Breathing space

Within the construction industry, timber has long been regarded as one of the most flexible, structurally sound and aesthetically pleasing building materials with one of the lowest carbon footprints. As such, wood panels are increasingly used by architects, developers and contractors looking to employ a ‘fabric first’ method to achieve a low-carbon, high-performance, energy efficient building envelope.

However, when designing and building timber frame structures, the risk of interstitial condensation is a key consideration as it can lead to mould growth, health issues for occupants and can even compromise structural integrity. Particularly as we try to increase our buildings’ airtightness, thermal performance and indoor air quality, breathability has become a critical issue affecting all areas of both new and retrofit buildings. Breathable panels with high vapour permeability are an ideal choice for the outer layer in ‘diffusion open’ systems, as they provide improved drying potential, minimise the risk of condensation and can help ensure the long term health of the building fabric.

Breath-taking qualities
Suited to timber frame and off-site construction methods, Medite Vent from Coillte meets the need for a breathable panel that can be used in external sheathing for all types of timber frame construction, supporting a well-ventilated building design.

Medite Vent combines high racking strength in excess of Category 1 requirements with excellent vapour permeability and high weather resistance – making it an excellent choice for the outer layer in ‘diffusion open’ systems. Independently tested by Fraunhofer Institute for Building Physics, the panel achieves a μ-Value (water vapour diffusion resistance factor) of 9.7 to help prevent condensation by allowing the passage of water vapour and excess moisture away from the indoor environment through the panel.

When constructing timber frame buildings to meet Part L and Part F of the building regulations, as well as Passivhaus standard, the external sheathing panel must also meet certain standards for racking strength. Suitable for use in humid conditions, Medite Vent is classified as structural and can be used in all types of timber frame as external racking and sheathing under Eurocode 5 EN 1995-1-1.

With a high racking strength in excess of Category 1 requirements, Medite Vent is designed to be reliable and offer structural integrity. Fixed in the same way as other timber sheathing materials with nails, staples or woodscrews, a typical wall build up will include an inner lining, timber batten to provide a service void, vapour control layer, timber stud with insulation infill, Medite Vent panel, waterproof membrane, ventilated and drained cavity, and a rainscreen cladding system.

Sustainability is also now a prerequisite for all projects and the environmental performance of the raw material is also a key consideration. Manufactured from FSC timber from the company’s own forests, Medite Vent is also produced using zero-added formaldehyde and carries the CE mark in accordance with EN 13986.

A textbook application
Recently, 60 sheets of Medite Vent breathable external sheathing panels were donated to the innovative ‘Schoolhouse Project’ at Burlington Danes Academy in West London, where a team of staff and students have built a timber frame house on the academy grounds.

Designed by architect Roderick James, working closely with the educational charity, The ARK Foundation, the project forms part of an ambitious scheme to improve pupils’ practical skills and boost self-esteem. It offered 20 students the opportunity to learn about carpentry, plumbing, roofing, insulation, sustainability and other key elements of the building trade.

Under the supervision of a skilled and knowledgeable team of professionals, students gained a wealth of valuable hands-on experience which included how to handle, cut and install the 60 sheets of Medite Vent. The Medite Vent panels were used within the single-storey timber building’s external roof construction.

“Pupils were handling the boards on site so the clean, lightweight and easy to handle Medite Vent proved ideal for the roofing application,” said Franc Farci, project manager. “As an educational construction site, the project has helped to show pupils how every single building component makes a difference to the performance of the whole building fabric.”