CASE STUDY
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.
€19,200 SEAI Grant Secured
Full Project Management
Gas Eliminated
BEFORE
D1
245
kWh/m²/yr
49.92
kgCO₂/m²/yr
AFTER
A1
-16.55
kWh/m²/yr
-2.12
kgCO₂/m²/yr
261.55 kWh/m²/yr
improvement in energy performance
A1
New BER Rating
D1
Previous BER Rating
€19,200
SEAI Grant Secured
€22,680
Client Net Cost
€41,880
Total Project Value
125.63m²
Floor Area
10 wks
Mar to May 2025
-52
kgCO₂/m²/yr Improvement
THE STORY
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.
Why this project stands out
- BER improved from D1 to A1
- Energy value improved by 261.55 kWh/m²/yr
- Gas central heating was replaced
- €19,200 in SEAI grants secured
- Full project management from survey to sign-off
- Completed in under ten weeks
THE PERFORMANCE UPLIFT
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 |
261.55
kWh/m²/yr Improvement
A whole-home retrofit delivered measurable improvement in efficiency, comfort, and carbon performance.
SCHEDULE OF WORKS
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.
PROJECT GALLERY
See the Retrofit in Progress
A visual selection of key stages throughout the retrofit project.
Windows/pipework at back
New Front Door
Hot Water Cylinder
REAL-WORLD IMPACT
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
€
€555
saved over a comparable 9-week period
Electricity 9-week period, before
€470
electricity only
Gas same period, before
€325
now eliminated
Combined energy 9-week, before
€795
electricity + gas
Electricity same 9-week period, after
€240
no gas bill at all
CLIENT REVIEW
★★★★★
“I had a very good experience with REIL. The service was quick, efficient and well organised. Everything was handled professionally, and I had no issues. I am very satisfied and would highly recommend.”
T
Mr Thomas
Raheen, Co. Limerick
CONCLUSION
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.
HOW REIL MAKES IT SIMPLE
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.
1
Initial Assessment
REIL assesses the home and identifies the right whole-home upgrade pathway.
2
Retrofit Plan
A coordinated upgrade plan is created across fabric, heating, and grant requirements.
3
Grant Management
SEAI grant administration is managed as part of the overall project process.
4
Installation
The building fabric, heating system, and supporting works are coordinated together.
5
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.