A team of Steinbeis experts are working on the development of a method for selecting sun protection solutions
There is increasing public awareness of issues relating to sustainable products and systems, which should not only fulfill their intended purpose but also save resources and energy – and be easy and efficient to re-use. Such requirements also affect projects relating to buildings. The German Sustainable Building Council (DGNB) has developed a sustainability concept for assessing and certifying such projects. It looks at six key areas: ecological, economic, sociocultural, and functional factors, technology, and process and site quality. The idea is to assess and select the large number of materials that are now used in buildings. The Saxon Textile Research Institute (STFI), a research faculty at TU Chemnitz, joined forces with the Chemnitz-based Steinbeis Transfer Center for Drive and Handling Technology in Mechanical Engineering to look into different ways to bring an array of sun protection measures applied to buildings into harmony with sustainability criteria and functional requirements.
Glass areas offering indoor or outdoor protection from the sun function as an overall system. Sunshade elements make it possible to regulate temperatures and keep rooms comfortable and as such, they constitute part of the overall building design, not only because they reduce the impact of heat in the summer but also because they save energy and provide climate control. Fabric sun protection at the workplace also makes it possible to meet requirements laid down under DIN standard EN ISO 9241-6, which dictates workplace lighting. By optimizing lighting conditions, sun protection can even help raise productivity at the workplace. It also makes it possible to minimize lighting energy requirements by optimizing the use of natural daylight.
As part of a research project sponsored by the Federal Ministry for Economic Affairs and Energy (project ref. MF150060), the Saxon Textile Research Institute (STFI) and the Steinbeis Transfer Center for Drive and Handling Technology in Mechanical Engineering have developed a method for selecting sun protection fabrics in keeping with key parameters affecting construction projects so that these fabrics can be included in sustainability assessments. In addition to sustainability issues relating to the actual technology or environment, one factor that plays an essential role with fabric sunshades is durability because it affects sustainability with respect to the life cycle cost of a building.
STRESS IMPOSED ON SUNSHADE MATERIALS
Previous testing had already looked in detail at the durability of sunshades used in buildings compared to testing carried out on a laboratory scale. A variety of stresses come together in use, and these have an impact on materials: radiation (from sunshine), changes in temperature, humidity, and mechanical stress. Accordingly, a cyclical stress procedure was designed for laboratory testing in order to replicate realistic operating conditions for the kinds of fabric sunshades that are used indoors, including pleated blinds, roller blinds, curtains, and vertical lamella blinds.
TESTING UNITS FOR FABRIC MATERIALS
To run its complex testing procedures, the Steinbeis Transfer Center designed and constructed its own technical equipment. The stress testing units that were developed consist of a thermally insulated test chamber with a window on top. The fabrics undergoing testing (measuring 600 x 600 mm²) are moved pneumatically inside the testing unit. This is to simulate the opening and closing of blinds in use. Temperature and humidity cycles are also regulated inside the test chamber. An “artificial sun” has been mounted above the window to subject samples to the kind of radiation emitted by the sun. Depending on requirements and the durability of material samples, testing normally lasts three to seven days. Each complete testing cycle corresponds to roughly two years of actual use.
The Steinbeis Transfer Center for Drive and Handling Technology in Mechanical Engineering also designed and constructed a further unit specifically for testing larger sun protection equipment measuring up to one meter in width and two meters in length. These units work in a similar way to the stress test units. Materials are subjected to stress in four time-controlled testing chambers with varying temperatures, relative humidity levels, synthetic sunshine, and mechanical movements (opening and closing of windows).
As well as examining samples on the day of testing, the project team also looks at samples before and after each testing procedure. Visual criteria are assessed – such as waviness, structural changes to surfaces, loose adhesives, or cracks – and findings are logged and placed into categories. This categorization process also includes changes in dimensions and material mass. The criteria for the different categories were defined by the project team with a working group at the Industrial Association for Interior Privacy Screens and Sun Protection.
ONGOING DEVELOPMENTS IN THE RESEARCH PROJECT
Although the fundamental project requirements have already been fulfilled, the project is by no means over. Only recently, the project team extended its testing facilities so that they can simulate the stresses sun protection materials are exposed to when they are used outdoors. Its units are therefore capable of replicating bending strain resulting from sunlight, rain, or temperatures just above freezing.
The testing procedures and devices have now been certified and are already in active use for industrial projects at the Saxon Textile Research Institute’s testing facility. To include sun protection fabrics in sustainability assessments of planned developments, irrespective of whether a project relates to new or renovated buildings, the experts have also developed a mathematical model for their research project. This gives planners, architects, and providers of building equipment a decision-making instrument for selecting sun protection materials that match the individual requirements of a building and its intended use. It also validates the parameters of sun protection materials (such as visual, thermal, and acoustic variables, as well as durability) with weighting factors, and these are then categorized according to different correlations and mapping algorithms (development phase, learning phase).
Once the system is actually in use, materials are only offered to planners and designers if they meet defined requirements. This approach was chosen so that other application scenarios or other groups of materials (such as flooring materials) could be looked at.
The project team has confirmed that the solution can be applied to business practice. A sun protection unit that features fabric has been included in an evaluation of sustainability factors for renovations being carried out to school buildings. Due to a conservation order on the facade, it was only permitted to mount sun protection units on the inside of the building.