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Outline ACDs Acceptable Construction Details



This guide to Acceptable Construction Details (ACDs) is intended to help the construction industry achieve the performance standards in the Technical Guidance Document (TGD) to Part L of the Building Regulations 2011- Conservation of Fuel and Energy - Dwellings.

This Guide

This guide focuses on issues concerning thermal bridging and airtightness. The guide is presented in two sections.

Section 1 discusses the general theory of insulation continuity and airtightness in construction. A common approach to the design, construction and testing methodology is considered and suggestions are made for the general improvement of the process.

The use of the Acceptable Construction Details in the context of Technical Guidance Document L is discussed. A checklist identifies the essential information to be considered during design and construction, the layout and use of the ACDs sheets are explained.

Construction detailing can create opportunities for increased design flexibility and overall energy efficiency. The increasing significance of detailing and the principles of enhanced detail performance are discussed and illustrated using an example design specification.

Finally, an overview of "How to achieve good performance in thermal bridging and air infiltration" is presented.

Section 2 of this guide is in seven parts on separate web pages. Section 2 provides large scale indicative detail drawings of thermal insulation and airtightness provisions for specific construction interfaces.

The co-operation of the UK authorities (Department of Communities and Local Government) is gratefully acknowledged in enabling the adaptation of the details in its publication “Limiting thermal bridging and air leakage” for official use in Ireland. The details have been modified and extended to reflect construction practice in Ireland, and have been updated to reflect the current requirements in Building Regulations. The details are accompanied by comments and checklists to assist the Designer and Builder achieve the guidance provided in Technical Guidance Document (TGD) L 2011 Conservation of Fuel and Energy in Dwellings of Part L of the Building Regulations at various stages throughout construction. These checklists will also be of assistance to Building Control Authorities.

Application of Acceptable Construction Details

The guide and the ACDs have mainly been conceived in relation to the construction, alteration and extension of dwellings. They are also valid in non-domestic buildings of similar construction.

Use of the ACDs during construction will enable the builder to demonstrate that provision has been made to eliminate all reasonably avoidable thermal bridges in the insulation layers (so far as the details apply). Further specific guidance is also to be found in the Technical Guidance Documents.


The Department would like to thank all those involved in the development of these Acceptable Construction Details.

The Department of the Environment, Community and Local Government would like to acknowledge the following for the use of photographs in this document:


Viking House


Irish Agrément Board