Evaluation of building wrapper performance by means of exergy method (plenary lecture)

Among the objectives of the Directive 2002/91/EC, the building wrapper represents a very important building subsystem to control energy dispersion and consumption. The Architect should be able to change the wrapper energy performance in order to control energy consumption. How to value and compare this energy dispersion with exergy analysis? Building wrapper should satisfy two tasks: - to reduce energy dispersion during winter time (especially in northern European buildings), - to guarantee thermal phase displacement during summer time (especially in southern European buildings). In Mediterranean area both task must be satisfied all over the year. The project calculates thermic isolation and phase displacement (of walls or windows or other building wrapped subsystems) in relation with energy transfer. In this paper we propose to calculate an energy valuation of building wrapper energy transfer. Heat exergy through wrapper transfer depends on temperature gap and heat transfer. Heat flow through walls depends on thermo-physics characteristics of the material. Heat exergy transfer could be used to evaluate an exergy flow through walls, and we can settle an exergy index to compare different walls. We could correlate thermo-physics parameters with heat exergy transfer and isolation heat flow through wrapper.