Temburong development, anticipated to occur soon after the completion of the Temburong Bridge linking Temburong district to Bandar Seri Begawan (BSB), offers Bruneians an opportunity to incorporate energy sustainability in developing an ecotown. These guidelines intend to assist the Ministry of Energy (MOE), Brunei Darussalam, in formulating a plan and a guide incorporating energy efficiency and conservation (EEC) measures in Temburong ecotown development. These guidelines aim to establish EEC practice requirements, minimum building energy performance, and other review and assessment requirements of the EEC section of a development plan submission. Henceforth, these are referred to as EEC building design submission as part of the overall building development plan submission to develop the Temburong ecotown. These guidelines provide guidance on best practices, methodology, and assessment regarding minimum energy performance and other EEC assessment requirements to achieve energy efficiency in commercial and public service buildings in Temburong district. These buildings are expected to become a major load demand centre for energy besides the transport sector. The Ministry of Development (MOD) approves building development applications. However, the building energy performance assessment is deemed a subset of the overall building development application. These guidelines were prepared for the responsible department in the MOE (expected to be the Sustainable Energy Department) to review and assess the design compliance according to the EEC assessment criteria provided, in addition to the existing building regulations in Brunei Darussalam. In case of any contradiction between the requirements of these guidelines and the current building regulations, the requirements of the latter shall take precedence. As these guidelines focus on EEC technical guidance, the administrative procedures and the existing statutory requirements for the building plan submission, processing, compliance, and approval are not included. This aspect of the building plan submission and processing procedures will be addressed by the ministries and authorities concerned. Successful implementation of the EEC strategies and measures recommended in these guidelines will depend on whether the existing regulatory requirements are adequate or whether specific EEC regulations will be introduced because implementation on a voluntary basis will not be effective.