First Passivhaus in Wiltshire achieved with help from MEDITE VENT and SMARTPLY AIRTIGHT

MEDITE VENT and SMARTPLY AIRTIGHT proved to be a winning combination for the first oak frame Passivhaus to be built in the heart of Wiltshire, South West England.

Built by award-winning construction company Erigo Developments, Seldom Seen, a private detached residence, was at the time of completion the first house in Wiltshire to meet the Passivhaus standard. It still ranks as only the eighth certified Passivhaus in the South West of England.

Designed around a traditional oak frame and finished in oak cladding, the house was strategically sympathetic to its rural Area of Outstanding Natural Beauty (AONB) setting.

The combination of MEDITE VENT and SMARTPLY AIRTIGHT helped to achieve its Passivhaus status.

Rebecca Thursby, Director of Erigo Developments commented: “At the time, there was nothing else on the market that fulfilled its role in this location. We used an oak frame to create the external envelope and then choose both MEDITE VENT and SMARTPLY AIRTIGHT to achieve the level of airtightness required to meet the Passivhaus standard. We managed to get the air tightness down to 0.38 ACH @ 50 Pascals, which is very good.”

To reach Passivhaus standard, a building must achieve an airtightness level of 0.6ACH (Air Change per Hour) at 50 Pascals or less. In other words, the volume of uncontrolled air leakages in 1 hour must be less than 0.6 times the overall building volume when the difference in air pressure between the indoors and outdoors is 50 Pascals. Named after French mathematician and physicist Blaise Pascal, ‘Pascals’ is the unit by which pressure is measured. In this case, it indicates the air pressure difference between inside the building and outside the building for the airtightness test. Reaching an airtightness level of 0.38 can be considered a remarkable achievement.

Perfect for use in low energy buildings, MEDITE VENT is a high performance, breathable sheathing panel, suitable for use in timber frame structures. It boasts high racking strength in excess of Category 1 requirements, and high vapour permeability alongside weather resistance. Its extremely low vapour diffusion factor helps to prevent condensation and because it is manufactured with no added formaldehyde, it contributes to both a healthier working environment for installing contractors and a healthier living environment for building occupants.

This intelligently formulated panel is teamed with SMARTPLY AIRTIGHT, an airtight structural OSB/3 panel with integrated vapour control properties, used as structural sheathing in timber frame buildings. These features eliminate the need for additional Air and Vapour Control layer (AVCL) membranes. Its coating also provides a durable, smooth surface perfect for the use of airtight tape at the panel joints. SMARTPLY’s in-house speciality surfacing technology provides this integrated vapour barrier, which delivers high and constant vapour resistance across the whole surface.

For this project, the timber frame was in-filled with Icyenene sprayfoam insulation, with SMARTPLY AIRTIGHT lining the interior, alongside plasterboard facing the room. MEDITE VENT was installed on the exterior of the spray foam, which was then topped with Tyvek wrap and finished with the timber cladding.

MEDITE SMARTPLY’s entire product range, including MEDITE VENT and SMARTPLY AIRTIGHT, is manufactured with FSC® certified Irish timber, from their own sustainably managed forests, demonstrating a clear supply chain and manufacturing process.

Being conscious of how this industry impacts the environment is also something that Erigo Developments takes very seriously. Erigo is an award-winning construction company that puts an exceptionally strong focus on being environmentally responsible. The company demonstrates this by selecting carbon responsible materials and always aiming to achieve zero non-hazardous waste to landfill in all of their projects.

“We've made a commitment that we're only going to build to a Passivhaus standard going forward, and to build with carbon responsible materials,” continued Rebecca. “I think everyone needs to do their bit to combat climate change.”

“I think that building regulations need to go further in terms of power requirements and what's needed from houses now to achieve energy efficiency. That way, everyone knows what they can do in order to reduce their energy demands. There also needs to be more incentives in place to make people choose carbon responsible materials.”

The use of MEDITE VENT and SMARTPLY AIRTIGHT provides a winning formula for sustainable building.