Comfortably cool in summer and cozy warm in winter, all with minimum energy use: The Hohenstein Institute in Bönnigheim/Germany has expanded its current range of tests to allow modern office and living spaces, vehicle interiors, tents and even clothing to meet these requirements.
Based on EN 410 “Glass in building,” the experts at the international research and test institute determine the so-called “g-value” as a measure for the energy transmittance of materials. Manufacturers of textiles, window and multilayer glass as well as other transparent materials such as films can use the test results to optimize their products specifically with regard to low energy transmission. The energy savings resulting from a low g-value, as well as comfort aspects and consumer safety, are becoming increasingly important for marketing products.
The g-value is composed of the directly transmitted solar radiation and the secondary heat emission resulting from radiant emittance and convection on the inside of the material. A g-value of 1 corresponds to an energy transmission (heat gain) of 100 percent. Conventional uncoated glass has a g-value of approx. 0.85, which means that 85 percent of the incoming heat can be transmitted into the room behind the glazing. The rest is reflected or absorbed by the glass. Modern triple glazing has a value of approx. 0.55.
With the measurements using modern spectral photometers, tests at the Hohenstein Institute cover the wavelength range from 250 to 2500 nm (UV radiation, visible light as well as infrared heat radiation). In addition to the g-value, the tests can also provide information about direct radiation transmittance, radiation reflectance, radiation absorption factor, light transmittance and light reflectance as well as UVA and UVB transmission.