Toward optimal retrofit levels for heat pump installation in residential buildings.
Whereas the installation of a heat pump (HP) in new buildings is becoming rather common, electrifying the existing building stock remains a significant challenge. In particular, implementing low-temperature heating via HPs is often not feasible in dwellings with limited insulation and existing emitter systems. However, the growing market penetration of high-temperature heat pumps is reducing the stringency of insulation requirements. Previous studies have attempted to define the insulation threshold at which a dwelling can be considered ‘HP-ready,’ typically focusing on technical feasibility and energy cost. Yet, even when a dwelling meets these criteria, additional insulation may still be beneficial to reduce heat demand and optimize overall performance. This paper presents a multi-criteria analysis aimed at identifying optimal renovation strategies by examining the interplay between the building envelope and heating system, based on standardized calculations. Two representative Belgian dwellings are used as case studies, with varying initial conditions. For each initial state, suitable envelope renovation scenarios are developed, alongside detailed HP system designs. No alternative system variants, such as different heat pump models or photovoltaic panels, are considered. Both financial and CO2 indicators are calculated. Using Monte Carlo analyses, a robust set of insulation scenarios minimizing both financial and CO2 costs is identified, providing insights into cost effective and low-carbon renovation pathways for existing buildings.