Multitasking for the building industry with smart façades

Research in focus June 2013

We all know how practical it is to be able to multitask; it is something most of us benefit from on an almost daily basis at work and at home. But humans aren’t the only ones capable of getting several things done at once. This is the basic idea behind much of the thinking of research scientists at the Fraunhofer Institute for Building Physics IBP. One of the fundamental questions they are addressing is how to make buildings and their individual components more versatile, and how to get them to perform specific tasks. Façades, for instance, are more than simple covers providing protection from the elements – they are supposed to perform other functions, such as helping to improve the indoor climate, to increase the building’s energy efficiency and to prevent the growth of unwanted organisms on exterior walls. That’s why several Fraunhofer IBP departments all share the common objective of finding innovative solutions for smart façades.

In the Energy Efficiency and Indoor Climate department, Herbert Sinnesbichler and his Evaluation and Demonstration group are working on new developments in this field: “A building’s envelope is its interface with the outside world, meaning it determines the energy performance of the building as well as the level of comfort in the individual interior spaces. That’s why our work focuses in equal measure on evaluating the energy efficiency of building envelopes, offering consultation during the planning phase, and developing new and innovative façades and roof constructions together with industrial partners.”

The importance of taking into consideration a façade’s functionality – or rather, the functionality of the materials it is made of – before beginning a construction project is shown by the regrettable frequency with which buildings require retrofitting. It’s usually not enough simply to erect a façade that looks good. The comfort of the building’s inhabitants and the building’s energy efficiency play a much more important role. But instead of learning this the hard way, by having to carry out retrofits or avoidable repairs, it is better to use dynamic building simulations and mock-ups (replicas). That is why, in work on a planned new company headquarters for example, Sinnesbichler and his team used a technical mock-up at Fraunhofer IBP’s VERU modular test facility for energy and indoor environments to measure and study the façade structure’s influence on the building in terms of energy, lighting and comfort. The reason for this was that the building was to be given a relatively new kind of hermetically sealed double-glazed façade. “When you’re building a new structure, such as a large office block, there’s a certain degree of risk if you rely solely on the drawing board and simulations,” explains the engineer. “A mock-up allows us to test a number of things, including the building’s functional capabilities. We’re able to predict what the indoor climate will be, and we’re able to use the measurements we obtain to optimize supplementary simulation models.”
Fraunhofer IBP scientists are also conducting large-scale trials under real conditions to test innovative uses of materials. Most of us have encountered phase change materials (PCMs) in the form of cool packs or heat pads. But PCMs can also be integrated into façades to store heat or cold. They warm up during the day by drawing heat from their surroundings, heat that they then release during the night as they cool down. According to Sinnesbichler, this technology has numerous advantages: “When combined with a decentralized ventilation system, PCMs can be used to cool the airflow entering the building,” he explains. This means that buildings with decentralized ventilation systems become more energy efficient. Fraunhofer IBP researchers have successfully implemented and investigated the interplay between PCMs and ventilation systems at the Fraunhofer inHaus Center for the research of residential and commercial properties in Duisburg, Germany. “There are all sorts of different phase change materials available that can be used in many different ways, for lots of different applications – not just in construction,” explains Sinnesbichler. One idea this led to was the PCM cup, a vessel that ensures beverages are always at the ideal, i.e. drinkable, temperature.
Herbert Sinnesbichler is keen to develop the potential of façades for generating, storing and effectively utilizing energy in future. “Unfortunately, people are currently very focused on photovoltaics, but there is so much more that is technically feasible,” he says. One further possibility is using façades to cool buildings by passing water through integrated photovoltaic elements. To date this system has only been used to generate electricity, however it would be just as possible to use it to cool the concrete core of a building. Sinnesbichler is convinced that “incorporating more technology into a building’s façade and thus implementing more building physics is always a good idea,” but that, unfortunately, it usually proves almost impossible to see such ideas through in practice due to the number of different industrial partners and trades involved in a construction project. “We’re currently working together with partners in industry on a solution to this problem. If all the necessary technologies were already incorporated into prefabricated façade components before they arrived on site, there would be no need for time-consuming and costly coordination between different specialist companies working on the job,” Sinnesbichler explains.
In many respects, the range of possibilities offered by smart façades is not even close to being exhausted. The façade technology experts are working with colleagues from the Biology department to examine ways of producing biomass on the façades of buildings. After all, there is no reason why the principle that works so well in specialist algae farms can’t also be extended to function on the vertical shells of buildings. 
Figuratively speaking, the investigative work being carried out by Dr. Christian Scherer and his team also revolves around biomass on façades. However, the  Ecology and Microbiology Group’s work is all about preventing the undesirable growth of organisms such as algae and fungi on building envelopes – which is why they regularly test the effectiveness of façade coatings on behalf of manufacturers, for instance. The research scientists carry out endurance tests at regular intervals on small individual test pieces as well as on the Zwillingshäusern (twin houses) at the Fraunhofer IBP’s outdoor testing facility in Holzkirchen. These tests serve less to examine the overall effectiveness of biocides, and more to ascertain the degree to which they are leached out of façade coatings (only German). Manufacturers are constantly working to improve existing products. “Our studies have shown that rain leaches encapsulated active substances out less quickly than non-capsulated ones,” says Scherer. “Using this type of façade coating not only means that fewer active biocide components enter the environment, it also means that the building’s façade lasts longer, i.e. has to be renovated less frequently.”
Scherer and his team use these same criteria to investigate numerous other components used in façades, such as plaster and masonry mortar. Their objective is to develop processes based on existing or proposed standards that bring together results from studies conducted outdoors with laboratory test findings. “The evaluation model derived from this will make it possible to reliably forecast environmental impacts,” Scherer says.
“Façades will perform more and more functions in future,” predicts Herbert Sinnesbichler, “including in the field of telecommunications.” Integrated sensors will be able to recognize when inhabitants are close to home, and, depending on the technology built into the building, send a signal to control the lights, windows, central heating, etc. The sky’s the limit as far as multitasking is concerned.

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