The case is one of the demonstration sites where the technologies developed within the H2020 project BUILDHEAT have been installed. The building is a large multifamily house in a small quarter in the outskirts of Zaragoza. It has 53 dwellings of two main sizes (i.e. 85 m² and 55 m²) distributed in 5 staircases on 4 floors. The building was constructed in 1988, is owned by Zaragoza Vivienda, the social housing Agency of Zaragoza, and is used for sheltered housing.
The main structure is made of structure with non-bearing brick walls and flat concrete roof. The initial quality of the envelope is quite poor, with no insulation and single-pane glass windows.
The heating system is based on electrical heaters, installed in each apartment, that supply hot water for both domestic use and for the radiators. Moreover, electrical radiators are also integrated to ensure the proper energy supply. Concerning the cooling, it is supplied in some of the apartments by single split units.
The average electrical consumption for each apartment, including lighting, appliances, heating and cooling, for every dwellers’ usage, i.e. lighting and appliances, ranges between 3,000 and 4,000€ per year.
Moreover, all windows will be replaced with double-glazed windows. Each dwelling will have a de-centralized HVAC system being run by air-air heat pump to cover the space heating and cooling, and DHW demands.
The renovation includes upgrades for both external envelope and HVAC system.
In particular, the envelope has been renovated through different solutions according to the orientation. In particular, the North façade has been simply insulated with 10 cm of External Thermal Insulation Composite System (ETICS – thermal conductivity 0.037 W/(m K)) and finished with a reflective coating. The South façade was designed to maximize the benefits from the sun. The insulation solution depend on the presence of the balconies and, where it is possible, it is made by ETICS, while the rest of the wall was insulated with rockwool insufflated in the internal chamber of the hollow brick wall.
The East and West façades was covered with the prefabricated elements developed within the project, that is a ventilated façade insulated with 6 cm of rock wool (thermal conductivity 0.034 W/(m K)) and further 10 cm of insulation (thermal conductivity 0.037 W/(m K)). The prefabricated elements integrate 16 photovoltaic panels that are connected to the heating and cooling system.
Concerning the system, the renovation foresees the replacement of electrical heaters and radiators with an air to air multifunction heat pump which can satisfy the domestic hot water (DHW) needs of dwellers as well as the thermal loads for air conditioning. A new false ceiling has been installed in the dwellings for integration of the new emission devices. The heating system is controlled by an innovative multi-control inverter (MCI), developed by the BUILDHEAT partners, that is able to manage in the most efficient way the power flux from the grid and from PV panels that are placed on the east and the west façade and on the roof. Each dwelling has its own PV panels and heat pump. In presence of an excess of energy generated by PVs compared to heat pump consumptions, the available energy is not fed into the grid, but stored into the storage to an electrical resistance in its storage able to reduce the on time of the compressor. This solution can have interesting application with the increase of renewable energy shares in the grid, since it is very cheap compared to traditional electrical storage.
Thanks to the renovation, it is estimated a thermal energy saving of around 75%, leading from 58.7 kWh/m2 to 14.9 kWh/m2, while the yearly electrical consumption will be reduced from 78.7kWh/m2 K to 24.1 kWh/m2.
Links and documents for more detailed information: