The challenge for low energy house designers Princedale Ecohaus and Green Tomato, was to find solutions which would allow the 3-storey terrace house to perform to the very high levels demanded by the Passivhaus standard. This involved designing and developing all of the systems used in the house, including the airtight wall configuration.

Due to the terrace being located in a conservation area, all insulation had to be installed internally, so Kingspan’s Kooltherm range was chosen for the project as, with thermal conductivities as low as 0.020 W/m.K, relatively thin layers of insulation could be used to achieve the very high levels of thermal performance needed.

To make the house airtight, a continuous layer of OSB was installed on the roof, all external and party walls and the lower floor. Airtight tape and breathable membranes was then used to seal the OSB layer to the windows and doors, forming an airtight barrier and allowing the building to meet the required Passivhaus air tightness limit of 0.6 m3/hr/m2 at 50 Pa, ten times higher than the standard required by Approved Document L1A of the Building Regulations (England and Wales).

On the external walls 130mm and 50mm thicknesses of Kooltherm K12 Framing Board were fitted either side of the airtight barrier, while on the roof a 130mm layer of Kooltherm K7 Pitched Roof Board was installed between the rafters, with the airtight barrier and a second 50mm layer of K7 insulation fitted under the rafters. The finished roof and external walls produced an outstanding thermal performance with U-values of only 0.10 W/m2K. To further insulate the building a 50mm layer of K12 insulation was also installed on the party walls.

Tom Pakenham, Director of Green Tomato Energy said “Our client wanted to convert his house into a home fit for the future. Installing highly efficient, space-saving Kingspan Kooltherm allowed them to achieve this whilst minimizing the loss of internal space. The property is now being monitored to assess its performance in real life.”

Philip Proffit, director of Princedale Ecohaus Ltd. said “The benefits of retro-fitting houses to the Passivhaus standard are tremendous, not only are the annual heating bills for most houses reduced to less than £100 but the combination of an airtight barrier, insulation and airtight triple glazing and mechanical ventilation mean that nuisance outside noise such as traffic can be easily shut out, creating a tranquil environment within the house”.

By combining these measures with a heat recovering mechanical ventilation system, the house now needs less than 15 kWh per m2 of energy to be heated annually, far lower than the UK single family home average of 130 kWh per m2.

The house in Lena Gardens is one of two that have been retrofitted by Princedale Ecohaus Ltd to Passivhaus standards in the UK, the other property to have achieved this status thanks in part to Kingspan’s high performance insulation is a Victorian terrace house in Princedale Road, London. For this project, 50 and 150mm thicknesses of another Kingspan product, Thermawall TW55 insulation, was used to help it to become one of the first two UK retrofits to gain Passivhaus status.

All Kingspan Kooltherm products have a class 0 fire rated (Building Regulations for England and Wales) insulation core, are easy to handle and install and can provide consistent long-term thermal performance throughout a building’s life.