Optimization of Thermal Transmittance on Hardwood Glulam for Window Frames

The demand for energy saving products is increasing daily in numerous applications. This is especially evident in the area of building construction where the use of components with optimized thermal transmittance can contribute to energy savings. A research project was carried out to develop new wooden profiles for window production. The project focused on reducing thermal transmittance using glulam oak elements for windows frame instead of solid wood, and verifying the feasibility to use other hardwood species not previously considered. Specific experimental equipment and procedures were used to measure the thermal performance of 20 different samples of glulam elements made from oak, other hardwood timbers (okoumé, fromager, poplar, alder), different materials (cork, rubber, MDF), and with inner layers containing air pockets of different sizes. The combination of oak and alder showed the best performances. After several FEM simulations, the project team developed an adjustment of the profiles through means of FLIXO © by Infomind software to test high accuracy thermal transmittance of the samples. Samples realized by combining lamella of oak and alder were compared with actual oak profiles. Finally, the best performing sample was successfully tested according to the hot box method. For this specific purpose, a factory which took part in the project developed a window prototype. This profile is now patented as a new product, named Ottiple ® . In addition, the results show that it is possible to increase the value of hardwood species such as alder by exploiting its wood properties. The results from this project also can encourage new forms of entrepreneurship as well as the valorization of the local timber resources.