Designers and contractors must make new buildings more energy efficient under proposed changes to the Building Regulations announced on Wednesday.

The amendments to Part L aim to reduce energy consumption 25%. They are part of the government’s drive to tackle climate change.

One of the key revisions is for housebuilders to prove dwellings are airtight by pressure-testing them prior to handover.

The proposals set the energy standard for a whole building, rather than for individual elements, leaving it to the contractor to decide how to comply. Contractors could, for instance, trade off the insulation level in the building's fabric against the efficiency of the boiler installed.

Proposed changes to the ventilation regulations, Part F, were also announced on Wednesday. These were introduced to ensure stale air is replaced at an adequate rate after the requirement in the energy regulations that the building fabric is more airtight. The changes come into force next year.

Consultation papers are available online at