Passive House Windows and Doors
The windows in a Passive House are required to have a much lower U-value than standard windows so as to prevent excessive heat loss. The recommended Passive House window U-value is no higher than 0.8W/(m²K) (sub-criteria) and an installed U-value of no higher than 0.85W/(m²K) (sub-criteria). These values are achieved by a combination of triple glazing with two low-e coatings (typically on glazing surfaces 2 & 5 and filled with argon or krypton gas), warm edge spacers and frames with increased insulation levels (sub-criteria).
Whilst this reduces heat loss through the windows, this element of the Passive House building has a dual purpose and must also allow a beneficial amount of solar gains to enter the dwelling. With this in mind the window glazing must have a minimum solar energy transmittance factor of 50% (G-factor = 0.5, sub-criteria) with 62% (G-factor 0.62) being the highest currently achievable with Passive House windows.