Framing the industry to meet legislation

// the building envelope

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Housing associations constructing new timber frame houses have to consider intricate elements of the building process including product quality, performance and environmental soundness when specifiying materials. George Watson Product Manager at Coillte Panel Products looks at the continuing research and development into new timber panel products and asses how important it is for Registered Providers to consider the full spectrum of products available to them to help meet certain regulations or standards before building work commences.

Within the construction industry, timber is regarded as one of the most flexible, structurally sound and aesthetically pleasing building materials with one of the lowest carbon footprints, especially when compared to other building materials such as steel or brick and block. As such, timber is often used when housing associations employ a ‘fabric first’ method and can help achieve a low-carbon, high-performance energy efficient building envelope. The timber industry is growing due to a response in the need for building materials that match, and exceed, certain environmental standards.

As a unique market, the demand for Passive House and Zero Carbon homes has grown. Breathable panels with high vapour permeability are an ideal choice for the outer layer in “diffusion open” wall and roofing applications. As such, Coillte Panel Products introduced a structural, vapour permeable panel, Medite Vent, to its range of products, which is ideally suited to the needs of the timber frame and off-site construction methods. This kind of innovation in MDF suits the need for a breathable panel for use in external sheathing for all types of timber frame construction, supporting a well-ventilated building design.

With Medite Vent in particular, the independently tested low water vapour diffusion factor helps prevent condensation by allowing the passage of water vapour through the panel. Its high performance racking strength, in excess of Category 1 requirements, offers reliability and structural integrity.

Used correctly, external, breathable timber panels provide exceptional performance for any Fabric First building envelope approach and with further changes to Part L of the Building Regulations on the horizon, in the UK’s roadmap to zero carbon by 2016, UK buildings are only set to become more airtight. In this scenario there will be a greater need for a ‘Fabric First’ approach to the building envelope, to ensure the requirements of Part L for energy conservation and Part F for ventilation are balanced and met. This presents a further opportunity for Registered Providers to optimise on the potential for using structural, vapour permeable panels to help meet the desired performance criteria of their new homes, while also blending the installer friendliness of the products with environmental benefits that come with using timber frames over other materials.
The desire to meet Passive House standards in the UK has grown significantly in recent years and OSB panels in particular can play a big part in designing passive house structures. The standards for passive house state that units have to meet strict airtightness levels with a maximum air change rate of 0.6 air changes per hour at 50Pa of pressure.

To aid builders and specifiers to meet the Passive House standards and Part L of the Building Regulations, Coillte Panel Products collaborated with a leading institution of building physics to validate the air barrier properties of an OSB panel to create a new product called SmartPly VapAirTight.

The company developed a specialist surfacing technology for the product to ensure a high vapour diffusion factor, eliminating the need for additional air and vapour control layer (AVCL) membranes.  The rigid panel is less susceptible to on-site damage than flexible membranes and can be easily installed using standard woodworking methods. The smooth surface also provides an excellent substrate for the application of airtight tape at the panel joints.

Maintaining airtightness is extremely important when building domestic dwellings and this kind of innovation will further enable the construction of highly energy efficient homes and properties, ensuring housing associations and housebuilders can meet Passive House standards, should they desire, and ultimately to help the UK to meet European Union carbon emission targets.

The UK consumed a massive £1.15 billion of timber and panel products in 2013 , with sustainability rapidly becoming more of an issue over the years. The high consumption of wood is due to the properties that the material possesses. Using wood as an alternative to steel and concrete as a building material saves, on average, 0.9 tonnes of CO2 per cubic metre  whilst being durable, versatile and cost-effective. Today’s timber panels can be used in a range of applications including roofing, flooring and sheathing in timber frame construction with engineered panels providing further benefits of dependable performance with no knots or core voids to contend with.

As a material that is now recognised for its innovation, the use of timber frames in new-build homes has grown from 2% in the 1980’s to 27% in 2014 . Wood panels are becoming more and more innovative, and technological modifications such as these are used to make a specialist range of materials that create products with specific properties, such as durability, airtightness or even weather resistance.

However, tropical plywood imports that have no documentation, proof of legality and low levels of quality have for years threatened the environmental reliability of timber panels. Recent updates in legislation should see this threat removed from the market. Reputable manufacturers in the UK and Ireland are providing alternative products that are produced from raw materials sourced locally from sustainable, well managed forests to deliver superior integrity, reliability, performance and strength in timber frames.

In Autumn 2014, the FSC released statistics showing that 83% of timber in the UK comes from certified sustainable sources , such as Coillte’s. Crucially, as timber becomes recognised as a more desirable, durable and innovative product and the use of wood panels continues to increase, it is up to Registered Providers and contractors alike to ensure that when they are building timber frame homes, they are not only using products which help meet Passive House standards and UK Building Regulations but also that they are using certified wood panels to help completely eliminate the use of illegally sourced wood in the UK.

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