Specialist Passive House Consultancy

Passive House

Here at PL Architects we offer our clients specialist consultancy in Passive House architecture, if you have any inquiries into potential Passive House projects, please get in touch here.

Public awareness of the idea of “Passive House” and it’s potential to be an extraordinarily cost effective and environmentally sustainable option for future housing projects is surprisingly limited. As such, this page has been produced with the aim of informing potential clients of both the concept of Passive House and the compassing benefits that they can expect to gain through under taking such a project.

What is the Concept of Passive House?

The heat losses of the building are reduced so much so 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 PassivHaus.” – Prof. Dr Wolfgang Feist, Director of the Passive House Institute, Darmstadt, Germany.

(Source: PassivHaus Trust, https://www.passivhaustrust.org.uk/what_is_passivhaus.php Accessed 16 October 2021)

Built in Darmstadt-Kranichstein in 1988, the construction of the first “Passive House” was the first instance whereby the concepts of Wolfgang Feist, and engineer Bo Adamson, were put into practice. Passive House designs are built with the ambition that a building uses the minimum amount of energy required to maintain a comfortable living experience all year round. Feist’s concept of Passive House have been instituted within a set of specification requirements for a building before it can be certified as a Passive House. As listed, the international Passive House standard requirements are:

  • A space heat demand maximum of 15 kWh/m2a or a heating load maximum of 10 W/m2.
  • A pressurisation test result at 50 Pa maximum of 0.6 ACH (both over-pressure and under-pressure)
  • A total primary energy demand maximum of 12o kWh/m2a.

(Source: PassiveHouse Canada, https://www.passivehousecanada.com/about-passive-house/ Accessed 16 October 2021)

How is Passive House Achieved?

Passive House projects are intricately designed to achieve the reductions in energy use as per the requirements laid out by the Passive House standard. Predominantly therefore, projects are designed with these 5 key features in mind:

  • Triple-Glazed Windows: The use of glass with U-Values of 0.80W (m²K) or less Low-Emissivity (Low-E) glass, with Argon or Krypton gas between the panes.
  • Thermal Insulation: All walls and surfaces of the building effectively insulated with U-Values of 0.15 W/(m²K) or less.
  • Mechanical Ventilation Heat Recovery: A process whereby heat energy held within air exiting the building is transferred into fresh air entering.
  • Airtight Construction: The reduction of air leakage, therefore the loss of heat energy, through the removal of gaps and porous materials. Reducing leakage to less that 0.6 of the total house volume, per hour, at 50 Pascals pressure.
  • Thermal Bridging Elimination: Designed and constructed in a manner than reduces the amount of heat energy lost passively through unnecessary thermal bridging in traditional house designs.

(Source: Norrsken, https://www.norrsken.co.uk/sustainability/passive-houses? Accessed 16 October 2021)

A diagram showing the features of a Passive House in conjunction. (Source: Passive House Institute, https://passiv.de/en/02_informations/02_passive-house-requirements/02_passive-house-requirements.htm. Accessed 24 January 2022)

What are the Benefits of a Passive House?

Whilst we’ve established the concepts and practicalities of Passive House, we are yet to set out incentives for clients to undertake such a project. This is not, however, to say that benefits are in short supply.

Financial Benefits:

In the UK Passive House projects cost, on average, 8-10% more than traditional housing projects during construction. However, such initial costs are offset dramatically by the long-term reductions in energy bills.

OVO Energy has calculated that owners of Passive House owners spend, on average, just £50 on primary energy (heating, hot water and electricity) bills annually. In contrast, a Victorian built house would cost, on average, in the region of £1,000 annually. The vast contrast in annual energy costs means passive house owners will save large sums of money in the long term, helping to recuperate quickly initial extra costs in the construction process.

If you would like to read more on the economic benefits of Passive House, click here.

(Source: OVO Energy, https://www.ovoenergy.com/guides/energy-guides/passive-house, accessed August 19 2021)

Environmental Benefits:

Passive House buildings require far less energy to heat or cool the building than traditional housing. OVO Energy, for instance, has calculated that a Passive House requires just 15 kWh/m² of heating per square metre net floor surface per year, a notably small energy requirement when compared with the 300 kWh/m² of heating required in a Victorian building. Put simply, this means Passive House designs, on average, require 77% less energy for heating than traditional housing.

A graph comparing the heat loss and gain comparison in different types of housing. (Source: OVO Energy, https://www.ovoenergy.com/guides/energy-guides/passive-house. Accessed 24 January 2022)

In ecological terms, the reduction of energy requirements in Passive House projects equates to a reduction in the burning of non-renewable energy sources such as coal, oil and natural gas, meaning Passive Haus designs produce a far smaller carbon footprint than their traditional counterparts. According to the PassivHaus Trust, these reductions in energy use will significantly aid the housing industry in meeting their 2050 net zero carbon emission targets.

Further still, Passive House projects can be made to be environmentally sustainable through the consideration of construction materials. the distances materials must be transported can be considered, with local alternatives being utilised to reduce the carbon footprint of the project further.

If you would to read more on the environmental sustainability of Passive House, click here.

(Source: PassivHaus Trust https://www.passivhaustrust.org.uk/competitions_and_campaigns/passivhaus-and-zero-carbon/ Accessed 23 January 2022)

Health Benefits:

Lastly, but arguably the most importantly, the living standards provided by Passive House buildings provides notable improvements in the health of the occupants. The strict regulation of heat loss and air tight construction provides consistent air temperatures all year round, resulting in the removal of cold spots and damp, providing a healthier living environment for occupants. In addition, air regulation results in the removal of cold drafts, providing a more comfortable living environment for the occupant, promoting better mental health and a better work environment.

Any Passive House Questions? 

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