EVALUATION OF BUILDING ENVELOPE RETROFIT TECHNIQUES FOR REDUCING ENERGY NEEDS FOR SPACE COOLING

One of the fastest growing sources of new energy demand is space cooling. According to EU-studies a four-fold growth in air-conditioned space is likely to take place between 1990 and 2020. The energy savings achievable in the end-use space cooling depend on a number of variables related to the building envelope, the plants and to some extent the behaviour of occupants. They are hence complex to evaluate and consequently often underrepresented in energy efficiency programmes and National Plans. This paper is based on some preliminary results of the IEE project KeepCool 2. It discusses in particular: a methodology for bottom-up assessment of the energy • savings related to “sustainable summer comfort” solutions; reference base case building typologies are analyzed in 5 European climates, and dynamic simulations are used to calculate the reductions in the energy need for cooling which can be achieved by specific retrofit actions (e.g. additions of effective solar protections, increased thermal insulation, night ventilation, increase of active mass by PCM, low solar absorbance surfaces,...); situations where mechanical cooling can be avoided are evaluated using the Adaptive Comfort model, according to the norm EN 15251. case studies of buildings with good summer comfort and • low energy consumption performances, according to the ten steps of the KC2 procedure. the analysis of case studies of “comfort policies” adopted by • public and private bodies to ensure summer comfort with low energy consumption (commitments to give priority to heat load reductions instead of introducing mechanical cooling, relaxed dress codes, low thermal insulation chairs, local air velocity increase). Introduction One of the fastest growing sources of new energy demand is space cooling. The studies EECCAC and EERAC predict a fourfold growth in air-conditioned space between 1990 and 2020 (Adnot, J. et Al, 2003). The IEA Future Building Forum even named cooling as one of the fastest growing sources of new energy demand (International Energy Agency, 2004). In its preamble, the European Energy Performance of Buildings Directive (EPBD) states that “Priority should be given to strategies which enhance the thermal performance of buildings during the summer period. To this end there should be further development of passive cooling techniques, primarily those that improve indoor climatic conditions and the microclimate around buildings” (European Communities, 2003, p. L1/66). But such passive cooling technologies, which are already available and cost effective (such as use of well designed sun shades, efficient lighting and office equipment, passive cooling via thermal exchange with the ground, night ventilation etc.) are not widely used on the market today: the most common choice for a building owner when addressing summer comfort issues is still mechanical cooling, often without previously investigating other available measures regarding the optimization of envelope features (e.g. solar protections, glazing solar factor,