From D1 to Energy Positive A1 in Under Ten Weeks
A semi-detached home in Raheen, Co. Limerick was transformed from a D1-rated property into an A1 energy-positive home through a fully managed REIL whole-home retrofit.
From a Standard D1 Home to an A1 Energy-Positive Property
Mr Thomas’s semi-detached home in Raheen, Limerick arrived to REIL as a standard D1-rated property. It was solid but inefficient, reliant on gas central heating and poorly insulated against the Irish climate.
He wanted to reduce running costs, improve comfort, and future-proof the property for his family.
REIL delivered a fully coordinated retrofit package covering the building fabric, heating system, and grant management from start to finish. Works began on 3rd March 2025 and were completed by 7th May 2025, with the full whole-home retrofit completed in under ten weeks.
The result exceeded all expectations. The property now holds an A1 BER with an energy value of -16.55 kWh/m²/yr, making it genuinely energy positive and producing more energy than it consumes on a calculated basis.
The project was fully managed by REIL, including SEAI grant administration, and Mr Thomas was supported throughout every stage with a single point of contact from survey to sign-off.
Before and After Results
| Measure | Before | After |
|---|---|---|
| BER Rating | D1 | A1 |
| Energy Value | 245 kWh/m²/yr | -16.55 kWh/m²/yr |
| Carbon Emissions | 49.92 kgCO₂/m²/yr | -2.12 kgCO₂/m²/yr |
| Heating System | Gas central heating | Air source heat pump |
| Energy Position | Inefficient D-rated property | Energy-positive A1 property |
kWh/m²/yr Improvement
A whole-home retrofit delivered measurable improvement in efficiency, comfort, and carbon performance.
A Whole-Home Retrofit Package
REIL delivered a coordinated upgrade across the building fabric, heating system, and grant management process.
Cavity Wall Insulation
Cavity wall insulation was installed throughout the property to significantly reduce heat loss through the external walls, one of the primary sources of energy waste in Irish homes of this era.
Roof Insulation, Ceiling Level
Insulation was installed at ceiling level to prevent heat escaping through the roof. Combined with the wall treatment, this dramatically improved the thermal envelope of the home.
External Windows
New high-performance external windows were installed across the property to reduce heat loss, eliminate draughts, and improve acoustic comfort and overall thermal performance.
External Doors ×2
Two external doors were replaced with energy-efficient units to close remaining gaps in the building’s thermal envelope and improve airtightness at entry points.
Air Source Heat Pump
A new air source heat pump was designed and installed to replace the existing gas boiler, providing both space heating and hot water. The full central heating system was upgraded to work optimally with the heat pump.
Heat Pump Bonus & Project Management
The project was fully managed by REIL from initial assessment through to final grant drawdown, including securing the SEAI Heat Pump Launch Bonus.
The Numbers That Matter
Comparing the same 9-week period year-on-year, Mr Thomas’s total energy spend dropped from €795 to €240. This created a saving of €555 over that window alone.
Gas costs have been eliminated entirely following the heat pump installation.
What This Project Demonstrates
This project is a clear example of what is achievable when fabric improvements and low-carbon heating are delivered together as one coordinated package.
A D1-rated home, common across Irish housing stock of this type, has been transformed into an energy-positive A1 property, with carbon emissions moving from 49.92 to -2.12 kgCO₂/m²/yr.
For a net client investment of €22,680 after grants, Mr Thomas now has a warmer, healthier home with dramatically lower running costs and no reliance on gas.
One Managed Process From Survey to Sign-Off
Mr Thomas had a single point of contact throughout and was not required to manage contractors, applications, or compliance separately.
Initial Assessment
REIL assesses the home and identifies the right whole-home upgrade pathway.
Retrofit Plan
A coordinated upgrade plan is created across fabric, heating, and grant requirements.
Grant Management
SEAI grant administration is managed as part of the overall project process.
Installation
The building fabric, heating system, and supporting works are coordinated together.
Sign-Off
The completed project delivers an A1 BER and an energy-positive result.
Could Your Home Achieve a Similar Upgrade?
REIL manages the full home energy upgrade process, from assessment and retrofit planning to SEAI grants, installation, and final BER.