Research in focus

Controlling the weather

If only we could control the weather! While for most of us this remains pie in the sky, it’s an everyday occurrence for engineer Andreas Zegowitz and his team from the Thermal Parameters and Laboratory Climate Simulation group. They have the power to control the weather – at least, the weather in their lab at Fraunhofer IBP in Stuttgart. There they can invoke a winter chill or usher in the heat of summer, and managing relative humidity, snow, rain and sunshine is no problem at all. In their large climate chamber – one of the test setups in which they can control the weather – they have even simulated a flood. “This is where we test and do all the research for new building products for a range of construction companies,” explains Zegowitz. “We carry out all kinds of hygrothermal tests. Our customers and project partners are interested in heat flow and thermal bridges in their components, whether and where condensation occurs, how moisture gets distributed, as well as the general negative effects of climate change.” Depending on the size of what they’re asked to test, Zegowitz and his colleagues have at their disposal not only the large climate simulator, but also a three-chamber climate simulator and several other climate chambers of various sizes. “We’re set up to perform climate tests on almost anything, right up to large façade elements.”

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Most recently, the team has been working on a series of tests concerned with the drying behavior of brick walls and of flooring constructions that use screed and layers of EPS insulation. “More than a million cases of water damage caused by leaky pipes are reported each year in Germany. And damage only gets worse when there’s flooding,” explains Zegowitz. New building materials and systems can make life harder for the companies you can hire to dry out damaged areas. These days, it’s common for bricks to be filled with insulation or for buildings to be fitted with interior or exterior insulation. Then there are also non-permeable films and a lot more besides. “Building materials come in all forms and in virtually endless combinations. Choosing the right drying method calls for specialist knowledge,” says Zegowitz. The company that commissioned Fraunhofer IBP to carry out this latest series of tests has developed a new method for drying walls. One of the things Zegowitz and his team had to do is test just how effective it is. As a control, the researchers also tested two established drying methods used in the trade: sub-screed drying for the floor – once using an adsorption dryer, once not – and infrared drying for the walls.
“We built four mini test houses inside the large climate simulator and then flooded them,” explains Zegowitz. To create the flood, the researchers modified a sprinkler system so that water flowed constantly from a source at floor level, keeping the floor under five to seven centimeters of water. “To be on the safe side, we maintained this water level for two weeks,” says Zegowitz. However, full damage was achieved just three days into the test: the houses’ floors and especially their walls were completely saturated. Zegowitz explains the problem: “Since walls absorb water and are reluctant to release it again, it’s all the more important to have effective drying methods.”
In three of the four test houses, the researchers tested drying methods in a variety of combinations; the fourth house served as a control. “A certain amount of moisture remains behind in any building so we had to eliminate this from the data we collected from our test houses,” explains Zegowitz. “This was the only way to accurately calculate how effective the different drying methods are.” In this series of tests, the researchers examined the effectiveness of various methods: drying the sub-screed using an adsorption dryer; using a sealed drying system in which air is piped in; and by allowing it to dry naturally. Similarly, drying of the walls was attempted in three ways: by natural means, by using infrared heating panels, and by applying the newly developed drying method. “Nearly all of the drying methods we tested proved to be reliable overall. We did observe that heat from the infrared panels did not fully penetrate the 36-centimeter brickwork with thermal insulation,” Zegowitz continues. “This is where the new drying method proved to be effective.”
By now the large climate simulator has been dried out again, the test houses have been dismantled and the next set of tests can begin. Zegowitz and his team have carried out many exciting tests over the years, such as determining thermal transference in sections of rail vehicles or using a climate-controlled wind tunnel to simulate conditions that cause aircraft parts to ice up. They also explored the reliability and durability of shading systems integrated between panes of window glass, under conditions such as wind and vacuum pressure, fluctuations in temperature and humidity, and artificial sunlight. The researchers have also performed tests to determine the likelihood of high-voltage cables icing up, which involved creating artificial snow. Besides the more common climate-based tests on new façade components, the researchers also regularly carry out tests that are more exotic. “A whirlpool bath manufacturer had us test whether their product could perform perfectly outside at temperatures of minus 20 to minus 30 degrees Celsius. There’s a whole lot of electronics in these things that have to work at such temperatures,” says Zegowitz. He then smiles and adds, “Of course, we didn’t explore what else you might do with a whirlpool bath – that’s unfortunately not in our job description.”
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