Phasing of the objectives The requirement will be reviewed in light of the updates of the cost optimum study and of the climate and energy targets, the most recent revision of which (June 2018) indicates that the most favorable value is above the Q-ZEN level. The 2023 review will determine whether the ZEN level can become the new standard from 2025. In any case, Wallonia is aiming for carbon neutrality in new buildings from 2027. For collective housing, the obligations are imposed on the scale of the apartment and the building. A specific report must be drawn up for the roof, facades and other common parts, based on the recommendations of the EPB certificates for the common parts. The co-ownership is responsible for implementing the recommendations for the common areas.