n 1991, Wolfgang Feist and Bo Adamson applied the passive design approach to a house in Darmstadt, with the objective of developing a prototype low-energy home. The design proved successful, both in terms of energy consumption and comfort, and Passivhaus is now considered the ultimate in building performance. Passivhaus fundamentally requires a balance of three elements: energy, quality and cost – encompassing heating, cooling and thermal comfort which all have to be met cost-effectively.

Achieving the design performance as detailed in the build specification can present challenges – eliminating the gap between design and as-built performance is a key issue within the construction industry. Developers, architects and engineers are beginning to recognise the impact of building details and specification on energy performance and are keen to promote best practice.

Though renewable technology has its place, there is no doubt that the energy performance of the building’s external fabric is the most cost-effective, reliable and long-term, low-maintenance solution. This is what ‘fabric-first’ and Passivhaus principles are all about – high-performance insulation, good airtightness, the minimisation of thermal bridging and harvesting the sun’s energy through solar gain via south-facing windows. In essence, this means that the building does the work, rather than relying on occupiers operating and maintaining costly renewable energy devices.

Whilst the benefits of the fabric-first principles are well-documented, we still find some projects that only specify U-values whilst the SAP rating of a dwelling is driven by the interlinked properties of U-values, Psi values and airtightness. This is likely to be because U-values are readily calculated whilst the overall Y-value can only be determined once the building details are known and the individual junction Psi values input against actual junction length.

Passivhaus is a building standard that is truly energy-efficient, comfortable, ecological and, when the reduction in long-term operating costs are taken into consideration, affordable. It is a construction concept that follows a set of rigorous and certifiable principles that have stood the test of time and practice.

Sulgrave Gardens

Kingspan Timber Solutions are pushing the practical application of new technologies to create high-performance building envelopes. Prefabrication and lean design expertise is invaluable when dealing with the enhanced thermal and airtightness requirements of Passivhaus projects, such as the Greenhauses in Sulgrave Gardens.

Sulgrave Gardens is an award-winning scheme, which highlights the viability of Passivhaus dwellings as a sustainable solution in urban locations that might previously have been viewed as unsuitable. The striking brick finish and careful detailing, determines that eco-homes can be attractive, while offering energy-saving benefits. The landscaping unites the high-quality, yet low-maintenance buildings, and has been designed to encourage sociability and informal play. The attractive approach to the landscape is created with a pedestrian-priority shared surface.

The motivation behind the Sulgrave Gardens development was to make use of the most innovative methods of construction. The project focused on making sustainable living not just luxury homes for those who can afford it, but instead aimed to make Passivhaus more widely available to all.

Greenhauses represents a significant step forward in bringing Passivhaus into common use in the UK, in an affordable and deliverable format. Cartwright Pickard was appointed to design the Greenhauses in Sulgrave Gardens, which is London’s largest Passivhaus development. The project comprises a terrace of three-storey houses together with two five-storey apartment buildings, all of which have been constructed to Passivhaus principles. The development is completed with four mews houses with roof terraces. These homes have been fully Passivhaus certified and are not only designed to save residents a significant amount on energy bills – up to 90% in the case of the certified units – but also to provide considerably improved indoor air quality.

The innovative buildings source energy from body heat from residents within the building and solar contact, which is obtained from the triple glazed windows that are installed with high levels of insulation and minimal air leakage. The shell of the building, consisting of highly insulated exterior walls, roof and floor slabs, keep the warmth inside the house during cold months and outside in the summer months.

To complement the architecture in two adjacent conservation zones, brick was chosen as the primary facade material for the buildings. Given the tight urban nature of the site, minimising the thickness of the remaining wall build-ups was key, whilst still attaining the required level of thermal performance.

Each of the four blocks required a specific design response so as to meet the challenges of the planning and architectural context, and the energy use and heat loss targets of Passivhaus. Two main construction methods were used both utilising the high-performance Structural Insulated Panel system (SIPs). Kingspan TEK SIPs produced the primary structure of the 10 houses, with a concrete frame insulated with Kingspan TEK cladding panels being developed for the 20 apartments.

Both build-ups achieve outstanding thermal performance with final external wall U-values of 0.10 W/m2K. The proprietary jointing system featured on both Kingspan TEK products, in combination with the additional airtightness detailing on the project, ensured that air loss is below the 0.6 air changes per hour @ 50 Pa. To maintain a constant flow of fresh air, mechanical ventilation heat recovery (MVHR) systems were installed, using heat from the outgoing air to warm the incoming, fresh air. Building performance evaluation is currently underway together with occupier wellbeing research.

The Kingspan TEK Building System

The Kingspan TEK Structural Insulated Panel System is a Passivhaus Institute Certified Building System and has been installed into the Sulgrave Gardens project, offering a hybrid structural frame solution. The TEK Building System comprises 142 or 172mm thick structural insulated panels connected with a unique jointing system for walls and roofs.

The proprietary jointing system used with the Kingspan TEK Building System creates an incredibly airtight structure which can achieve 1.0m3/hr.m2 @ 50 Pa.

The Kingspan TEK Cladding Panel

The Sulgrave Gardens development uses the Kingspan TEK Cladding Panels, which is an innovative Structural Insulated Panel System – capable of cladding any structure – whether it is made of timber, steel or concrete. The panels are 142 or 172mm thick and consist of a high-performance rigid urethane insulation core, sandwiched between two layers of 15mm oriented strand board (OSB). Panels are manufactured to suit the individual project. Each panel has a standard dimension of width: 200mm (minimum), 1220mm (maximum) and length: 7500mm (maximum), but can be pre-assembled prior to delivery in our factory using TEK’s unique jointing system to suit efficient crane erection.

Opportunities for growth

The transition to low-carbon economy presents our industry with great opportunities for growth. Environmental considerations will transform how our buildings are constructed, what materials are used and the methods employed. We are now on the cusp of the predicted ‘sea-change’ and the time is right for the construction industry to embrace innovative timber technology and off-site techniques to develop better buildings at a rapid rate to enhance lives, minimise the environmental impact and reduce energy costs for occupants for many years to come.