Though we've covered lots of Passive Houses, a project in Stuttgart, Germany, claims to be the "first fully functional Active House in the world." Aktivhaus B10 is said to use "active measures" such as self-learning and automation to improve its energy performance.
First to deal with the terminology. A certified Passive House is one that demonstrates highly efficient energy performance to a prescribed standard, in particular in relation to its heating and cooling system(s), air tightness and approach to ventilation. It is a widely recognized and well respected mark.
A lesser known Active House vision and specification is set out by the Active House Alliance. Its principles focus on creating houses that afford healthier and more comfortable lives for their occupants, run on electricity supplied entirely by renewable energy sources and have "a positive impact on the environment."
The architect firm behind Aktivhaus B10, however, has created its own definition of the term Active House, which it says is protected by trademark law. By Werner Sobek's definition, an Active House is one that offsets its annual total energy consumption in a sustainable manner, anticipates and reacts accordingly to relevant changes both inside and outside the house and continuously measures and optimizes all energy streams.
Active Houses, it says, use no energy derived from fossil fuels or nuclear energy and generate sufficient energy for their own needs alone or by being networked with other such units. The mark is said to be characterized by this self-sustainability, by a lack of methods stipulating how that should be achieved and by its own evolution. It is to this specification that Aktivhaus B10 has been created.
Aktivhaus B10 is part of a research project exploring how materials, design and technology can extend home sustainability in an increasingly built-up world. The project is being run by E-Lab Projekt, a subsidiary of the non-profit Stuttgart Institute of Sustainability (SIS) that promotes and develops methods and technologies for sustainable building.
The house itself is a single-story building covering around 90 sq m (970 sq ft). It produces around 200 percent of the energy it requires and uses the surplus energy to power two electric cars, two electric bikes and the house next door. Electricity is generated by a photovoltaic array. Werner Sobek says the aim of the house is not to maximize surplus energy, but to reduce its load on the grid by predictively deploying energy as required.
Energy consumption is kept to a minimum by the building's high thermal performance. It is heated and cooled using a heat pump, with a solar array and ice storage tank as heat sources. The only other energy used for heating and cooling is generated from the building's photovoltaic array and used to power the pump.
In addition, Aktivhaus B10 makes use of a "predictive, self-learning energy management system" that allows the house to react to its environment and continuously optimize its performance. All of the building's energy usage is monitored and managed from this system, including lighting, heating, ventilation and charging of the electric vehicles. It also delivers surplus energy to the neighboring house or to the grid.
Among its functions, the energy management system learns the routines of its users to ensure that the building is adequately powered and the cars are adequately charged when required, while ensuring that usage overall is also minimized. Once all the house's occupants have left for the day, for example, its systems are put into an energy saving mode.
This internet-connected automation system also allows the building to prepare for the occupants returning home. The positions of the electric cars are monitored by GPS so that the heating can be turned on when required. It is also possible for lighting to be switched on or off and blinds to be raised or lowered.
The automation system is controlled using a mobile app, to which it connects via Wi-Fi when the user is inside the house or via mobile signal if they are away from the house. The interface of the app changes depending on the time of day and year so as to forefront the most relevant features, such as lighting controls when it gets dark. The app allows users to monitor the building's energy performance, manually control features such as lighting and indicate when they want the house to prepare for their return home or rushed departure.
In total, the house is expected to generate approximately 8,300 kWh per year and to use 4,200 kWh per year. Gizmag is told that, although no blower test has been carried out, the doors and ventilation systems meet Passive House standard.
The building also performs well in terms of its U values, a measure of heat loss when the temperature outside is at least one degree lower than inside. The walls have a U valueof 0.11 W / sq-m K and the glass façade 0.83 W / sq-m K, both of which would meet Passive House requirements. The roof would also meet Passive House standard at its best measure of 0.133 W / sq-m K, but would fall short at its worst measure of 0.235 W / sq-m K.
According to Werner Sobek, Aktivhaus B10 was planned and prefabricated within a few months, before being assembled on-site in one day. The building is completely recyclable and comprises a timber-and-textile wall construction with a full-height glazed front that uses 17 mm (0.7-in) thick vacuum glazing.
Aktivhaus B10 was completed in May 2014 and was inaugurated in July. The project will run for three years, finishing in 2017. After that, Werner Sobek says the house will either be dismantled, moved or, if the City of Stuttgart sees fit, left where it is.