Case Study:
A2 homes ready for renewable gas

Cluain Beag development achieves NZEB standards with natural gas.

Supporting developers to achieve NZEB standards with natural gas

Part L (NZEB) of the Building Regulations require new residential buildings to have a very high energy performance. The low amount of energy (nearly zero) that these buildings require should, to a significant extent, come from renewable sources produced on-site or nearby.

Cluain Beag is William Neville & Sons’ latest new housing development that combines natural gas with solar photovoltaic (PV) panels and energy efficient designs to ensure each home has an A2 BER rating and meets Part L (NZEB) of the Building Regulations.

If you wish to explore how you can achieve NZEB standards for your planned development and provide your customers all the benefits of natural gas, please contact us today for a free consultation.

Book a free consultation

Ready for renewable gas

Ireland’s gas network is a vital national asset that generates over 50% of Ireland’s electricity. Today, more than 680,000 Irish homes rely on the gas network to provide safe and reliable energy to meet their heating, cooking and power needs. By gradually replacing natural gas with renewable, carbon neutral and ultimately zero carbon gases, such as biomethane and hydrogen, these same homes and more will be powered by increasingly cleaner energy.

Biomethane, which began flowing on the network in 2019, is the first step on this journey. Produced from agricultural and food waste, this renewable gas is structurally identical to natural gas and can be used in exactly the same way through the existing infrastructure, boilers and appliances, meaning homeowners will transition to this carbon neutral energy and play their part in progressing Ireland towards a cleaner energy future, without changing a thing. By connecting new homes and developments to the gas network today, you are ensuring that each homeowner will have reliable and cleaner energy keeping them and their families safe, warm and comfortable for generations to come.

Increased Thermal Bridging Factor performance

William Neville & Sons are committed to quality design and construction standards, focusing on key areas of the build process to ensure heat loss from the building fabric is minimised. This includes rigidly maintaining the necessary construction practices as laid out in the Acceptable Construction Details (ACDs). By following these guidelines, a non-default value of 0.08 W/m2K can be entered for the Thermal Bridging Factor into DEAP. This is then further enhanced by completing a desktop calculation of the linear thermal bridges throughout the dwelling, improving the final figure to 0.06 W/m2K.

“Natural gas remains the energy source of choice, as we know our prospective homeowners will be able to continue to decarbonise their homes into the future using renewable gas.”

William Neville
Director and Engineer, William Neville & Sons

System Features and Building fabric

91% efficient boiler

A Baxi Potterton gas boiler operates at 91% efficiency. This highly efficient boiler includes zone control for 3 heating zones supporting the homeowner to manage their energy bills.

Four solar photovoltaic panels

Photovoltaic systems convert solar energy into free electricity. These high efficiency panels operate all year round ensuring the are not restricted to the periods of warm weather.


Higher levels of insulation ensure greater thermal comfort and lower energy bills for homeowners. Pumped, bonded bead cavity wall insulation provides a uniform insulation barrier around the home.

Building fabric and performance coefficients

The figures below outline the performance of the building when assessed using the Dwelling Energy Assessment Procedure (DEAP) and demonstrates compliance with Part L (NZEB), achieving the required A2 standard.

Building Energy Rating ParametersActualPart L (NZEB) Requirement
Floor U-Value W/m2K 0.17 0.18
Wall U-Value W/m2K 0.18 0.18
Roof U-Value 0.14 0.16
Window U-Value 1.20 1.40
Door U-Value 1.40 1.40
Air Permeability m3/hr/m2 3 5
Thermal Bridging Factor W/m2K  0.06 0.08
Carbon Performance Coefficient (CPC) 0.265 0.35
Energy Performance Coefficient (EPC) 0.30 0.30
Renewable Energy Ratio (RER) 0.29 0.20
Boiler Efficiency 0.91 0.90

Benefits of solar PV panels

Lower energy bills

On average, a solar PV system can save between €200 - €300 per year on a domestic electricity bill (SEAI 2020).

Operate all year

Modern, high efficiency solar PV panels operate all year round, ensuring the benefits to the homeowner are not restricted to the summer period.

Reduced emissions

Generating renewable electricity will mean the energy consumed will be clean therefore reducing greenhouse gas emissions.

Cluain Beag case study - PDF

Book a free consultation

If you wish to explore how you can achieve NZEB standards for your planned development and provide your customers all the benefits of natural gas, please contact us today for a free consultation.

Book a free consultation