Why Energy Efficiency Standards Matter in Ireland.
Energy efficiency rules are not optional extras. They directly affect:
- How much you pay to heat your home
- Whether a home meets current planning and building regulations
- Long-term comfort and health
- Resale value
In Ireland, these standards have tightened significantly over the last decade.
New homes are designed around energy scarcity and climate targets because cheap, abundant energy can no longer be assumed. Older homes, on the other hand, were built around cheap energy.
Energy costs are volatile, fossil fuel use is being reduced, and national climate targets now shape how homes are designed and approved.
With this in mind, Ireland has committed to:
- A large 51% reduction in national carbon emissions by 2030
- A long-term shift away from fossil fuels
- Lower energy demand across buildings, transport, and industry
Homes matter because residential buildings account for about 24% of energy use and emissions. Improving efficiency at the point of construction is far easier and cheaper than fixing problems later.
1. Nearly Zero Energy Building Standards (NZEB).
All new homes built from Jan 2021 in Ireland must meet NZEB standards.
This means the home:
- Uses very little energy overall
- Produces some of that energy from renewable sources such as wind or solar energy
- Is highly insulated and airtight
NZEB does not mean zero energy bills. It simply means that energy demand is kept as low as possible before renewables are added.
What does NZEB Look Like in Practice?
For all new builds, NZEB is equivalent to a 25% improvement in energy performance on the 2011 Building Regulations.
To meet NZEB, a home usually includes:
- High levels of insulation (walls, roof, floors)
- Triple or high-performance double glazing
- Airtight construction
- A heat pump system
- Solar panels (PV)
Smaller homes benefit most from NZEB because:
- Less space to heat
- Lower absolute energy demand
- Easier compliance
This is one reason modular and compact homes perform well under NZEB rules.
2. Part L of the Building Regulations.
Part L is the legal backbone behind NZEB. It sets mandatory standards for energy use, insulation, ventilation, and carbon emission reductions in new and renovated buildings.
Part L applies to:
- New homes
- Major renovations
- Extensions over a certain size
So to summarise, Part L is the rulebook. NZEB is the outcome.
Key Aspects of Part L include (2019/2021/2025 updates):
- Boiler Replacements – Replaced heating systems must meet high-efficiency standards, with a push to move away from fossil fuels in renovations.
- NZEB Standards – New homes must achieve top-tier energy performance (typically A2/A3 BER), with most energy use covered by renewables.
- Renewable Energy – renewable sources, such as solar PV or heat pumps, must meet 20% of the energy demand.
- Thermal Performance – Strict maximum
𝑈-values for walls, roofs, and windows are required to minimize heat loss, with 2023 guidelines pushing for 0.18 or lower for many elements.
- Airtightness – Stringent testing is required to minimize air leakage, crucial for energy efficiency.
- Major Renovations – If >25% of the building envelope is renovated, the entire building must meet specific energy performance standards, often leading to A3 BER targets.
Homes must prove compliance through:
- Energy calculations
- On-site inspections
- Airtightness tests
This applies equally to traditional and non-traditional builds.
3. BER Ratings
The Building Energy Rating (BER) is a label from A to G.
This is how energy ratings in homes are scored, with A being the most energy-efficient and G being the least energy-efficient.
What the Ratings Mean
- A-rated – Very low running costs
- B-rated – Efficient, but older or lightly upgraded
- C–D – Average Irish homes
- E–G – High energy bills, poor insulation
All new NZEB homes typically achieve A2 or A3 ratings.
BER ratings also affect:
- Mortgage approvals – Lenders favour energy-efficient homes because lower running costs reduce financial risk and improve long-term affordability for buyers.
- Buyer demand – Homes with higher energy ratings can be more attractive because they offer lower bills, better comfort, and stronger resale value.
- Retrofit grant eligibility – Many State grants require minimum energy improvements, meaning poorly rated homes often need upgrades before financial support becomes available, i.e heat pump upgrades for example
3a. Airtightness
Airtightness is a part L requirement that measures how much air leaks out of a home. Poor airtightness means that heat escapes, cold air enters and heating systems work harder.
- Testing requires a maximum air permeability of≤5 m3/(h⋅m2) at 50 Pa.
- A test must be conducted upon completion of the building, with stricter standards (<3 m3/(h⋅m2)) recommended for systems using Mechanical Heat Recovery Ventilation (MHRV). ENERRating.
Key Requirements and Standards
- Procedure – A “blower door” test is used, typically at the end of construction, to ensure air sealing around doors, windows, and service penetrations.
- Target Level – The current maximum allowable limit is
5 m3/(h⋅m2) at 50 Pa.
- MHRV Requirement – For homes with Mechanical Ventilation with Heat Recovery, it is recommended to achieve an air permeability rate of less than 3m3/(h⋅m2).
- Mandatory Testing – Mandatory for new dwellings and many commercial buildings (especially over
).
- Sampling – For large developments, specific percentages of homes must be tested (e.g., 2-5% for large projects), though many builders test 100% to avoid compliance risks.
- Methodology – Tests must be performed according to European Standard EN 13829.
3b. Ventilation Standards
As homes become more airtight, ventilation becomes essential.
In Ireland, all new dwellings and major renovations require independent ventilation validation to comply with TGD Part F (2019) and NZEB standards. Systems must be installed by a competent person, and a certified validator must test that airflow rates meet design specs.
If air permeability is <3 m3/(h.m2), mechanical ventilation is mandatory.
Key Requirements & Compliance
- Mandatory Testing – Every new dwelling must have its ventilation system commissioned, balanced, and verified.
- Validator Competence – Testing must be completed by a qualified “Ventilation Validator” registered with the National Standards Authority of Ireland (NSAI).
- TGD Part F 2019 Compliance – Systems must satisfy the minimum requirements for airflow, controls, and installation, often following I.S. EN 14134: 2019.
- Airtightness Link – If the air permeability is below
3 m3/(h.m2) at 50Pa (common in new builds), natural ventilation is insufficient; mechanical extract (MEV) or heat recovery (MVHR) is required.
- Documentation – A Ventilation Validation certificate confirming compliance must be provided.
Heat Pumps and Energy Standards
Heat pumps are now the standard heating system for new homes.
They:
- Use electricity instead of fossil fuels
- Work best in well-insulated homes
- Deliver low running costs when paired with NZEB design
It appears that fossil fuel heating is being phased out, as CSO data shows that 95% of new dwellings in 2023 featured electric heating systems, primarily air-to-water heat pumps. Gov.ie
For more on heat pumps, read HERE.
Final Words & Common Misunderstandings
- NZEB does not mean free energy
- Solar panels alone do not make a home compliant
- Small homes still need proper insulation
- Energy rules are legal requirements, not guidelines
Understanding this early avoids expensive redesigns later. Ireland’s energy efficiency standards are strict, but they exist for clear reasons:
- Lower energy use
- Lower emissions
- More comfortable homes and
- Reduced long-term costs
For first-time buyers and those exploring non-traditional housing, these standards are not barriers; they are design rules that reward smaller, smarter homes.
Understanding them properly is one of the best ways to avoid costly mistakes.
