The 2022 version of the Building Regulations now applies not only to new buildings but also to existing properties. This is particularly important for renovations, extensions, or retrofitting existing dwellings. 

For instance, when a wet heating system is newly installed or fully replaced in an existing building, it must be designed to meet the heating needs of the dwelling at a maximum flow temperature of 55°C or lower. 

If this is not possible, the system should be designed to the lowest possible temperature that still meets the heating needs of the dwelling. To facilitate this change, the new Regulations now require a full room-by-room heat loss calculation to be carried out before replacing the boiler to ensure the correct sizing of replacement heating systems. 
This change will affect installers of all heating system types, including oil, gas, and renewable systems. It is also important to calculate the output of the existing heat emitters to offer advice on energy-saving measures that could be introduced when changing the boiler. 

From 15th June 2022, all oil heating installations will need a room-by-room heat loss calculation as part of the initial site survey. 

Section 5.8 of the new Regulation states that “The specification of space heating systems should be based on both of the following:

• An appropriate heat loss calculation for the dwelling. 
• A sizing methodology that takes account of the properties of the dwelling, such as the Chartered Institute of Plumbing and Heating Engineering’s Plumbing Engineering Services Design Guide."

This means that a room-by-room calculation is now required, and a 

whole-house-type calculation is no longer allowed.