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Passive House, Low Energy Design & NZEB

What is a Passive House?


A building standard that is truly energy efficient, comfortable, affordable and ecological at the same time.
Passive House is not a brand name, but a construction concept that can be applied by anyone and that has stood the test of practice.

Yet, a Passive House is more than just a low-energy building.


  • Passive House buildings allow for heating and cooling related energy savings of up to 90% compared with typical building stock and over 75% compared with average new builds. In terms of heating oil, Passive House buildings use less than 1.5 litres per square meter of living space per year – far less than typical low-energy buildings. Similar energy savings have been demonstrated in warm climates where buildings require more energy for cooling than for heating.

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  • Passive House buildings are also praised for their high level of comfort. They use energy sources inside the building such as the body heat from the residents or solar heat entering the building – making heating a lot easier.

  • Appropriate windows with good insulation and a building shell consisting of good insulated exterior walls, roof and floor slab keep the heat during winter in the house – and keep it out during summer.

  • A ventilation system consistently supplies fresh air making for superior air quality without causing any unpleasant draughts. This is e.g. a guarantee for low Radon levels and improves the health conditions. A highly efficient heat recovery unit allows for the heat contained in the exhaust air to be re-used.

Passive House
What is a Passive House?

Is it possible to achieve the Passive House standard if I am just building an extension or renovating my house?

It is not always possible to achieve the Passive House Standard (new constructions) for refurbishments of existing buildings, even with adequate funds. For this reason, the PHI (Passive House Institute) has developed the “EnerPHit – Quality-Approved Energy Retrofit with Passive House Components” Certificate.

Significant energy savings of between 75 and 90 % can be achieved even in existing buildings, for which the following measures have proved to be particularly effective:

  • improved thermal insulation (based on the principle: if it has to be done, do it right)

  • reduction of thermal bridges

  • considerably improved air-tightness

  • use of high quality windows (there is no reason why Passive-House-suitable windows should not be used whenever the opportunity arises)

  • ventilation with highly efficient heat recovery (again, Passive-House-suitable systems are very recommendable)

  • efficient heat generation

  • use of renewable energy sources

These are exactly the same measures that have proved to be successful in new constructions. A number of examples demonstrating the application of high-efficiency technology in existing buildings have become available in the meantime. 

For more information on the EnerPHit standard and how we can help you achieve this standard of refurbishment for your project, give us a call or fill in the online form in the Contact Us section of the website.

Is it possible to achieve the Passive House standard if I am just building an extension or renovating my house?
What happens if I can't afford to implement all the changes I want right now. How do I balance my low energy aspirations with my brief and my budget?

What happens if I can't afford to implement all the changes I want right now.  How do I balance my low energy aspirations with my brief and my budget?

All is not lost.  Currently, many retrofits are carried out as individual measures not taking into account further improvements to be implemented in the future, nor involving an architect. As a result, sustainability objectives are not achievable, any energy-saving potential is gone to waste, and unnecessary costs are generated. To change this, Passive House players are needed to create a long-term retrofit plan, in which the objectives are clearly defined together with the owner. For this, one can turn to the professionals with the relevant skills, for example, us as certified Passive House Designers.
To support this approach, the Passive House Institute offers the possibility to pre-certify the first step of an EnerPHit step-by-step retrofit. For this, it is necessary to submit an energy balance with the Passive House Planning Package PHPP 9 (2015) and a so-called EnerPHit Retrofit Plan. These should state that at least 20% of energy savings are achieved through the retrofitting steps. Therefore, independent quality assurance is also available in step-by-step retrofits. This is offered by all certified Passive House Designers.

If you are planning to extend or renovate your existing property anyway why would you not consider carrying out these works to the highest possible standards within your budget.  By not considering this we are in danger of locking in the building to a poorer standard of energy efficiency and making it more difficult to ever upgrade the building for the life cycle of the newly renovated building which could be 50 years or so.


We can prepare an EnerPHit Retrofit Plan (ERP) that works for you allowing the works to be properly phased.  The ERP stays with the building so even if you plan to move on in 5-10 years you will be passing on a building that can easily be upgraded by any new occupants which will add to the value of your house.  

I want to build a new Low Energy Home but I can't meet the Passive House Standards. Where do I start?

I want to build a new Low Energy Home but I can't meet the Passive House Standards.  Where do I start? 


A new standard referred to as the PHI Low Energy Building has been added to the PHI building criteria.  The requirements for this are slightly less stringent than those for a Passive House.  This standard is aimed at buildings with difficult prerequisites such as extremely small detached houses in strongly shaded situations.  Another application is for buildings which narrowly miss the Passive House standard on account of unplanned deviations in construction, e.g. air-tightness level not meeting the requirements.

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What is a NZEB and what are the implications for me?


A 'Nearly Zero Energy Building' is a building that has a very high energy performance rating and the nearly zero energy it takes to heat or cool the building should be provided to a significant extent by renewable energy sources, including energy produced from renewable sources nearby or on-site in the form of PV or solar thermal panels, air or ground source heat pumps, etc.




The NZEB standard will apply to all new buildings occupied after the 31st December 2020. For Public Sector bodies, the standard will apply to all new buildings owned and occupied by the 31st December 2018.

As with previous Building Regulations there are transitional arrangements in place where buildings are occupied after these dates but work commenced prior to 31st December 2018 for Non Domestic Buidlings and 31st October for Domestic Buildings.

For new dwellings

For all new builds, NZEB is equivalent to a 25% improvement in energy performance on the 2011 Building Regulations. A range of examples are shown in excel versions of the DEAP software available in the Domestic BER Resource page. Key changes to Part L for NZEB compliance include a Maximum Energy Performance Coefficient of 0.3, a Maximum Carbon Performance of 0.35 and a renewable Energy Ratio of 20%.

For major renovation to existing dwellings

For existing buildings, major renovation is typically activated under the following circumstances, where the work affects greater than 25% surface area of the existing dwelling:

  • External Wall Renovation, external or internal insulation

  • External Wall & Window Renovation

  • External Wall & Roof Renovation

  • External Wall & Floor Renovation

  • New Extension

The cost-optimal level is a primary energy performance of less than 125 kWh/m2/yr (B2 BER) when calculated using DEAP or upgrade of ceiling insulation and heating system.

Further details can be found on the Department of Housing, Planning and Local Government website.

If you are considering an extension or a new build house, give us a call and we can help you comply with the latest regulations.  



The UK has been a part of the Energy Performance of Buildings Directive (EPBD) that came into force in 2010 and it was designed to encourage the improvement of the energy efficiency of buildings, helping people to save money and energy with the overall aim of reducing carbon emissions. 


The UK has committed to an 80% reduction in carbon emissions when compared to 1990 levels by the year 2050.  To achieve this, the way we build new homes and upgrade existing homes must change and we must try to eradicate emissions from buildings completely if those targets are to be reached.  


The most challenging target of all for the UK is that all new buildings are required to be Nearly Zero Energy Buildings by 31st December 2020.  Given the result of the Brexit referendum, it is important to note that the EPBD is now part of UK legislation and will remain in place once the UK leaves the EU.


Currently, the UK's approach to carbon emissions does not align with the EPBD requirements for a NZEB which states the importance of renewable energy sources in meeting the energy demand.  This has not yet been outlined by the UK Government but the latest update to Part L & Part F of the Building Regulations and the introduction of SAP 10 should shed more light on the matter. 


This is all leading to the new Future Homes Standard which is due to be implemented in 2025 which plans for all new build homes to be off the gas grid, encourages the use of heat pumps, triple glazing and more stringent fabric efficiency standards for walls, floors and roofs.

If you are considering an extension or a new build house, give us a call and we can help you comply with the latest regulations.  

What is a NZEB and what are the implications for me?
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