Passivhaus / Passive House design

As a Certified Passive House Designer we offer both new build and retrofit (EnerPHit) design and construction services in line with the International Passivhaus Standard for the delivery of Passive House buildings.

Passivhaus or Passive House Standard

With over 30 years of international evidence, the Passivhaus standard is a tried & tested solution for delivering net-zero-ready new and existing buildings optimised for a decarbonised grid. Passivhaus buildings provide higher levels of occupant comfort whilst using minimal energy for heating and cooling.

Passivhaus adopts a whole-building approach with clear, measured targets, focused on high-quality construction.

For a building to be considered a Passive House, it must meet the following criteria:

The Space Heating Energy Demand must not exceed 15 kWh per square meter of net living space (treated floor area) per year or 10 W per square meter peak demand.

The Renewable Primary Energy Demand (PER, according to PHI method), sets the total energy to be used for all domestic applications (heating, hot water and domestic electricity) at no more than 60 kWh per square meter of treated floor area per year for the Passive House Classic standard.

Airtightness targets must meet a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50), as verified with an onsite pressure test.

Thermal comfort must be met for all living areas during winter as well as in summer, with not more than 10 % of the hours in a given year reaching over 25 °C.

In order to achieve the above, five key principles need to be considered in unison:

Thermal insulation
All opaque building components of the exterior envelope must be extremely well insulated. For most cool-temperate climates, this means a heat transfer coefficient (U-value) of 0.15 W/(m²K) must be achieved.

Passive House windows
The window frames must be well insulated and fitted with low-e glazing filled with argon or krypton to minimise heat transfer. For most cool-temperate climates, this means a U-value of 0.80 W/(m²K) or less, with g-values of around 50%.

Ventilation heat recovery
Efficient heat recovery ventilation is key not only to facilitating good indoor air quality but also to save energy.

Airtightness
Uncontrolled leakage through gaps must result in less than 0.6 air changes per hour for the total house volume. This is achieved by carefully detailing and applying a continuous air tight layer.

Thermal bridges
All edges, corners, junctions and penetrations must be planned and executed with great care in order to avoid heat loss through thermal bridging. Thermal bridges which cannot be avoided must be minimised as far as possible.

EnerPHit - the retrofit standard

EnerPHit is a slightly relaxed standard for retrofit projects, where the existing architecture and conservation issues mean that meeting the Passivhaus standard is not feasible. The use of Passivhaus components in refurbishments results in a considerable improvement to thermal comfort, economic efficiency, and improved protection of the existing structure.

Improvements in line with this standard have demonstrated reductions in heating energy demand of up to 90%.

Interested in learning more about Passivhaus/ Passive House and whether it is the right approach for you?