The government has published a circular letter that sets out that all new buildings should be almost zero-energy buildings from 31 December 2020 with respect to regulation 25B of the Building Regulations 2010.
The guidance in the circular letter applies to buildings and building work in England and excludes buildings owned and occupied by public authorities.
Regulation 25B states: "Where a building is erected, it must be a nearly zero-energy building."
For new buildings owned and occupied by public authorities, the coming-into-force date for regulation 25B was 1 January 2019.
Regulation 25B also states that meeting the Target Emission Rate required under regulation 26 involves "undertaking an analysis of the technical, environmental and economic feasibility of using high-efficiency alternative systems, which include decentralised energy supply systems based on energy from renewable sources and taking this analysis into account as required by Regulation 25A".
The government also says that "the energy efficiency standards of the building regulations are currently under review".