A house built using polyurethane materials consumes 85% less energy than a home built from conventional materials. They can provide very high levels of insulation with minimal thickness which in turn allows architects and designers to maximise the use of interior spaces. It is perhaps no surprise then that when it came to the construction of a passive house in Belgium, polyurethane insulation materials were used to create a highly insulating building fabric. Three years on, has the Polyurethanes Passive House in Brussels and its very well insulated and sealed envelope provided a comfortable and healthy environment throughout the year?

The end-of-terrace four-storey family house developed by ISOPA, the European trade body for diisocyanate and polyol producers, was completed in Evere near Brussels in 2013. It is now occupied and working as a low energy test bed, its running costs and energy use closely measured to show the savings possible for homeowners.

While there are over 12,000 new build Passive House certified buildings across Europe, the ISOPA house is unusual in using a high proportion of PU to achieve its highly insulating fabric first design which reduces the need for heating and saves around 80% of the energy used by a normal house. PU insulation has been used wherever possible from wall cavities to the floor, and windows to the roof.

The house has been designed so that all of the construction elements work together in an integrated way, from the solar panels on the roof to the geothermal heat pump and MVHR system which ensures that warm fresh air circulates internally despite the high air tightness levels. The University of Leuven has been evaluating the home’s overall performance, energy use and indoor comfort levels which would verify whether the PU products as installed were really achieving the calculated performance levels.

The analysis of the data yielded an estimated heat loss coefficient of 60.0 W/K, with a standard deviation of 3.0 W/K. This indicates that the thermal performance of the building fabric meets the very high standards expected, which was instrumental to the project reaching the performance levels required for Passive House certification.

Known for the comfort they provide, polyurethanes are ideal for Passive House construction because they provide very high levels of insulation thanks to low thermal conductivity, meaning they provide reduced thickness increasing their affordability and reducing the impact on building footprints. As well as requiring fewer adjustments to be made to the design of buildings and less aesthetic compromises such as with deep window reveals, further cost savings on depth of eaves, joists, rafters or studs, lengths of fixings can be achieved. In short, the extremely low U-values required for Passive House projects can be much more easily achieved with PU than with other materials as far fewer changes to design detailing are required.

Rigid PIR insulation boards are also light but strong, moisture-resistant and easy to install, and they, as well as spray foam PUR insulation, retain their insulating properties for the life of the building. Last but not least, PU materials contribute to preservation of natural resources by reducing the need for energy which assists their sustainability credentials in Passive House projects.

With a daunting 80% reduction in carbon emissions on 1990 levels called for globally by 2050, such efforts to create practical ‘near zero energy’ houses are essential. With houses accounting for 40% of energy consumed across Europe, achieving the means of constructing new Passive Houses affordably using PU which can deliver the results while saving homeowners money is the realistic way forward, as demonstrated at the Polyurethanes Passive House.

by Marleen Baes, BRUFMA Technical Committee Member

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SPI are one of the leading manufacturers of expanded polystyrene in the UK, supplying an extensive range of building and civil engineering products. With state of the art moulding and cutting machinery SPI can offer a wide range of grades and bespoke products to suit all types of projects.

As an insulation supplier SPI have seen trends in correlation with the increasingly demanding building regulations of part L conservation of fuel and power. Even after the scrapping of the 2016 zero carbonpolicy there is still a requirement to meet the 80% reduction in carbon emissions by 2050 under the Climate Change Act. There has been a call for innovative solutions when it comes to insulating the UK housing stock, the development of building systems which produce lower target U-Values has allowed for off-site construction to bloom, with a growth of products like SIPs, ICF walls and modular floors.

Recently this has lead to an increase in passive house foundation construction largely developed as offsite modular concepts, which allows for less installation time on site meaning the structure above can be installed earlier. Typically the foundations and structure can be completed within a week for a 4 to 5 bedroom house. Passive house foundations consist of a basic L shaped perimeter with standard boards up to three layers thick. Specialist clips are used to hold the whole foundation system together. The complete foundation base is then covered with a DPM and the structural concrete can then be poured.

Once the concrete is cured the superstructure can begin. Most commonly we have seen these foundations used with SIPs and lightweight timber frameworks. As an insulation provider the off-site development means we can cut bespoke products required by the layout of the build quickly and easily, making the whole process from conception to completion exceptionally fast.

These types of building elements and forward thinking innovations offer a certainty that builds can easily exceed regulations which when coupled with the environmental sustainability expressions of modern future proof housing make the prospects of a carbon neutral 2050 attainable.

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SmartPly is set to revolutionise the way timber frame structures are designed and built with its latest technological innovation – the SmartPly VapAirTight structural OSB panel. With integrated vapour control properties and airtightness engineered into each panel, SmartPly VapAirTight has performed six times better than PassivHaus standard for air leakage, making it the ideal panel system for ultra-low energy buildings.

The result of three years of rigorous development by SmartPly and extensive testing at the Fraunhofer Institute for Building Physics, SmartPly VapAirTight is recommended by the Passive House Institute as a product for providing airtightness. Each panel features alternating layers of wood strands coated with a high quality formaldehyde-free resin and wax to deliver outstanding levels of airtightness. A specialist coating is then applied to add vapour resistance and provide a premium performance OSB solution for super-insulated and passive buildings.

“OSB is assumed to be airtight, but tests prove a huge variation in performance, between manufacturers and even between different production cycles,” explains David Murray, Innovation Manager at SmartPly. “Developed from our OSB3 system, SmartPly VapAirTight has integrated vapour control and unrivalled air barrier properties and will help to close the gap between design and as-built performance.”

Available in a standard 2397mm x 1197mm size, the panel uses a newly developed high performance coating to ensure consistently high vapour resistance across its entire surface. The smooth and durable surface has also been developed to provide superior bonding of airtight tape at panel joints. Where air and vapour control layer (AVCL) membranes are notoriously difficult to seal, SmartPly VapAirTight offers excellent seal adherence to prevent air leaks, condensation and structural damage.

Manufactured from FSC-certified timber to the specification detailed in BS EN 300:2006, the rigid panel is a sustainable, robust and cost-effective alternative to specialist AVCL membranes. With minimal risk of damage during assembly, transport and installation, airtightness should not be compromised thereby ensuring the panel performs as well on the construction site as in factory controlled conditions.

By the very nature of the product, SmartPly VapAirTight can also reduce waste and man hours, as site applied, or factory applied, air and vapour control layers are not required. The panels can be readily cut and fixed using standard timber frame fixings, removing the need for additional membranes, sealants and foams.

Suitable for both new build and renovation projects, SmartPly VapAirTight is a versatile, strong and cost-effective OSB panel system. If the UK is to meet its target of an 80% cut in carbon emissions by 2050 with all new homes built to be ‘zero carbon’, SmartPly’s latest innovation could play a vital role as part of a highly sustainable and fabric first approach.

For more information on the new SmartPly VapAirTight panel system, go to