Radiant cooling and ventilation strategies in low energy buildings

In mild climates due to the increase of request of comfortof people there is a growing number of installation of low cost and low efficient cooling system even in new buildings. In designing low energy buildings it necessary nowadays to consider this trend and offer proper solution (envelope and plants) able to reduce the consumption of primary energy. An interesting solutioncapable to guarantee high levels of comfort is the control of surface temperature of wall and slabs (both from the envelope and plant side) because acts mainly on radiative heat transfer between human body and the indoor environment. This approach recours to cool surfacesand the role of ventilation in terms of comfort and condensation risk became essential. The study presentedhere is focused on this topic and has the aim to investigatethe techniques of ventilation (natural, mechanical or hybrid) in order to reduce the use of energy and at the same time to guarantee a good level of comfort for the inhabitants using geothermal inertia. The outcome of this study are simple diagrams able to guide the designerin choosing the right strategy according to externalclimate (a coupled concept for radiant cooling and ventilation). The sensitivity of the selected strategy in respect of the boundary conditions (internal loads, thermalmass, shading coefficient etc) is also presented. All the results are based on dynamical simulations sufficientto represents the more reliable strategies for a city in a mild climate where both heating and cooling season (even with high level of humidity) are important.