Original Article

Accelerating decarbonisation of housing through deep energy retrofit using modular circular solutions − energy performance impacts & post occupancy evaluation

A case study into deep energy retrofit of social housing in Ireland utilising modular circular solutions, covering design and realisation with a focus on energy performance impacts and occupant feedback

School of Architecture and Built Environment, Technical University of Dublin, Ireland

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Received: 12 April 2025
Accepted: 26 November 2025

Abstract

The European Union has introduced a range of policy and legislative measures to drive decarbonisation and support the transition to a circular built environment, including a strategy for widespread building and housing energy renovation. Modular construction has been highlighted as a potential pathway to accelerate these objectives. However, significant challenges remain in applying such approaches within a highly complex and heterogeneous building stock. This novel research examines the application of modular solutions in retrofit via a case study of a deep energy retrofit of two 1970's social houses, including application of innovative modular systems, providing an overview of design development, prototyping and realisation, focusing on modularity, circularity, and thermal / energy performance, including occupant feedback. Using a grounded case study methodology integrating mixed qualitative– quantitative methods, the study provides detailed insights into the applicability, challenges and benefits of modular circular retrofit solutions, and resulting thermal and energy performance impacts and occupant feedback. The findings address key knowledge gaps around modularity and circularity in retrofit contexts, showing that conventional modular systems can be adapted to serve as over-clad retrofit solutions while integrating design-for-disassembly and advanced circularity principles, achieving advanced thermal upgrade with associated energy efficiency improvements, and positive occupant experience and benefits.