Solar radiation mapping at the micro-urban scale using GIS

The paper describes the solar radiation mapping technique used in the application of ELaR, a methodology and integrated tools to support sustainable design options in rehabilitation projects. In particular the paper explains how Geographic Information Systems can be used to map the solar radiation incident on the roof and facades of existing buildings at the micro-urban scale and how such maps can help to facilitate the diffusion of passive heating and cooling techniques in the energetic/environmental upgrading of existing buildings. ELaR stands for Ecodynamic Land Register, a tool to help designer to evaluate sustainability through energy and material flows analysis (Daly H.E. 1990). The specific information system developed is based on the geometric structure of the land cadastre and allows to evaluate different design options in term of amount of input and output flows activated to sustain the activities related to building uses. From the practical point of view the methodology is based on the use of two specific synergetic tools: - A Geographic Information System, with the main aim to elaborate specific thematic maps, which represent the existing environmental conditions of the local area; such maps include information on potential local renewable resources and on the geometrical configuration of the existing buildings. Particular attention has been paid to the estimation of solar radiation incident on the facades and top of the existing buildings by using digital elevation models (DEM, raster resolution 0,5m / pixel). - Spreadsheets, linked to the thematic maps on the renewable local potential, to define the different design options in terms of input and output flows related to the land parcel where the building stands. These quantities are expressed in terms of specific impact indicators such as, the CO2-equivalent emissions, primary renewable and non-renewable energy.