Passive House principles

What is a Passive House? 

The Passive House (or Passivhaus, in Europe) standard is a building standard and construction concept designed to drastically increase the energy efficiency, comfort and longevity of a newly built property. Read our Guide to Passive House Requirements for technical details of Passive House certification.


What are Passive House windows? 

Passive house requirements are performance-based. To be suitable for use in a Passive house, windows must have a whole window U-value of 0.80W/(m²K) or less. They are usually triple-glazed, airtight, with insulated frames or thermal breaks and contain inert gas between the glass panes. 



Are Norrsken Windows Passive House Standard?

All of the windows and doors in our Passiv and Passiv+ ranges (300 and 400 series triple-glazed products) meet the performance criteria for Passive house projects. Our products are made from engineered timber, a natural insulator. They contain one or two panes of Low-Emissivity (Low-E) glass and argon gas between panes. Learn more about Low-E glass here.
View our Passive House Product directory here.



Do Passive Houses overheat in summer?

In a word: no. Passive houses are designed to be comfortable in both low and high temperature periods. Contrary to some expectations, high levels of insulation help to keep the indoor temperature low in buildings with adequate ventilation during the summer. 

This article explores the effects of window size, orientation, shading, thermal insulation and internal heat sources on overheating in a German case study passive house.



Overheating: Passive House design ensures a comfortable temperature throughout the year. This Oxfordshire home, which has no heating, is a perfect example. 

HOW DO PASSIVE HOUSES WORK?

Passive Houses achieve their high level of performance by meeting exacting criteria in five main areas of the building’s envelope:

  • thermal insulation;
  • energy efficient triple-glazed windows; 
  • effective ventilation; 
  • airtight construction; and 
  • elimination of thermal bridging and ‘cold spots’. 

Passive houses make use of existing energy sources, such as solar heat entering the building or the body heat of its inhabitants, to heat the building. Careful planning in the design and construction stages of the building ensures that the home is both very thermally efficient and provides an extremely comfortable living experience. 






CAN YOU OPEN THE WINDOWS IN A PASSIVE HOUSE?

Yes, you can open the windows in a Passive house to let fresh air in, just as in any other building. It will not compromise your efficiency. In fact, opening your windows is the simplest and cheapest way of cooling your home in summer.

The Passive House Institute recommends having "at least one window in each room openable and also have a tool to keep it fixed at a specific level [i.e. a Tilt & Turn Window]”. To learn more, read Six Reasons Why You Still Need Openable Windows on the Passipedia website.



WHY CHOOSE NORRSKEN WINDOWS FOR A PASSIVE HOUSE? 

We've identified five key reasons:
  • We're deeply passionate about energy efficiency, and our service reflects this commitment. 
  • Our superior products are designed for low energy and Passive house projects 
  • Our team has years of Passive House experience and expertise that goes beyond merely windows and doors
  • We're renowned for exceptional customer service
  • Our products are bespoke, and we know the importance of meeting a huge range of individual project requirements
Read more about Norrsken and Passive Houses here. 


How do Passive Houses work?

Passive Houses achieve their high level of performance by meeting exacting criteria in five main areas of the building’s envelope:

  • thermal insulation;
  • energy efficient triple-glazed windows; 
  • effective ventilation; 
  • airtight construction; and 
  • elimination of thermal bridging and ‘cold spots’. 

Passive houses make use of existing energy sources, such as solar heat entering the building or the body heat of its inhabitants, to heat the building. Careful planning in the design and construction stages of the building ensures that the home is both very thermally efficient and provides an extremely comfortable living experience. 






Can you open the windows in a passive house?

Yes, you can open the windows in a Passive house to let fresh air in, just as in any other building. It will not compromise your efficiency. In fact, opening your windows is the simplest and cheapest way of cooling your home in summer.

Passipedia recommends having "at least one window in each room openable and also have a tool to keep it fixed at a specific level [i.e. a Tilt & Turn Window]”. To learn more, read Six Reasons Why You Still Need Openable Windows on the Passipedia website.



Why Choose Norrsken Windows for a Passive House? 

We've identified five key reasons:
  • We're deeply passionate about energy efficiency, and our service reflects this commitment. 
  • Our superior products are designed for low energy and Passive house projects 
  • Our team has years of Passive House experience and expertise that goes beyond merely windows and doors
  • We're renowned for exceptional customer service
  • Our products are bespoke, and we know the importance of meeting a huge range of individual project requirements
Read more about Norrsken and Passive Houses here. 

The Benefits of Passive Houses

HOW DOES A PASSIVE HOUSE BENEFIT ITS OWNERS? 

Passive Houses provide many benefits to their owners, including:

  • Energy savings - You can expect meaningful energy savings because building to the Passive House standard materially reduces the energy usage of a home.
  • Lower heating costs - Lower energy usage means lower costs to heat and cool your home on an ongoing basis - no small boon in today’s uncertain and inflationary climate.
  • Affordability - Some Passive Houses use just 10% of the energy of a normal home. A Passive House will recoup the initial investment into its components and more over its life, making it not only an efficient but affordable building standard.
  • No performance gap - Rigorous planning and certification processes means that there is usually little to no performance gap. Energy savings predicted from a Passive build are real, not just on-paper figures.  
  • Durable buildings - no cold or damp spots means minimal condensation related damage, and a more durable building over time.
  • Comfort - "Energy efficiency is actually only part of passivhaus. People don’t often realise that the Passivhaus Standard is also a rigorous comfort standard”, says Passive House designer Elrond Burrell
  • A healthier living environment thanks to ventilation systems and condensation, cold spot and damp-eliminating design. 
  • Other financial benefits - Access to reduced tariffs, lower maintenance costs and higher potential for green mortgages, to name a few. 

ARE PASSIVE HOUSES ENVIRONMENTALLY FRIENDLY?

Yes. Says the Passipedia website: “Passive House buildings are eco-friendly by definition: They use extremely little primary energy... The additional energy required for their construction [embodied energy] is insignificant compared with the energy they save later on." 

The Passive House concept is a sharp deviation from the traditional carbon-heavy way we build, heat and run our homes. It represents an approach to building that is inherently geared towards sustainability - and is already making a material difference to the energy demand of new builds and retrofit projects across Europe and the UK. 


ARE PASSIVE HOUSES HEALTHY? 

Passive ventilation systems produce a consistent supply of fresh air throughout the building, meaning higher quality and more hygienic air supply. Fresh air and a condensation-free environment also reduces the risk of mould, damp and cold spots - healthier for the inhabitants, and more comfortable than in a typical home.


Where can I find UK Passive House Suppliers?

The Passivhaus Trust is a UK affiliate of the International Passive House Association (iPHA). The PHT promotes the adoption of Passivhaus in the UK. You can find a comprehensive list of Passivhaus Trust members and components suppliers for UK Passive House projects here. 

Glazing Design choices in Passive Houses

WHAT IS THE WINDOW-TO-WALL RATIO IN PASSIVE HOUSE?

Passive houses - in fact, all houses - must strike a balance in the proportion of glazing on any facade. 

Solar gain through glazing is a primary heat source for Passive Houses, but too much glass risks overheating. This is inefficient if a cooling system is then needed. Overhangs such as balconies or roofs can usefully mitigate overheating in certain circumstances, but glass-box-like homes are generally avoided in Passive House design.

There is a second factor influencing glazing apertures. Glass production is a carbon-intensive procedure relative to other Passive House components. Worldwide, glass production releases more than 86 million tonnes of CO2 annually. Natural gas is used to heat raw materials to about 1500°C, accounting for 75-85% of CO2 emissions in the process. Read more about mitigating overheating here. 


HOW DOES WINDOW SIZE AFFECT INTERNAL TEMPERATURE IN A PASSIVE HOUSE?

We know that the more glass there is in a south-facing building, the more solar gain experience. When glazing makes up a suitably small proportion of a building’s facade, solar gain is too low to make a significant positive impact on the heating demand. 

A central European case study found that, when glazed areas constitute less than 14% of the facade, a Passive House does not exceed internal temperatures of 25 degrees even in summer. So there was no overheating, but the specific heating demand actually fell short of passive house requirements. 


Mitigating solar load: overhangs, such as balconies, can prevent overheating in Passive Houses like this Devon apartment block. 

The more glass used in a home, the higher the embodied carbon. Reducing embodied carbon is as critical in the long term as lowering building energy demand. Some recent studies even argue that highly efficient double glazing should be used over triple glazing for this reason.

Passive house design takes these factors into consideration. Use the PHPP and / or a Passive House designer or consultant to navigate these factors in your own Passive House design.


HOW MUCH GLAZING CAN I HAVE BEFORE OVERHEATING STARTS TO OCCUR? 

A south-facing home with approximately 30% glazing in the south-facing facade (triple-glazed, low-E coated units) experiences a noticeably higher frequency of internal temperatures over 25 degrees. However, even in summer and without temporary sunshades, excess overheating did not often occur - that is, >10% of occupied hours at 25 degrees or more. (Source: Passipedia)


AND HOW MUCH GLASS IS TOO MUCH?

In a south-facing home where triple glazing and Low-E glass make up over approximately 42% of the facade unacceptable overheating occurs. The home was often (at least 10% of occupied time) at an internal temperature over 25 degrees, and temporary sun shades had to be used throughout summer periods to lower the solar load through the glass.

Overheating usually occurs because the solar loads through the glass are too high. This can be avoided with professional planning and the use of temporary shades, blinds or other relatively simple solutions, or simply through planning fewer windows in the building’s design. Read more about mitigating overheating here. 

Costs of Passive Houses

ARE PASSIVE HOUSES EXPENSIVE?

It is generally (but not always) true that Passive House construction costs more in components than a standard build. 

Research by the Passivhaus Trust in 2019 found that, “compared with standard construction, building to the Passivhaus standard incurred an extra cost of approximately 8%, forecast to reduce to 4% at scale and over time.” 

A study by AECOM found an even smaller uplift - the capital costs of new builds reimagined as Passive Houses were estimated to increase by less than 1%. 


WHERE CAN I EXPECT AN UPLIFT IN COST? 

MVHR, wall & roof components (insulation) are the largest extra-over costs to build a Passive House on average. That said, there are notable offsets: heating systems in Passive Houses actually tend to cost less than typical builds. Passive building heating demand is capped at 15kWh/m2 per year - that’s 80-90% less than the average existing domestic building. Little wonder that smaller, less expensive heating systems are required. 

IS IT POSSIBLE TO BUILD A PASSIVE HOUSE AT NO EXTRA COST?

Yes. The Passivhaus Trust notes that ‘simple yet impactful early design decisions including building form, orientation & window design can drive efficiency. By offsetting these design savings against the extra costs for the higher quality fabric, it is possible to deliver higher quality Passivhaus buildings at no extra cost.’

Will this always be delivered in practice? Maybe not - cost uplift is clearly dependent on rigorous planning and attention to design details from early on in the passive House journey. 

To summarise: 
  • the capital uplift in Passive House building is not as significant as often assumed (1-8% rather than 10-15%). 
  • It is possible to build to the standard at very little or no extra cost. 
  • If you design well, you can offset the extra costs of high performance fabric and components.

Viewed in terms of whole-life performance, financial savings by Passive Houses over their lifetime usually outweigh the initial investments into their components by a significant margin.

Useful Links & Resources

A non-exhaustive list of useful resources to help you on your Passive House journey. 

Read our Guide to Passive House Requirements to learn more about technical and performance requirements for "the world's leading standard in energy efficient design".

The Passive House Institute is the global centre of Passive House research and certification. The site contains a wealth of information and guidance. You can download a leaflet from the Passive House Institute on technical specification for Passive House certification here.

Passipedia - The Passive House Institute's primary technical knowledge bank for research, technical information and more.

The Passivhaus Trust is the leading organisation promoting the adoption of Passive House in the UK. It is part of the International Passive House Association (iPHA). You can find UK manufacturers and systems suppliers for your Passive House project and more useful tips and information. In particular, the Benefits of Passive Houses brochure usefully categorises and then explores 6 different ways passive Houses benefit their owners and society.

The Passivhaus Trust: the Performance Gap in UK Passivhaus Whitepaper This paper provides statistical analysis of the significance of Passivhaus performance gap compared to ‘standard’ build performance gap. Evidence shows that Passive Houses do not deliver significantly below their predicted performance - on average, in fact, the buildings assessed performed better than predicted. 

The PH Ribbon is a custom toolbar (ribbon) in Excel specifically written for PHPP calculations as an add-on and aid.

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