Assessing thermal comfort in urban environments using a integrated dynamic microscale biometeorological model system

The interactions between the urban thermal environment and the human body are of a complex kind: On one hand, the microclimate conditions in cities are very heterogeneous in space and time, on the other hand the response of the human body to variable thermal loads is a complex system depending on a lot of different parameters, especially if movement inside the structures is considered.

The coupled numerical model system ENVI-met will be presented, which is able to calculate the microclimate conditions with respect to different building structures, surface materials and vegetation as well as the effects on humans moving around inside the structures.

ENVI-met consists of a three-dimensional non-hydrostatic microclimate model which provides the microclimate conditions and a two-node human energy balance model which calculates the response of the human body on the predicted conditions.

It will be shown, that such a dynamic model systems can give a more detailed analyses of thermal conditions than conventional steady-state models such as PMV. For example, it is possible to consider "memory-effects" of the human body: After being exposed to direct sun over a longer time, thermal comfort is still low, even after reaching shaded areas. In contrast, temporary shading can have benefits even when walking through unshaded areas, as the total thermal load of the body remains below a critical value.