Stephen Edwards| Catalyst Housing
Stephen Edwards sustainability manager of Catalyst Housing summarises a recent Green Register site visit.
Catalyst are one of the UK’s leading housing associations and Green Register members. They are a member of the G15 group and provide a wide range of affordable housing with over 21,000 homes in London and the South East. In May 2018, Catalyst Housing’s Sustainability Team invited colleagues from the Property and Growth Directorate to attend a Green Register site visit to a Norwich City Council building site to find out how the local authority are introducing Passivhaus principles into one of their new social housing schemes.
The 105 home site is in Goldsmith Street and consists of 45 houses and 60 flats. The site is set to be the largest 100% certified Passivhaus social housing scheme in the UK.
Passivhaus is a system of designing buildings that dramatically reduces energy use through high standards of fabric efficiency. It was developed in Germany over 25 years ago and is now gaining popularity in the UK as an effective approach to reducing carbon emissions and fuel poverty and providing high standards of comfort and building health.
Associate James Turner and Project Architect Henry Wootton of Architects Mikhail Riches, with the client Andrew Turnbull of Norwich City Council and Geoff Hales Contracts Manager for the main contractor RG Carter jointly presented a talk providing the background of the site’s development and outlining some of the design details and specifications. This followed a walk through the site to see different stages of progress of the development. The walls for this development are particularly thick at 600mm with an internal timber frame (constructed offsite) filled with Warmcel fibre insulation (made from recycled newspaper) and the overall fabric of the building has been designed to achieve very high levels of airtightness. Fresh air is provided with Heat Recovery Ventilation which captures the heat from the stale air before it is expelled, thereby minimising any unwanted cooling from the system. The buildings are also designed to maximise solar heating in the winter and minimise solar heating in the summer.
Passivhaus buildings typically save up to 80% of the energy used for heating, meaning residents will have very low energy bills and only two radiators were required to be installed for each property.
Norwich City Council used a traditional contract framework and this enables the architects to have input and oversite throughout the delivery. A Passivhaus consultant is being used and a performance related contract ensures the main contractors deliver the level of quality needed to meet the Passivhaus accreditation requirements.
There was very positive feedback from colleagues who attended this site visit with 90% finding it either very or extremely useful. Colleagues also indicated that both their knowledge of Passivhaus and their confidence in working on a Passivhaus scheme significantly increased (from an average of 4/10 to 7/10 in both cases).
The three most important benefits colleagues thought Passivhaus provides are:
1. Low energy consumption
2. Reducing fuel poverty
3. Reducing long term maintenance costs
So should Catalyst be building to Passivhaus standard? Overall there was a very positive sense from colleagues on this question, with 80% saying they thought Catalyst should be building Passivhaus on either some or most of our new build properties. However, 20% were more cautious feeling that Catalyst was not yet ready to build Passivhaus.
Here were comments made by colleagues:
“… as a business we should take the first opportunity to try to build some Passivhaus homes. These should be out of London where we may be able to find better labour resources and where the land is cheaper allowing for more room between plots to help manage solar gain.”
“I was impressed by the fact that the scheme is meant for social rent, which means that the public sector can definitely achieve very high standards in planning and construction.”
“Passivhaus appears to be getting more and more achievable for social landlords and the long-term benefits of high performance, reduced energy bills and low maintenance costs far outweigh any small increase in capital costs.”
“Very interesting concept but I am not confident that Catalyst are in a position to proceed down this route given the additional costs involved and our current financial hurdles.”
Colleagues were quick to identify key challenges that would face Catalyst in undertaking Passivhaus projects:
• planning in higher capital costs
• finding competent and Passivhaus-experienced contractors
• the importance of the relationship between architect, client and developer
• ensuring accurate and detailed design and modelling early in the development phase
• the need to use high quality materials and new specialist products
• the importance of quality control through regular checks and testing throughout the construction process to ensure the performance quality has been reached at all the different levels and stages
• understanding the risk of not achieving certification, especially if this is critical for planning or funding requirements
• how to support residents in making the behavioural adjustments to living in a Passivhaus
However, the many benefits of building Passivhaus homes are clearly providing a strong business case and would help us:
• meet both current and future planning and legal requirements for zero and low carbon buildings
• reduce Zero Carbon tax payments on London schemes
• improve the quality and building performance of our properties
• reduce defects and long-term maintenance costs
• significantly reduce energy bills - which also impacts on reducing rent arrears
Globally there are now 65,000 Passivhaus accredited buildings. Here in the UK there is an upsurge of interest in Passivhaus and with social landlords such as Norwich City Council, Hastoe Housing Association and Exeter City Council leading the way in adopting a Passivhaus approach, the time for Catalyst to dip our toe in the water has surely come.
For more information about Passivhaus visit: http://www.passivhaustrust.org.uk/