The renovation rate in the building sector is still too low to achieve the energy turnaround within the timeframe envisaged by the German government. One step in this direction may be a greater degree of prefabrication of the components. Researchers from Fraunhofer IBP and Fraunhofer IEE are developing a façade module that integrates technical building equipment (TGA) and supplies it with renewable energy to heat, cool and ventilate the rooms behind it. This is made possible by a PV system integrated into the module facade for energy generation, a micro heat pump for heating and cooling, and a decentralized ventilation unit with heat recovery.
Buildings account for a significant share of total energy demand and greenhouse gas emissions in Germany. Energy-optimized buildings, intelligent control and networking, and an economical and climate-friendly energy supply for homes are therefore central components of a successful energy and heat transition. Photovoltaics (PV) will play a significant role in a sustainable energy future — for example, in the renovation of existing facades, but also when it comes to reducing the energy demand and consumption of new buildings.
Research teams at Fraunhofer IBP and Fraunhofer IEE are currently developing a so-called EE-module façade (renewable energy module façade), which supplies the building with environmentally friendly electricity and thus heats, cools and ventilates the rooms. At the heart of the module is a PV system combined with a heat pump as a highly efficient heat and cold generator, as well as a decentralized ventilation unit with heat recovery. All the necessary technical components are accommodated in the EE module façade element, thus achieving a high degree of prefabrication. The German Federal Ministry for Economic Affairs and Energy BMWi is funding the joint research project. The project partners are Implenia Fassadentechnik GmbH as the designer of the EE modular façade. The company Lare GmbH Luft- und Kältetechnik develops the heat pump, and LTG AG complements the area of decentralized ventilation.
Minimally invasive facade renovation
The aim of the research project is to develop a cost-effective modular renovation and new construction façade, whereby the renovation is to be minimally invasive — as is the case with many operations in medicine. “We are not renovating the entire building, just the facade. In the future, the old facade will be replaced by new industrially prefabricated modules with integrated plant technology, which will thus make it multifunctional and adapt it to the new energy standards,” explains project manager and scientist at Fraunhofer IEE Jan Kaiser. “The entire heating/cooling and ventilation technology for the office space behind it will be integrated into the facade.”
Since the modules can be prefabricated, they can be produced off the shelf. This gives planners and investors a high degree of cost certainty and a clearly defined cost framework. The replacement takes place in just a few hours. Since the heating and ventilation technology is already integrated, no new pipes need to be laid inside the building. The facade only needs to have a power connection to be able to air condition and ventilate the rooms even in times without PV power. The installation and coordination effort at the construction site is reduced. Ideally, the users of the rooms do not have to move out separately during the refurbishment.
The EE modular façade is particularly suitable for office, administrative buildings and schools built in skeleton construction — a construction method that was common in the 50s, 60s and 70s. Instead of load-bearing walls, reinforced concrete columns hold the floor slabs. During the renovation, the old façade elements are removed and the new type of floor-to-ceiling modules are hung in front of the building structure. A single technical unit of the EE module facade is 1.25 m wide and 30 cm deep. Each unit can supply a room of approx. 24 m².
Modular façade as an energy envelope
The built-in PV system generates the energy and supplies power to the system components such as the heat pump. This functions as a heat and cold generator at the same time. It is the defining component of the technical unit of the EE module façade and is characterized by intelligent control of the energy flows. From one unit of electricity, it can produce three to four units of heat. Via a fan coil unit mounted in the air gap behind the PV element, it extracts the heat from the outside air and emits it as heating heat to the (office) room behind it, also via a fan coil unit. If it needs to cool instead of heat, the cycle is reversed, extracting heat from the indoor air and dissipating it to the outdoor air.
An integrated decentralized ventilation technology unit controls the air exchange and heat recovery. By selectively interconnecting air dampers, only one fan is required, which minimizes power consumption. The system developed by Fa. LTG, the ventilation unit alternates cyclically between supply and extract air operation and thus performs a kind of breathing. In addition, vacuum insulation elements provide thermal protection.
“The new EE modular façade offers precisely coordinated thermal and solar protection while at the same time keeping energy requirements low and providing a high level of user comfort,” emphasizes Michael Eberl, a scientist at Fraunhofer IBP and a colleague of Jan Kaiser in the project. About 25 to 30 percent of all office buildings were built in skeleton construction from 1950 to about 1990. They have a consumption of 3200 gigawatt hours (GWh) per year. “With our RE module façade, consumption can be reduced to 600 GWh. The low renovation rate of one percent per year could also be increased by the high degree of prefabrication,” says Kaiser.
Tests in the experimental facility for energy and indoor climate studies (VERU) of Fraunhofer IBP in Holzkirchen
Currently, the project partners are testing the demonstrator of the EE module façade on the south front of the VERU building, including a test room behind it. Both the demonstrator and the test room are equipped with extensive measurement technology. In addition, time-dependent controlled internal heat and humidity sources — which simulate “users” in the rooms — are installed to demonstrate the functionality in a real office environment. Among other things, parameters such as air temperature, air humidity and air velocity at different heights as well as the illuminance are determined — parameters that are relevant for the comfort in the room. The electrical consumption of the individual components of the technical unit of the EE module façade is recorded, as are the yields of the PV element, in order to calculate an energy balance. The interaction of all components already works very well, individual components are currently still being optimized.