Climate optimised building parameters for low energy summer comfort under a discomfort index

An in-dept analysis of a large office building built in the 60s (occupied by the Italian Ministry for the Environment, chosen for its representativity of buildings built in the 50s and 60s) has been performed. A software model of the building has been created and used to simulate its behaviour in the climate zone of Rome, using a dynamic simulation software. Then a building with the same geometry and same internal gains but with higher storage mass (m > 350 kg/m2, calculated with the method of Heindl ISO 13786, 1994), selective glazing (U value of windows < 1,8 W/m2K), movable external blinds (solar factor: g < 0,15) and a simple night ventilation strategy has been simulated and optimized to achieve good comfort conditions at low or no energy consumption for mechanical cooling. Blinds have been designed and simulated to obtain required shading without penalizing daylighting. We calculate the values of the thermophysical parameters which minimise a discomfort index. elaborated starting from the PMV scale of Fanger. Comparison of the original buildings to the optimized buildings shows: - a 85% reduction of discomfort index supposing the buildings are not air-conditioned; - a 30% to 80% reduction in energy consumption for cooling supposing the buildings are air-conditioned. A consequent reduction of greenhouse gases emission up to 70100 tCO2-eq/year. The analysis leads to a proposal for municipal building codes optimized to the climate zone, where the installation of air conditioning is allowed, in new buildings or large retrofits, only if certain target values are achieved by the building envelope and structure.