Approved document L2 of the Building Regulations places requirements for energy conservation upon commercial buildings.
This is split into two distinct primary documents:
These statutory documents give top level detail on English Government requirements, a further second tier document, the Non-Domestic Building Services Compliance Guide, gives detailed guidance for services including specific efficiency requirements for space and water heating. Devolved administrations in Scotland, Wales and Northern Ireland have region specific documents and, in some cases, differing requirements.
In order to demonstrate compliance for new buildings an emissions compliance calculation must be carried out, typically using SBEM (Simplified Building Energy Model) or DSM (Dynamic Simulation Modelling). Given the relatively challenging overall building compliance targets set in the current 2016 iteration of Part L the efficiency of heating and hot water equipment is a key specification point which can have a marked impact on the overall DER.
In the case of retrofit and replacement projects, compliance is simpler; however, boiler and water heater efficiency has a part to play here as Energy Performance Certificates (EPCs) for buildings can be improved by using more efficient products.
By using Andrews Size-it to determine the appropriate specification of water heater for a given project, it is possible to claim an additional 2% efficiency credit within the compliance calculation, section 8.6 of the Non-Domestic Building Services Compliance Guide gives more detail.
You can find out more about Part L of the building regulations here
