Passive house windows

In order to achieve passive house certification, windows must not exceed a U_W value of 0.8. Since the introduction of the Energy Saving Ordinance (EnEV), the U-value (heat transfer coefficient) has replaced the k-value to provide a uniform, Europe-wide designation. This value describes how much energy or heat per m² of window area can escape from the inside of the building to the outside. A passive house window has no specifications in regards to materials. It makes no difference whether the windows are made of wood, plastic or aluminium. In principle, any material can be processed into a passive house window as long as it meets the U-value requirements. Passive house windows are certified by the Dr Wolfgang Feist Passive House Institute. According to this institute's standards, the entire window, including the glass and frame, must not exceed a U-value of 0.8. The window should have a g-value of ca 50%. The U_W value represents the thermal transmittance of the frame (U_f) and the glass (U_g).

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The U-value (heat transfer coefficient) describes the efficiency of a window in terms of thermal insulation and heat transfer. Since the introduction of the German Energy Efficiency Directive (Energieeinspar-Verordnung, EnEV), this has replaced the k-value. This allows the measured values to be compared across Europe. The U-value indicates how much energy per m² of window area can escape from the inside to the outside. A lower heat transfer coefficient means that less heat can escape through the window, representing a higher level of energy efficiency. The thermal transmittance of the entire window (U_W) is divided into a U_f and a U_g value, where the Uf value reflects the thermal transmittance of the window frame and the Ug value reflects the value of the glazing

• U_w(w = window): Heat transfer coefficient of the entire window
• U_f(f = frame): Heat transfer coefficient of the window frame
• U_g(g = glazing): Heat transfer coefficient of the glazing

The g-value (solar energy transmittance factor) describes the total energy permeability of a transparent component such as window glass. The g-value consists of two components: the proportion of solar radiation that passes through the window and the heat emitted by the glass to the interior by solar radiation. A g-value of 1 represents a heat gain or an energy transmission of 100%, which represents a complete conversion of the incident solar energy. Windows normally achieve a g-value of 0.85. This means that 85% of solar energy can be converted directly into heat. A more energy-efficient triple glazing achieves a g-value of 0.55. This means that the interior is not heated as quickly by the solar energy. This is particularly advantageous in the summer, as the interior of the building stays cool longer.

Professional installation of your passive house windows ensures that they can achieve the highest possible energy efficiency. heroal has more than 3,500 installation professionals throughout Germany. They will help you to select your passive house windows, deliver them quickly and conveniently and provide professional installation. On request, our specialist partners can also remove your old windows. Use the heroal partner search tool to find a partner near you in just a few quick steps.

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Passive house windows are suitable for both existing houses and new construction projects. Even if you are not trying to achieve passive house certification, installing windows that meet the passive house standard improves the energy balance of your house and reduces heating costs. Thermal images clearly show that inadequately insulated windows are the primary source of energy loss. Binding minimum energy efficiency standards for windows were not defined until 1995. As a result, windows installed before 1995 generally have a significantly lower energy efficiency standard than modern windows.