Energy savings using sunspaces to preheat ventilation intake air: Experimental and simulation study

Abstract This paper investigates the potential benefits of sunspaces to preheat the ventilation intake air to reduce the energy consumption of buildings. When sunspaces are combined with a mechanical ventilation system, it is possible to easily introduce the preheated air into every space of the building, which is of great relevance for energy savings. A modular sunspace prototype was designed and built to analyze its real thermal behavior. After validating the simulation model with experimental results, different sunspace configurations were tested in a residential building for different climates. Our findings indicate that sunspaces can significantly improve the energy behavior of the building, but the savings depend on different factors. First and foremost, the effectiveness of these systems clearly depends on the climate. While in zones with little need for heating the sunspace use is not advisable, in colder zones the energy savings are substantial, even more if they are combined with heat recovery ventilation. In the coldest climatic zone in Spain, annual primary energy savings of 38.48 kWh·m-2 were achieved with the best sunspace configuration, which represents a heating saving of 58%. Results also reveal that inertia is not convenient when using heat recovery ventilation. Lastly, when choosing the size of the sunspace, as its efficiency depends on its size, not only total savings should be considered, but also the investment to be made and its return.