Improvements to design and construction methodology require appropriate performance benchmarks to ensure the right targets are set and achieved. The increasing occurrence of heatwaves will cause many properties to overheat, with single-aspect properties in urban areas at greatest risk. Passivhaus and EnerPHit provide a good indication of overheating risk and how to reduce this. The ultra-low-energy consumption offered by EnerPHit could also complement heating from low-carbon electric sources, ideally via high-efficiency heat pumps connected to a central heating system, perhaps augmented by solar hot water panels. The cost of maintaining or upgrading an existing district heating system should be financially justified in relation to the long-term cost of EnerPHit. The significantly improved airtightness coupled with the use of Passivhaus-certified components reduces the risk of unintended air leakage. Finally, the use of an efficient mechanical ventilation with heat recovery unit ensures there is always sufficient ventilation which can be boosted as required by the building occupant.