This is a Passivhaus Basics blog post that gives an overview of a specific aspect of the Passivhaus Standard.

The international Passivhaus Standard does not explicitly require mechanical ventilation. And yet almost every certified Passivhaus building includes a mechanical ventilation system with heat recovery.

What is mechanical ventilation with heat recovery (MVHR) and why is it needed in Passivhaus buildings?

Mechanical ventilation is familiar to most people. This leads to the assumption that a Passivhaus ventilation system is the same as other mechanical ventilation systems. It is not.

There are things that MVHR does not do. It is important to know what these are in order to understand the difference between Passivhaus MVHR and other types of ventilation.

And there are things that Passivhaus MVHR does do that other ventilation systems don’t, including ‘natural ventilation’. It is important to know what MVHR does do, as MVHR is vital to the consistent success of the passivhaus standard.

Mechanical ventilation with heat recovery (MVHR) is key to delivering the benefits the Passivhaus Standard promises – radical energy efficiency and exceptional comfort.

036 What is Mechanical Ventilation with Heat Recovery (MVHR)?
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This is a Passivhaus Basics blog post that gives an overview of a specific aspect of the Passivhaus Standard.

Thermal bridges (sometimes referred to as “cold bridges”) in the building envelope have a measurable impact on energy efficiency and thermal comfort. The impact can be relatively low on buildings that are not very well insulated. However, with buildings that are well insulated and energy efficient, the relative impact of thermal bridging is significant.

Building regulations and codes are now starting to recognise this and in some places, it is required or recommended that thermal bridging be minimised.

The Passivhaus Standard recognises the importance of thermal bridges and the significant impact they can have on the high-performance Passivhaus building envelope. The Passivhaus Standard requires a continuous thermal envelope: this means thermal bridge free construction.

This blog post answers the following questions:

  • What is a thermal bridge?
  • What are the different types of thermal bridges?
  • Why are thermal bridges a problem?
  • What is thermal bridge free construction?

The Passivhaus Standard requires thermal bridge free construction to ensure a robust high-quality building envelope that delivers radical energy efficiency and exceptional comfort.

What is Thermal Bridge Free Construction
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This is a Passivhaus Basics blog post that gives an overview of a specific aspect of the Passivhaus Standard.

The Passivhaus Standard requires airtight construction. What does this mean?

Essentially it means a draught-free building envelope.

A clear airtightness strategy is required to achieve this. The airtight line needs to be continuous even when formed of different materials. And it needs to be joined up, even where there are penetrations.

Sometimes airtight construction gets confused with how a building is ventilated or with ‘breathing construction.’ This post clears up these particular confusions.

And why does the Passivhaus Standard require airtight construction?

Airtight construction is draught-free construction. It is an essential part of the Passivhaus Standard to protect the building envelope, to ensure radical energy efficiency and to provide exceptional comfort.

030 What is Airtight Construction
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A passivhaus home in almost all climates across the world will include a mechanical ventilation system with heat recovery (MVHR*). This kind of ventilation system is required for both energy efficiency and for comfort. However, to many people this is an intimidating and misunderstood aspect of passivhaus. As a result, there are various concerns and misconceptions about what a passivhaus ventilation system is and how you use it.

To address some of these issues I have enlisted the help of Zehnder, a global supplier of Passivhaus Certified ventilation systems. In this post, we explore the following aspects of a residential passivhaus ventilation system:

  1. How do I control the ventilation system?
  2. What day-to-day interaction do I need to have with the ventilation system?
  3. What is the boost function and when should I use it?
  4. When should I switch the ventilation system off?

Rupert Kazlauciunas, Senior Technical Advisor at Zehnder Group UK, very kindly provided answers to my questions

In a residential passivhaus, the ventilation system can be simple to use. It will save energy and money, while ensuring comfort and excellent indoor air quality.

029 Residential Passivhaus Ventilation System
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This is a Passivhaus Basics blog post that gives an overview of a specific aspect of the Passivhaus Standard.

In passivhaus design and construction, there are frequent references to the “building envelope” and the “thermal envelope.” Neither are exclusive to the Passivhaus Standard, but both are important aspects of the standard.

A building envelope is the physical separators between the conditioned and unconditioned environment of a building including the resistance to air, water, heat, light, and noise transfer. The three basic elements of a building envelope area weather barrier, air barrier, and thermal barrier. [Wikipedia]

In simple terms, this means that the building envelope is made up of the walls, floors, roofs (or ceilings), windows and doors that separate the inside from the outside. The passivhaus building envelope is also made up of these elements, but there are some key aspects that make the passivhaus building envelope distinct.

The passivhaus building envelope requires a high-performance thermal envelope, it must be continuous and it is key to the fabric first approach.

028 What is the Passivhaus Building Envelope
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