RE2020 (in force since 2022) imposes energy (Bbio, Cep, Cep,nr) and carbon (Ic) calculations based on regulatory thermal simulation; to verify that the delivered performance matches design intent, IPMVP Option D (calibrated simulation) is the reference tool.

The regulatory thermal study (formerly RT2012, now RE2020) predicts theoretical consumption, but the delivered real performance often differs because of construction practices and occupant behaviour. IPMVP Option D builds a calibrated model on first real-life measurements and compares it to the RE2020 forecast, providing contractual conformity through commissioning and post-occupancy evaluation. This is an emerging market for CMVPs specialised in new construction.

Define the calibration tolerance in the design contract — without it, 'delivered performance' becomes a renegotiation rather than a verification.