summer heat be significantly increased?

First results

Model chain urban climate simulation - building simulation
The previously developed model chain of urban climate simulation to building performance simulation (1) was significantly extended. In a scientific publication submitted together with the TUD and the HTW, the limitations of this model chain and possible alternatives were discussed. The heat adaptation measures in the open space of the two neighbourhoods considered in the urban climate simulation, Dresden Gorbitz and Erfurt Oststadt, were finally agreed upon. These will now be implemented in the urban climate simulation and their effects on the indoor climate of the building will be analysed by building performance simulations.

Effects of the regional and urban climate on the heat load in the building
The room-by-room 3D simulation models of two multi-family house types (“Gründerzeit” architecture and prefabricated buildings) were created and parameterised, and representative (average) summer months for six different locations in Germany were conducted from the DWD data records of the last 30 years. In the next step, the imprinting of the heat island effect to consider buildings within the city will be implemented. In addition, meteorological data sets of projected warmer summers in the future will be created. Some of the more than 100 simulation variants have already been started and must be vividly prepared at the end.

Indicator development overheating in buildings and health aspects:
In connection with the HRC II project, cooperation with the HTW was carried out on the creation of a practice indicator as well as on the further development of a scientific indicator set based on existing indicators.
The practical indicator evaluates the overheating risk of rooms as well as the effect of different heat adaptation measures in a qualitative way using a five-part traffic light system. The assessment is based on the findings of previous building simulations and monitoring of the indoor climate. The practical indicator serves as a first (rough) assessment and addresses interested citizens rather than expert planners. It is not a substitute for planning or more detailed observations through building simulations. This practical indicator is to be translated into an online tool in the HRC II project after successful testing by practical partners in the state capitals of Dresden and Erfurt in 2022.
The scientific indicator set is based on the existing indicators of the overtemperature degree hours of DIN 4108-2 and expands this to include room utilisation, consideration of sultry events and, above all, the adaptation of humans to changing temperatures in summer. In 2022, this is to be presented and discussed with representatives from planning practice.
In a further step, literature research will be conducted to determine whether the state of the art in science and practice is sufficient to establish a link between indoor heat stress and health stress via the scientific indicator set. This research has been started in the last months and will be deepened significantly.

System dynamics modelling for the implementation of adaptation measures
In connection with the SYSDYM project, joint modelling (Group Model Building) workshops were held with actors from science (TUD, IÖR) and practice (housing cooperatives EWG Dresden and WBG Zukunft) on the topic of the low implementation dynamics of building greening. For this purpose, causal loop diagrams were created in four workshops, which showed the interdependencies of the factors that influence the implementation dynamics.

Literature
(1) Schünemann, C.; Ziemann, A.; Goldberg, V.; Ortlepp, R.: Urban climate impact on indoor overheating – a model chain approach from urban climate to thermal building simulation. In Proceedings of the Proceedings of 26th International Sustainable Development Research Society, Budapest, Hungary, 15.-17.07.2021, 2020.