What is the difference between a passive house and a new build under today's regulations?

Since January 2021, every new building in Slovakia must meet the nearly zero-energy building (nZEB) standard, which corresponds to energy class A0. A passive house goes beyond that obligation: it strictly limits heating demand (≤ 15 kWh/m² per year), airtightness and thermal bridges, and verifies them by measurement rather than calculation alone. The gap in consumption between a passive house and a current new build is therefore much smaller than the gap against an older, uninsulated house.

Does a passive house have to be certified to be called one?

Certification is issued by the Passive House Institute after the design has been verified and the finished building measured. Without certification you can still build a house that meets the parameters, but formally it is a house 'built to passive standard', not a certified passive house. Certification is mainly worth it as an independent quality check on the design and the workmanship.

What are the Passive House Classic, Plus and Premium classes?

All three share the same envelope and airtightness requirements and differ only in how much renewable energy the building generates. Classic requires no on-site generation, Plus requires roughly as much energy as the building consumes, and Premium roughly twice that, i.e. a net surplus.

How much more expensive is a passive house than an ordinary new build?

The extra cost comes mainly from insulation thickness, window quality, detailing without thermal bridges, and the heat recovery unit. The precise figure depends on the design, the size of the house and the materials chosen, so compare real quotes for the same house rather than percentages quoted in articles. I cover the payback question in a separate article on whether a passive house is worth it.

Does a passive house overheat in summer?

Not if shading is designed in from the start. Large south-facing glazing without overhangs, blinds or other external shading will overheat any house, and a passive one all the faster because heat escapes from it slowly. External shading, night ventilation and sufficient thermal mass are part of the design, not an add-on.

Can you open the windows in a passive house?

Yes. Heat recovery ventilation removes the need to ventilate through windows, not the option to do so. In summer, night ventilation through open windows is in fact useful. Airtightness refers to uncontrolled leaks in the construction, not to keeping windows shut.

Can an existing house be converted into a passive house?

Meeting the criteria in full is difficult in an older building, because airtightness and the removal of thermal bridges are hard to achieve in an existing structure. The realistic goal of a deep renovation is to come substantially closer to the standard, which is what the separate EnerPHit certification standard for retrofits is designed for.

What is a Passive House?

March 15, 20245 min read

A timber-frame wall build-up with mineral wool between the studs and airtight tape sealing a joint

A passive house is a building standard that defines buildings with extremely low energy requirements for heating and cooling. This concept originated in Germany in 1988 and is now a recognized standard worldwide.

Core Principles

1. Excellent Thermal Insulation

The envelope of a passive house must have very low thermal transmittance (U-value). Typical values are:

Walls: U ≤ 0.15 W/(m²·K)
Roof: U ≤ 0.10 W/(m²·K)
Floor: U ≤ 0.15 W/(m²·K)

2. Elimination of Thermal Bridges

Thermal bridges are areas in the building envelope where increased heat loss occurs. In a passive house, all details must be designed to prevent thermal bridges.

A wall-to-roof junction under construction, with insulation carried unbroken up the wall and over the wall head — A continuous insulation layer is the principle that decides whether the other four work. Every break at a junction is a thermal bridge.

3. Airtightness

The building must be airtight to prevent uncontrolled heat losses. The maximum permissible airtightness value is n50 ≤ 0.6/h, verified by a blower door test.

4. Heat Recovery Ventilation

Ventilation is provided by a controlled system with heat recovery (recuperation). The heat recovery efficiency must be at least 75%.

5. High-Quality Windows

Windows must have triple glazing with Uw ≤ 0.8 W/(m²·K) and must be properly oriented for maximum solar gains.

Certification Criteria

For a building to receive Passive House certification, it must meet these criteria:

Heating demand: ≤ 15 kWh/(m²·year)
Primary energy demand: ≤ 120 kWh/(m²·year)
Airtightness: n50 ≤ 0.6/h

Benefits of Passive Houses

Minimal energy costs - savings of up to 90% compared with older, uninsulated building stock; compared with a new build meeting the nearly zero-energy building standard, mandatory for all new buildings in Slovakia since January 2021, the difference is considerably smaller
High thermal comfort - uniform temperature in all rooms
Indoor air quality - fresh filtered air
Resilience against energy price fluctuations
Lower carbon footprint

Conclusion

A passive house is not just a technical standard - it is a building design philosophy that respects the environment while providing a high quality of living.

Frequently asked questions

What is the difference between a passive house and a new build under today's regulations?: Since January 2021, every new building in Slovakia must meet the nearly zero-energy building (nZEB) standard, which corresponds to energy class A0. A passive house goes beyond that obligation: it strictly limits heating demand (≤ 15 kWh/m² per year), airtightness and thermal bridges, and verifies them by measurement rather than calculation alone. The gap in consumption between a passive house and a current new build is therefore much smaller than the gap against an older, uninsulated house.
Does a passive house have to be certified to be called one?: Certification is issued by the Passive House Institute after the design has been verified and the finished building measured. Without certification you can still build a house that meets the parameters, but formally it is a house 'built to passive standard', not a certified passive house. Certification is mainly worth it as an independent quality check on the design and the workmanship.
What are the Passive House Classic, Plus and Premium classes?: All three share the same envelope and airtightness requirements and differ only in how much renewable energy the building generates. Classic requires no on-site generation, Plus requires roughly as much energy as the building consumes, and Premium roughly twice that, i.e. a net surplus.
How much more expensive is a passive house than an ordinary new build?: The extra cost comes mainly from insulation thickness, window quality, detailing without thermal bridges, and the heat recovery unit. The precise figure depends on the design, the size of the house and the materials chosen, so compare real quotes for the same house rather than percentages quoted in articles. I cover the payback question in a separate article on whether a passive house is worth it.
Does a passive house overheat in summer?: Not if shading is designed in from the start. Large south-facing glazing without overhangs, blinds or other external shading will overheat any house, and a passive one all the faster because heat escapes from it slowly. External shading, night ventilation and sufficient thermal mass are part of the design, not an add-on.
Can you open the windows in a passive house?: Yes. Heat recovery ventilation removes the need to ventilate through windows, not the option to do so. In summer, night ventilation through open windows is in fact useful. Airtightness refers to uncontrolled leaks in the construction, not to keeping windows shut.
Can an existing house be converted into a passive house?: Meeting the criteria in full is difficult in an older building, because airtightness and the removal of thermal bridges are hard to achieve in an existing structure. The realistic goal of a deep renovation is to come substantially closer to the standard, which is what the separate EnerPHit certification standard for retrofits is designed for.