Colm Donaghy
Colm DonaghyColm Donaghy

Passive House

In March 2013 Colm Donaghy qualified as a Certified Passive House Designer and is now registered with the Passivhaus Institut, Darmstadt, Germany. 

Architect Armagh - Architects Dungannon

The following is an overview of the Passive house standard.

The Passive House Standard
Passivhaus or 'Passive House' is the world's fastest growing energy performance building standard. It can be used to produce any building type not just houses and certification is available for both new-build and retrofit projects.

Passive House was developed in Germany in the 1990s by Professors Bo Adamson and Wolfgang Feist and is a 'fabric first' approach to constructing low energy buildings.

The primary focus of the Passive House standard is to greatly reduce the requirement for space heating and cooling within a building, whilst creating both excellent air quality and increased comfort levels.

Reasons for building to Passive house standard
Passive house buildings achieve a 75% reduction in space heating requirements, compared to standard practice for UK and Irish new build.

Incoming air is filtered to take out pollutants and then heated or cooled to provide a constant supply of comfortable clean air that has an ideal relative humidity.

Passive house is a 'fabric first' construction type and as such doesn't rely on elaborative gadgetry to maintain comfort levels. Passive house can be built with or without the use of renewable energy components.

Passive house construction is estimated to cost approximately 10-15% more than standard construction however with running costs greatly reduced and comfort levels heightened it is money well spent. 

“The heat losses of the building are reduced so much that it hardly needs any heating at all. Passive heat sources like the sun, human occupants, household appliances and the heat from the extract air cover a large part of the heating demand. The remaining heat can be provided by the supply air if the maximum heating load is less than 10W per square metre of living space. If such supply-air heating suffices as the only heat source, we call the building a Passive House.”

Prof. Dr Wolfgang Feist Head of Energy Efficient Construction/Building Physics at the University of Innsbruck, Austria and Director of the Passive House Institute, Darmstadt, Germany.

The Passivhaus Institute in Germany has developed a series of certification processes to ensure the quality of official Passive House buildings and practitioners. A number of UK and Irish organisations have been approved to assess and issue the Quality Assured Passivhaus Certificates for new-build projects and Ener-fit Certificates for retrofit schemes.

Passive House Principles

Passive House Five Principles
Passive House Five Principles
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Passive House Five Principles
Thermal insulation
All opaque building components of the exterior envelope of the house EG walls, roof & floor construction are so well-insulated that they have a heat transfer coefficient (U-value) of 0.15W/m²K at the most, i.e. a maximum of 0.15 watts per degree of temperature difference per square metre of exterior surface are lost.

Thermal Bridge Free Construction
No full or partial penetration of the insulated envelope by materials with different thermal conductivities (lamda values) or no change in thickness of a material.
Basic rules - avoid piercing the thermal envelope, if unavoidable use materials with lowest possible lamba values.
Connection - no gaps in thermal envelope.
Geometry - choose edges with angles that are blunt

Passive House windows
The U-value of a Passive House window should not exceed 0.80 W/m²K (un-installed). This invariably means triple glazing.

U-value is a measure of heat loss in a building element. A low U-value indicates high levels of component insulation.

In most cases passive house projects will have large glazed areas with summer shading to the south elevation however with good design and modern glazing types it is possible to reduce the glazed south facade to 25-35%.

Glazing to the North facade is minimized due to issues with heat loss. As a result habitable rooms are ideally located to the southern aspect with service rooms/bathrooms etc sited to the north.

Mechanical heat recovery ventilation
The MHRV system provides highly effective heat recovery along with excellent indoor air quality and can also be used to heat or cool the building depending on specific requirements.

At least 75% of the heat from the exhaust air is transferred to the fresh air by means of a heat exchanger in the MHRV unit.

Air tightness
Excellent air tightness levels achieved through rigorous design and installation practices prevent uncontrolled air leakages from or into the building. At a pressure/de-pressure of 50 pascals no more than 0.6 of the total house volume per hour is allowed to escape/infiltrate. This greatly exceeds current building regulation standards.