I³MS - Blocken Seminar
Prof. Dr. Bert Blocken - Computational Evaluation of Climate Adaptation Measures in Urban Areas
Even if actions for mitigation of climate change would be immediate, extensive and fully effective, a certain degree of climate change would be unavoidable due to lack of mitigation actions in the past. Its impact should be limited by climate change adaptation, i.e. adapting to its consequences. This presentation focuses on climate adaptation of cities and buildings to heat waves. It presents results of the computational evaluation of climate change adaptation measures, focused on the reduction of outdoor temperature and on the reduction of indoor temperature.
Concerning the outdoor environment, vegetation is often contemplated as a viable and effective adaptation measure against heat waves. To investigate its potential for reducing outdoor temperature during heat waves, a case study with Computational Fluid Dynamics (CFD) was conducted for a street canyon in the center of the Dutch city Arnhem. First, a double validation study was conducted based on available measurement data. Next, the case study was performed for the meteorological conditions of an afternoon hour on a hot summer day during a heat wave with wind of speed 5.1 m/s at 10 m above ground and direction along the canyon. Different scenarios were analyzed: no vegetation, avenue-trees, facade greening, roof greening and all trees, facade and roof greening combined. The results highlighted some important misconceptions, indicating that some increasingly popular adaptation measures might be much less effective than often assumed.
Concerning the indoor environment, we analyzed the effectiveness of six passive climate change adaptation measures applied at the level of building components using building energy simulations for three generic residential buildings as commonly built in - among others - the Netherlands: (1) a detached house; (2) a terraced house; (3) an apartment. The study involved both residential buildings that were built according to the regulations and common practice in 2012, and residential buildings that were constructed in the 1970s, with a lower thermal resistance of the opaque and transparent parts of the building envelope. The climate change adaptation measures investigated were: (i) increased thermal resistance; (ii) changed thermal capacity; (iii) increased short-wave reflectivity (albedo); (iv) vegetative roofs; (v) exterior solar shading; and (vi) additional natural ventilation. The performance indicators were the number of overheating hours during a year and the amount of energy needed to keep the indoor air temperature within acceptable limits. The results indicated that some of the most expensive measures are least effective, while the cheapest one has the largest beneficial effect.
Given the complexity of the heat and mass transfer processes involved, the above-mentioned studies demonstrate that computational evaluation is imperative to assess the potential of climate adaptation measures, both for the outdoor environment and the indoor environment.