Geometric and thermal characterization of buildings at urban scale based on open data

Laburpena

The energy renovation in buildings is one of the major challenges for the decarbonization of the building stock. In order to prioritize decision-making in the choice of the most efficient solutions, it is necessary to characterize the behaviour of the building stock and measure the impacts of possible improvements at urban scale. Reaching that point of definition requires setting geometric and thermal characteristics of the stock. In this study, a methodology is developed for the geometric and thermal characterization using open data (such as cadastral data) that is processed through QGIS (Free and Open Source Geographic Information System). Thus, this study aims to define, in a systematized and sufficiently precise way, the geometric and thermal characteristics of buildings at urban scale to feed later an energy demand model that evaluates the potential for improvement and mitigation through different actions. This geometric characterization is based on obtaining and processing open data from cadasters to extract, using QGIS, the envelope surfaces by orientation that define the stock. Through the geometric data, the roof surface and the façade and windows surfaces by orientation are obtained. This information contributes to define later the overall thermal conductance (UA) and the south equivalent surface (SES). In the case of thermal characterization, an automated process is defined, by means of assigning different parameters according to the construction year of each building known from cadastral data. The parameters obtained are; a) U values (to determine the thermal transmittance of each element); b) the g solar factor of the glazing (to determine the solar gains); c) the air renovation due to ventilation and infiltration; and d) the internal gains. The methodology is applied in a real case study for a given area in Bilbao and the values of the parameters obtained through QGIS are validated with those presented in energy performance certificates.