Unlike countless schoolchildren and students around the world, tests do not fill the scientists at the Fraunhofer Institute for Building Physics IBP with dread. On the contrary, they enjoy putting products and services to the test. The researchers carry out complex building physics studies at Fraunhofer IBP’s efficient and well-equipped laboratories and test centers and at its outdoor testing site in Holzkirchen, which to the best of our knowledge is the worldwide largest facility of its kind. Modern laboratory measuring techniques and computational methods help them develop and optimize building products for practical applications. They also carry out experiments in environmental test chambers, simulation facilities and existing buildings to assess components and overall systems for new buildings and renovation projects based on the principles of building physics. In addition, Fraunhofer IBP has been approved by the German building inspection authorities as a testing, monitoring and certification center for building materials and building techniques in Germany and the rest of Europe. Four of the institute's test laboratories have been granted flexible accreditation by the German accreditation body Deutsche Akkreditierungsstelle GmbH (DAkkS) in accordance with DIN EN ISO/IEC 17025. This entitles them to develop new test methods and to modify existing methods. One of these accredited labs is the so-called spectroscopy laboratory headed by Almuth Schade.
“This is where we determine the radiometric and photometric properties of building products, in other words spectral quantities such as transmittance, reflectance and absorption as well as the total energy transmittance and color rendering of product specimens,” explains the
Energy Systems department scientist. Measurements are conducted both in the short-wave solar radiation range (visible light) between 300 nm and 2,500 nm and in the long-wave thermal radiation range between 2,500 nm and approx. 50,000 nm. “Nowadays, a high proportion of energy consumption is used for heating, cooling and lighting buildings,” says Schade. Accordingly, energy savings in these areas are particularly effective. “Optimal use of daylight and effective thermal insulation in winter and summer can significantly reduce energy needs. For this purpose, high-efficiency glazing along with technologies such as electric blinds provide protection from the sun. These are the kinds of products that we test. After all, only if you know their characteristics will you be able to get the most from them.” And so manufacturers send Almuth Schade all kinds of glass, membranes and screens along with a huge assortment of solar protection materials, paints and varnishes for her to test in accordance with all relevant national and international norms and standards.
Taking pride of place in her laboratory are two measuring instruments that look pretty nondescript from the outside. To the untrained eye, the highly sensitive apparatuses look like two metal boxes and not much more. The high-power double-beam spectrometer, or UV/Vis/NIR spectrometer, measures radiation in the short-wave range. To this end, handy-sized specimens (5 cm x 5 cm) are placed in front of the
integrating sphere (also known as an Ulbricht sphere)
, through which they can be irradiated, wavelength by wavelength. . “What interests our customers is how much light a particular specimen lets through, what is reflected, and how much energy gets through in total,” says Schade. However, the spectrometer also allows the scientist to test and evaluate the color rendering of objects such as glass and glazing products. “This information is useful for museums, for example. To create optimal lighting conditions for artworks, for example, the glass used to protect them must not let through too much blue or too much red light.”
For measuring long-wave (thermal) radiation, Schade uses an FTIR spectrometer. Again, specimens of various building products – from glass to roofing membrane – are placed in front of the spectrometer and exposed to long-wave radiation.
Often people want to find out how strongly surfaces heat up. “Not too long ago, a boat builder approached us about testing the paint for the deck of one of his boats. His customer wanted to make sure that his feet – and those of his guests – didn‘t get scorched when out on the deck even on very sunny days,” says Schade, illustrating the diverse reasons people come to her for measurements.
Products and services have to comply with a huge variety of norms and standards – and not just in Germany either. Accordingly, knowing the ins and outs of building product regulations is critical for Schade: “As an accredited test laboratory, it is particularly important for my colleagues and me to keep abreast of any changes.” For some materials, however, there are no norms (yet), explains Schade. “In such cases, we base our measurements on existing ones – ultimately, our customers should end up with usable data, norms or no norms.” In recent times, German norms have had to share the spotlight with international and supplementary national standards, many of which emanate from the U.S. and the U.K. For example,
are of particular interest in terms of certifying sustainability and building quality. German manufacturers also want their products to meet these standards. Fraunhofer IBP is happy to oblige by additionally testing products and services according to these criteria.
The characteristics that Almuth Schade measures in the spectroscopy laboratory for a great variety of building products also flow into the
developed by Fraunhofer IBP. Planners and architects use the programs in this software family to calculate the coupled heat and moisture transport in components.
“And when it’s difficult to test a component in the lab, we also have the means at Fraunhofer IBP to carry out in-situ testing,” says Schade. This means that the tests are moved to somewhere with real-life conditions. “For example, the characteristics of slats can’t be calculated all that easily using the spectrometer. This is where the calorimetric façade and roof testing equipment at Fraunhofer IBP’s outdoor testing site in Holzkirchen is used to complement the lab measurements.” (ate)