UK EPCs and New Builds

New homes in the UK receive EPCs through a process that begins before construction and ends after completion. At design stage, a SAP calculation predicts the home's performance from plans and specifications, and that prediction informs building regulation compliance and design choices. After construction, an as-built assessment, supported by evidence of what was actually built, produces the EPC that is lodged and provided to the buyer. The distinction between design prediction and as-built certificate is the most important thing a buyer can understand about a new-build EPC.

Design calculations are useful but provisional. They assume that specified materials, details and systems will be installed as designed, that thermal bridging details will be followed, and that airtightness and commissioning will achieve design values. Construction inevitably involves substitutions, site decisions and workmanship variation, and those differences are why an as-built assessment, with its own evidence, is required rather than simply issuing the design prediction as the final certificate.

As-built evidence typically includes product specifications for key items, photographs of construction stages where required, airtightness test results where testing applies, and commissioning records for heating and ventilation systems. An assessor, often a SAP assessor working with the developer's evidence, checks that evidence against the design and produces the lodged EPC. Where evidence is missing or contradicts the design, the as-built calculation should reflect the evidence, not the design intent, and a buyer who receives only a design prediction should ask for the as-built certificate.

Buyers should also understand what a new-build EPC does not cover. It is a standardised energy rating under standard occupancy and standard fuel prices, not a prediction of the buyer's bills, and it does not cover appliances, cooking or other household electricity unless the method says so. It also does not certify structural quality, workmanship generally, or compliance with every building regulation aspect; those are covered by other processes, including building control and warranties, and a good EPC does not substitute for them.

Before relying on a new-build EPC, ask for the as-built certificate and its lodged reference, and ask what changed between design and as-built calculations. Check the heating system, controls and ventilation listed against what is installed in the home, and ask for airtightness and commissioning evidence where applicable. If the developer can provide only a design prediction, treat the EPC position as incomplete until the as-built certificate is lodged.

For developers and builders, the lesson is to collect as-built evidence during construction, not after it. Photographs of insulation, details and systems are easiest to obtain while work is open, and reconstructing them afterwards is slower, less reliable and sometimes impossible. Evidence collected during construction also helps resolve queries from assessors, building control and buyers without delay.

By place, new-build EPC and building regulation routes vary by nation. England, Scotland, Wales and Northern Ireland each set their own building regulation energy requirements and EPC arrangements, with different targets, evidence expectations and timetables, and those requirements have been revised in recent years. A new-build EPC position that is correct in one nation may not be correct in another, and buyers and builders should check the nation concerned.

EU new-build rules are separate. A new home in an EU member state follows that country's EPBD implementation and building code, not UK building regulations or SAP, and its certificate is a national document under that system. Cross-border comparisons of new-build ratings should be avoided.

A common mistake for buyers is to treat a design-stage rating, quoted in marketing material, as the finished home's EPC. Marketing ratings are often design predictions, and the as-built rating can differ. Another mistake is to judge a new home solely by its EPC band, ignoring airtightness, commissioning, ventilation and overheating, which affect comfort and real performance alongside energy.

A further mistake for builders is to leave evidence gathering until completion, and then to face delays while missing photographs or specifications are sought. Evidence planning should be part of the construction programme from the start, with responsibilities assigned for each item.

Keep the design calculation, the as-built EPC, airtightness results where available, and commissioning records together as the home's energy file. That file supports future sales, retrofit decisions and warranty queries.

Questions to ask include: is this EPC design-stage or as-built, what changed between the two, and what evidence supports the as-built inputs. Those questions turn a new-build EPC into an account of the home built.