It is well-known that our building stock is outdated and that it is responsible for an important share of greenhouse gas emissions. Europe has the ambition to reach a CO2 neutral economy by 2050. To achieve these ambitions we need strategies to reduce the CO2 impact of the building stock. The transition to a CO2 neutral building stock is associated with an enormous amount of building materials necessary for renovations and new buildings. Therefore there is need to

• balance between energy performance of buildings (operational energy) and material use (embedded energy),
• investigate what measures or combinations are in favor, both in terms of the building envelope and HVAC systems,
• search for the tipping point between demolition + new built instead of deep renovation,

and these questions should be researched for a variety of building typologies (e.g. row house, detached house, apartment building, office building) with a varying inherent quality (e.g. degree of insulation, existing HVAC systems).

Often decisions are based on one parameter (typically energy use or cost) which leads to suboptimal scenario’s because the CO2 impact of building materials is neglected. In addition a shift can be observed towards a larger impact of the materials for buildings with a high energy performance, due to the reduced energy demand.

Therefore a multi-criteria approach will be developed that allows to assess renovation strategies based on environmental impact and CO2 emissions (LCA), actual energy consumption and life cycle cost (LCC), without compromising thermal comfort and circularity. This must allow for the development of robust optimal strategies to upgrade the building stock, that can act as a support for shaping the future renovation policy.