A passive house (or Passivhaus, from the original German) is not a type of house – it is a building standard. It is the most rigorous voluntary energy efficiency standard in the world, designed to reduce a building’s heating demand to an absolute minimum while maintaining excellent indoor comfort and air quality.
The name “passive” refers to the approach: instead of relying on large, energy-hungry heating or cooling systems (active systems), a passive house keeps itself warm primarily through superinsulation, airtightness and heat recovery from ventilation, sunlight and even the body heat of occupants and appliances. The building itself does most of the work – passively.
The standard applies to all building types, not just houses. Schools, offices, hospitals, apartment blocks and leisure centres can all be designed or certified to the Passive House standard.
📐 What Are the Passive House Requirements?
To be certified as a Passive House, a building must meet specific performance criteria set by the Passive House Institute (PHI) in Darmstadt, Germany. The key requirements are:
- 🌿 Heating demand: No more than 15 kWh/m² per year, or a peak heat load of no more than 10 W/m². For a typical 150 m² Irish home, that means a maximum of 2,250 kWh per year for heating – compared to the average Irish household gas consumption of around 11,000 kWh.
- 🌿 Total primary energy: No more than 120 kWh/m² per year (covering heating, hot water and electricity combined). Updated classes (Passive House Plus and Passive House Premium) set even lower targets and require renewable energy generation.
- 🌿 Airtightness: Air leakage must not exceed 0.6 air changes per hour at 50 pascals of pressure (tested using a blower door test). This is roughly ten times more airtight than current Irish building regulations require.
- 🌿 Thermal comfort: Indoor temperatures must remain comfortable year-round, with no more than 10% of hours in any year exceeding 25°C.
These are performance targets, not prescriptive rules. There is no single way to build a passive house – architects and engineers have freedom to choose materials and methods, as long as the finished building hits the numbers.
🏗️ The Five Principles of Passive House Design
Every passive house is built around five core principles. These work together as a system – remove any one and the standard becomes much harder to achieve.
🧱 1. Superinsulation
Walls, roof and floors are insulated far beyond standard building regulations. In Ireland, a passive house typically needs U-values of around 0.15 W/m²K or lower for walls, roof and floors. That translates to roughly 280 mm of insulation in walls and 330 mm in roofs – compared to the 100-150 mm you might find in a standard new build. The insulation must be continuous, with no gaps or breaks, to prevent thermal bridges where heat can escape.
🪟 2. High-Performance Windows
Passive houses use triple-glazed windows with Low-E coatings and argon or krypton gas between the panes. These windows achieve U-values of 0.8 W/m²K or lower – far better than the 1.6 W/m²K maximum required by building regulations for replacement windows. The frames are insulated too, and windows are strategically positioned to maximise solar heat gain in winter while minimising overheating in summer.
🌬️ 3. Airtightness
An airtight building envelope prevents uncontrolled drafts and heat loss. This is tested during construction using a blower door test, which pressurises the building to find and fix leaks before completion. Airtightness is what makes the insulation work properly – you can have thick insulation, but if the building is full of gaps and cracks, warm air escapes and cold air gets in regardless.
♻️ 4. Mechanical Ventilation with Heat Recovery (MVHR)
Because a passive house is so airtight, you cannot rely on opening windows or wall vents for fresh air (though you can still open windows whenever you want to). Instead, a mechanical ventilation system constantly supplies fresh, filtered air while extracting stale air. The clever part is the heat recovery unit, which captures up to 90% of the heat from outgoing air and transfers it to the incoming fresh air. You get constant clean air without losing heat.
This is often the feature that surprises people most. Far from being stuffy, passive houses typically have better air quality than conventional homes – the filtered air reduces dust, pollen, pollution and moisture issues.
🌞 5. Thermal Bridge-Free Design
Thermal bridges are points in a building where heat bypasses the insulation – for example at window frames, wall junctions or where a balcony penetrates the building envelope. In conventional construction, these can account for significant heat loss. Passive house design eliminates or minimises thermal bridges through careful detailing at every junction.
🇮🇪 Passive House in Ireland
Ireland’s mild maritime climate – wet but rarely extremely cold – actually makes it an excellent location for passive houses. The moderate winter temperatures mean less insulation is needed to hit the 15 kWh/m² target than in colder northern European countries. Ireland also has one of the largest pools of trained passive house designers and tradespeople in the world relative to its population.
The Passive House Association of Ireland (PHAI) promotes the standard and organises training for architects, engineers and builders. The Royal Institute of the Architects of Ireland also provides a certified European Passive House Designer course accredited by the Passive House Institute.
In a landmark decision, Dún Laoghaire-Rathdown County Council became one of the first local authorities in the world to require all new homes to be built to Passive House standard or equivalent performance where reasonably practical. While enforcement varies, the policy signalled the direction of travel for Irish construction.
📊 Passive House vs Irish Building Regulations
Current Irish building regulations (Part L 2021 and the NZEB – Nearly Zero Energy Building standard) already require new homes to be significantly more efficient than those built even ten years ago. However, a certified Passive House still goes well beyond NZEB requirements. According to the PHAI, passive houses use up to 90% less energy for heating compared to a home built to current regulations, and annual running costs can be over 70% lower.
From 2030, all new buildings in the EU must be zero-emission buildings (ZEB). As regulations continue to tighten, the gap between standard new builds and the Passive House standard will narrow – which is why many architects and self-builders in Ireland view building to Passive House standard now as future-proofing their homes against regulations that are coming anyway.
💰 What Does a Passive House Cost?
The premium for building to Passive House standard in Ireland is typically estimated at 5-15% above the cost of a standard building regulations-compliant build. This varies depending on the design, site and contractor experience. The premium covers thicker insulation, higher-specification windows, the MVHR system and more rigorous detailing and testing.
However, passive houses have dramatically lower running costs. With heating demand cut by up to 90%, energy bills can be as low as €1 per square metre per year for heating. Over the lifetime of the building, the energy savings far outweigh the initial premium. Property value is also positively affected – an A-rated home commands a higher price than a lower-rated equivalent.
🔧 Can You Retrofit a Home to Passive House Standard?
The Passive House Institute developed the EnerPHit standard specifically for retrofits. EnerPHit has slightly relaxed targets (heating demand of 25 kWh/m² and airtightness of 1.0 air changes per hour) to reflect the practical constraints of working with existing structures.
Achieving EnerPHit on an existing Irish home requires significant work – external insulation, new windows, an MVHR system, and careful attention to airtightness and thermal bridges. It is more expensive and complex than a standard retrofit to BER B2, but delivers a far higher level of performance and comfort. SEAI grants cover many of the individual measures involved, and the One Stop Shop scheme can manage the process.
🔗 How Passive House Connects to Other Climate Terms
- 🌿 U-value – passive houses require U-values of 0.15 W/m²K or lower, far beyond standard regulations
- 🌿 BER rating – passive houses achieve A ratings, the highest on the BER scale
- 🌿 Retrofitting – the EnerPHit standard adapts passive house principles for existing buildings
- 🌿 NZEB – Nearly Zero Energy Buildings are the current regulatory standard; passive house exceeds them significantly
- 🌿 Heat pumps – passive houses need such little heating that a small heat pump is often sufficient for the entire building
- 🌿 Solar panels – adding solar PV to a passive house can make it net zero or even energy-positive
- 🌿 Energy poverty – passive house standard eliminates energy poverty by design, as running costs are negligible
❓ Frequently Asked Questions
Is a passive house the same as a zero-carbon house?
Not exactly. A passive house focuses on minimising energy demand through the building fabric and ventilation. A zero-carbon house goes further by ensuring that any remaining energy use produces no net carbon emissions, usually by generating renewable energy on site. However, passive houses are very easy to make zero-carbon because their energy demand is so low – adding solar panels is often all it takes.
Are passive houses stuffy or hard to ventilate?
No. This is the most common misconception. Passive houses have better air quality than conventional homes because the MVHR system provides a constant supply of fresh, filtered air. You can still open windows whenever you like – the ventilation system simply ensures good air quality at all times, even when windows are closed.
Do passive houses work in Ireland’s climate?
Ireland is actually one of the best climates in Europe for passive house construction. The mild winters mean less insulation is needed to meet the standard compared to colder countries like Germany or Scandinavia. Ireland also receives useful solar heat gain even in winter. The PHAI notes that Ireland has a large and growing pool of trained passive house professionals.
Can I get a grant for building a passive house?
SEAI grants cover many of the individual components used in passive house construction, including insulation, heat pumps, solar panels and ventilation systems. There is no specific “passive house grant,” but the combination of available grants can significantly reduce the premium cost. For retrofits to EnerPHit standard, the One Stop Shop scheme can coordinate the process and maximise grant uptake.