For the renovation of the École du Mail school in Geneva, which is a listed building, Zirkular is investigating on behalf of the City of Geneva how replacing windows in a building would affect its greenhouse gas emissions. The basis of this research project is the question of how sustainable the complete replacement of existing windows or their preservation with retrofitting is in the long term.
The emissions for space heating losses are considered in comparison to the construction emissions. The operating emissions consider the heat loss through the windows in the existing building and the renovation options. The construction emissions consider the manufacture and future disposal of the new layers.
There are three possible levels of intervention: replacing the window glass with vacuum glass (V1), replacing the glass with double insulating glazing with a frame doubling (V2) and, finally, completely replacing the window with new triple insulating glazing (V3).
The calculations have shown that – taking into account the decarbonisation of the heat supply – preservation with retrofitting (in this case V1) is equivalent to complete replacement.
Zoé Pahud & Achille Pidoux
