Building Energy Simulation by an In-House Full Transient Model for Radiant Systems Coupled to a Modulating Heat Pump

Radiant heating coupled to a heat pump is a particularly energy-efficient system, recommended in new constructions. However, the potential energy savings associated with this high thermal inertia system can only be achieved with appropriate control laws, to be tested in a full building–plant simulation environment. The developed transient code concurrently solves three tailored dynamic models of each involved sub-system, namely: building envelope (a benchmark room defined by ISO 13791), radiant floor (designed in accordance with EN 1264-2), and heat pump (an air-to-water electrically-driven modulating unit). Different control strategies were implemented, such as variation of internal temperature set-point dead band, supply temperature to radiant panels, and heating modes. Among the examined variables, we found that the higher energy savings (up to 15%) can be obtained by a proper choice of the supply temperature: in particular, fixed supply temperature should be preferred to climate-based control for this case study. The developed model can be used for optimal design of new systems and associated controls and for accurate energy audits of existing buildings employing these technological solutions.