Greenhills: A Zero-Energy Retrofit Achieving A1 Energy Performance
In 2024, we embarked on a comprehensive retrofit project at Greenhills, a neo-Georgian residence located just outside Kinsale. Originally built in the mid-1990s, this two-storey home sat at the base of rolling green fields that once served as a point-to-point racecourse. While its setting was undeniably picturesque, the building itself had begun to show its age. After 30 years of family life, wear and tear, and a lack of energy efficiency upgrades, it was clear that a deep retrofit was needed to bring the property in line with modern performance standards.
The Challenges
The house was originally rated C3 on the Building Energy Rating (BER) scale, a level typical of properties from its era but far below today’s sustainability expectations. With rising energy costs and ambitious national climate targets, the homeowners were eager to future-proof their property. The key challenges included:
Thermal Performance – The existing fabric was relatively inefficient, with poor insulation and air tightness.
Space & Layout – The interior layout did not fully take advantage of the stunning surrounding views.
Heating & Energy Systems – The home relied on outdated oil fired heating and ventilation systems that contributed to high running costs.
Aesthetic & Functional Upgrades – Beyond energy efficiency, the owners wished to modernise key living spaces, including the kitchen, living area, and attic.
The Retrofit Strategy
Our approach to transforming Greenhills was both holistic and ambitious. The project included:
Fabric First UpgradesTo dramatically improve thermal efficiency, we upgraded the building envelope with high-performance insulation, triple-glazed windows, and airtight construction methods. A full external wall insulation (EWI) system was installed, ensuring the structure met Passive House levels of air tightness.
High-Performance Heating & VentilationThe outdated oil-fired heating system was replaced with a air-source heat pump, paired with low temperature radiators for improved thermal comfort. A whole-house mechanical ventilation system with heat recovery (MVHR) was introduced to enhance indoor air quality while minimising heat loss.
Renewable Energy Generation
To achieve A1 energy performance, we installed a solar photovoltaic (PV) array with battery storage, significantly reducing reliance on grid electricity. This system was designed to complement the heat pump, ensuring year-round efficiency.
Extending & Reconfiguring Living Spaces
To maximise the home’s relationship with its landscape, we extended the building towards the open fields, creating a seamless connection between indoor and outdoor spaces. The kitchen and living area were reconfigured to enhance natural light and flow, making them the heart of the home. Additionally, the attic was converted into a functional space, increasing the property’s usable area.
Achieving an A1 Energy Rating
Through these measures, Greenhills successfully transitioned from a C3 to an A1 BER rating, verified in January 2025. This transformation not only future-proofed the home but also significantly reduced its carbon footprint, energy demand, and running costs. The project stands as a testament to the potential of deep retrofit strategies in upgrading Ireland’s housing stock to near zero-energy standards.
At RUA Architects, we continue to push the boundaries of sustainable retrofit design, demonstrating how even traditionally built homes can be transformed into high-performance, comfortable, and energy-efficient spaces for the future.

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