Sarah Lewis, a sustainability architect specialising in Passivhaus, inspecting one of her project sites.

Buildings have a huge impact on the environment and on people's quality of life but, once in use, they often fail to achieve the level of energy efficiency they were designed to. The end result is buildings that aren’t comfortable to live or work in, higher energy bills and higher CO2 emissions. Passivhaus buildings use passive design techniques and controlled ventilation to reliably achieve significant energy savings whilst providing high levels of comfort and indoor air quality. 

The Passivhaus Trust is the key organisation in the UK promoting the Passivhaus standard, supporting certification and providing quality control, training and advice to architects, engineers, suppliers and builders across the UK, as well as an annual conference and awards competition.


The Passivhaus Trust’s approach is one of rigour and quality assurance, upholding the Passivhaus standard in the UK by working in partnership with its network. By acting as a bridge to a globally recognised international standard, the Trust is both changing mindsets and enabling the building community when it comes to sustainable building practices.

2017 Ashden Award judging panel

Context

To maintain a healthy indoor environment, homes need to be kept at a comfortable temperature and properly ventilated, but this needs to be done in a way that conserves energy and limits CO2 emissions. Building regulations require new homes to be designed to use less energy than in the past but in practice there is a ‘performance gap’ and, once the home is in use, energy consumption is often higher than expected and comfort is compromised.

UEA ADAPT building - straw thatch wall and solar shading

The Passivhaus Trust

The Passivhaus Trust (PHT) is an independent, non-profit organisation that exists to promote the principles of Passivhaus design as an effective way of reducing energy use while providing high standards of comfort. It aims to preserve the integrity of Passivhaus standards and methodology, promote Passivhaus principles to industry and government, and to undertake research and development on Passivhaus standards in the UK. These aims are delivered through training for architects, engineers, builders and clients; masterclasses, seminars, conferences and other learning events; technical guidance notes and an online knowledge base; research, including monitoring and evaluation of Passivhaus buildings; and marketing, open days, an awards competition and other promotional events.

The PHT was founded in 2009, the same year that the first Passivhaus building was built in the UK, and since then has supported the industry in completing over 100 Passivhaus projects, resulting in over 500 certified units, most of which are homes. Other projects currently underway are expected to increase the number of completed units to over 1,000 by the end of 2017. 

Although meeting Passivhaus standards often costs a few percent more than average build costs, several housing associations in the UK have been using the standard in their new housing, because of the benefits it brings to their tenants, and the PHT has been instrumental in them adopting it.

A new Passivhaus site in London

The Passivhaus standard

Passivhaus, developed in Germany in 1989, is a building standard and methodology that, when rigorously applied, results in homes that require very little energy to be used for heating or cooling. This is achieved through very high levels of insulation, extremely high performance windows with insulated frames, airtightness, avoidance of ‘thermal bridges’ and mechanical ventilation systems with heat recovery. 

Homes and other buildings using Passivhaus techniques are designed carefully using the Passive House Planning Package (PHPP) software. To be certified as Passivhaus, a new building must use no more than 15 kWh/m2 per year for heating or cooling, and must have airtightness equivalent to no more than 0.6 air changes per hour at a pressure of 50 Pa.

Passive design

A core part of the Passivhaus standard is passive design, which maximises use of daylight for lighting, solar gain for heating in the winter, shading to reduce solar gain in the summer, and ventilation to provide summer cooling. By combining these techniques with good insulation and airtightness, most homes can be heated for much of the year by a combination of sunlight, waste heat from electrical appliances and the body heat of occupants. 

Ventilation in colder months is provided mechanically, but with a heat recovery system to capture heat from the outgoing air and use it to warm the incoming air. In warmer months, vents and windows can be opened to provide a natural flow of air through the building, or the mechanical ventilation system can be used with the heat recovery in bypass mode.

Smart features in a Passivhaus building

Costs and benefits of Passivhaus homes

Early Passivhaus projects in the UK saw building costs relative to typical new build uplifted by 15-20%, but some recent projects involving larger developments have seen the uplift reduced to between 0% and 5%. Passivhaus homes can see energy bills reduced by £500 to £1,000 per year, depending on the size of the home. The result is that households in Passivhaus homes are less likely to be in fuel poverty, because their energy bills are so low, despite the homes being at a comfortable temperature. 

There is anecdotal evidence from social landlords that rent arrears are significantly reduced in Passivhaus homes, and the Passivhaus Trust is seeking further evidence from landlords to back this claim up. There is emerging evidence that health benefits also result from Passivhaus homes, thought to be because the controlled ventilation avoids excessive humidity and high indoor CO2 levels, and the use of filters on the ventilation systems reduces the presence of pollen and particulates within the homes.

Without the Passivhaus Trust, these homes would not be here.

John Lefever, Regional Head of Development, Hastoe Homes​

Education, training and guidance

Providing training to support the industry is a core focus for the PHT. The range offered includes entry-level courses covering introductory material and good practice tips for Passivhaus beginners, as well as ‘Masterclass’ courses addressing advanced issues in depth for experienced practitioners, often using experts from amongst the PHT membership as tutors. 

An annual conference and additional seminars provide opportunities for larger audiences to hear from Passivhaus experts and network with others working in the sector. In addition to events, the PHT makes information available on its website in the form of technical guidance documents, knowledge bases and links to further sources of information and advice.

Promotion of Passivhaus

The PHT plays an important role in raising awareness of the Passivhaus standard, and in providing opportunities for potential users to learn more about it, see what it means in practice, and meet organisations that can help them with design and construction. In addition to conferences and other events open to the public, the PHT also makes presentations at trade shows and other events, and organises the UK section of the annual global Passivhaus open day, when Passivhaus homes and other buildings around the country are open for people to visit, to see for themselves what they are like. 

The PHT is currently running two promotional campaigns, one aimed at local authorities and housing associations, the other aimed at people planning to build their own home. In each case, the goal is to raise awareness of the benefits of Passivhaus design and appeal to an interest in long-term benefits, which may currently be less important to commercial developers.

One of the Passivhaus homes open to the public

The future

The potential for Passivhaus to be adopted more widely in the UK is significant, but depends to some extent on the demand for low or zero carbon homes. Although the UK government has dropped plans for a requirement for new homes to be zero carbon, London’s Mayor made use of his powers to require new homes planned in the city from October 2016 to be zero carbon, and other mayoral cities could adopt similar policies. Another source of demand for Passivhaus is long-term thinking by social landlords, putting priority on lower energy costs for their tenants, and there is already evidence of this happening.