Handbook This non-mandatory Handbook provides details of the energy efficiency requirements of NCC Volume One. It aims to provide practitioners with sufficient knowledge to successfully apply energy efficiency requirements for commercial buildings. The Handbook has a practical focus, and is intended to provide an understanding of the policy objectives and the technical basis of the NCC requirements. This will enable practitioners to manage a range of situations where different design and assessment tools are needed. This document provides guidance on the NCC 2019 Volume One energy efficiency requirements.