Dynamic Insulation System applied to Window Frames (Part 1) - Evaluation of the thermal insulation efficiency of the proposed window frames

In order to insulate buildings more efficiently, many insulation methods have been proposed and successfully applied to the building envelope, including areas such as walls and windows. However, it is also important to insulate window frames efficiently because they usually contribute the greatest heat loss. The authors propose a new dynamic insulation system for window frames, with an active ventilation function and a heat pump for heat recovery. This system is composed of three parts: window frames that use a porous material for dynamic insulation, a mechanical ventilation system, and a heat-recovery heat pump system. This paper describes a computational simulation study of the technical feasibility and the thermal insulation efficiency of the porous material in the proposed system. First, a window frame was designed containing a porous material such as a packed bed of particles (i.e. glass wool, mineral wool, aluminum particles, etc.). Then, to verify its thermal insulation efficiency, the temperature contribution of the window frame was evaluated using computer fluid dynamics with different coupled conditions, such as the indoor/outdoor pressure difference. In addition, to verify the effect of moisture condensation, the relative humidity in the porous material was calculated based on conditions such as the outdoor air temperature, humidity ratio, indoor/outdoor pressure difference, and porosity of the insulation material. The calculated results show the thermal load was inversely proportional to the indoor/outdoor pressure difference. Moisture condensation in the insulation material depends on the outdoor temperature, humidity ratio, and porosity.