Would climate change reduce the negative impact of cool roof on the winter energy balance? Optimization study starting from monitored data on different roof types and weather zones

Existing research on reflective cool materials is manly focuses on the cooling demand, overlooking the necessity for annual energy optimization due to weight of wintertime penalties. To guide researchers in developing more reliable analyses under current and future weather conditions, this papers addresses the following challenges: adoption of innovative aerogel reflective paint, minimization of energy demand and emissions, reduction of discomfort hours and operative cost, impact of climate change. The paper starts by comparing surface temperature, reflected solar radiation and infrared emissions monitored on bituminous membrane, commercial cool product and innovative aerogel paint during wintertime in Mediterranean climate. Then, it delves into an optimization analysis for validated office simulation model by varying insulation level and construction technology into 6 European climates. Results indicate that in Mediterranean climates (Csa / Csb), the aerogel paint applied to wooden roof without insulation minimizes the cooling demand (-34% /-39%) reducing the operative emissions (-6% / -12%) and the operative costs ( -11% /-24%). In 2080, by adding 20 cm of insulation, the cooling demand and operative costs would decrease of-6% and the operative emissions of -5% in Csa climate. In Csb zone, ceramic paint and minimum insulation thickness would bring reduction of -12% for operative costs and cooling demand; the emissions will reduce of -10% also if the heating increases of +39%. In current and future Oceanic climate, aerogel combined with concrete roof and 20 cm of insulation assures reduction of cooling demand respectively of -7% and -6% with increment of heating demand of +2%. The operative emissions and costs can be reduced of -2%. Instead in Nordic climate, cool paints are not environmental and economically profitable. • Aerogel and ceramic reflective paints are numerically and experimentally compared • Results of wintertime monitoring campaign evidence the effect of reduction of heat gains • Optimization analysis is based on consumptions, operative emissions and discomfort hours • The interacting influences of reflectivity, insulation and roof technology are investigated • Mediterranean, Oceanic, Continental and Nordic actual and future climates are considered