Performance evaluation of balanced heating and cooling with hydronic ceilings and floors

Abstract

Climate change increases the necessity of cooling demand in European housing. Systematic solutions in building planning and construction level are essential in order to avoid retrofit air conditioning units’ installations. Implementation of Low Temperature Heating and High Temperature Cooling with embedded water-based systems is gaining ground in large scale residentials projects, being already a standardised practise in the tertiary building sector. In all related systems, heat dissipation and absorption at low temperature difference to room temperature, respectively surface systems, plays a central role. Economically motivated, the combination of cooling with underfloor-heating or also heating with ceiling-cooling systems is evident. This paper analyses challenges related to the capabilities and performance limitations of these applications, concerning thermal comfort limits, potential condensation risks, system energy efficiency and reliable control strategies. The outcomes of static and dynamic heat flux simulations are presented, accompanied with a literature review and conclusions from post occupancy performance evaluation surveys of realised projects. Arguments for utilising the ceiling surface for heating and cooling predominate those of the floor usage. Furthermore, there are convincing results in favour of laying the pipes close to the surface of thermally activated building systems (TABS). Control strategies of these systems in residential building should be very simple and robust. For cooling, best performance is obtained by TABS permanently operating with a constant water flow temperature of 21°C. For heating, very simple zone thermostats, without any features of nocturnal temperature reduction or weekly schedules are sufficient. This works also supports the argument of extending the applicability range of adaptive comfort to buildings with hydronic mass activation as a system cooling.