Alumasc’s Swisslab External Wall Insulation (EWI) system has been used in the refurbishment of Sunningdale on The Wirral; one of five high rise blocks earmarked for renovation by Magenta Living following their transfer from Wirral Borough Council in 2005.
The 15-storey high rise was constructed in the 1960s using the Bison method of pre-cast concrete panels. As a result of its Bison construction, the mastic sealant between the concrete panels had degraded over time leading to water ingress from wind and rain.
Alumasc products were specified as a result of their success in other similar projects, and subsequent positive reputation.
3000m2 of Swisslab External Wall Insulation was installed by BLD Construction Facades Ltd. Swisslab was chosen as only 60mm Phenolic (Kooltherm K5 EWB board) insulation was required to achieve the target U value target of 0.25 w/m2k. This thinner layer, when compared to EPS or mineral wool, was ideal for fitting around the challenging features of the building, such as balconies, and also meant that an additional fire barrier was not needed because of Swisslab's full scale fire testing credentials.
Sunningdale was finished using Silkolitt Silicone Render 1.5mm in off-white, grey and yellow/orange with traditional clay brick slips at ground floor level. This has improved its aesthetic appearance and is low maintenance.
CHALLENGES AND AIMS
Due to the building's position at the mouth of the Mersey Estuary, the main challenge was high wind speed, sometimes reaching 1.9N/m2. As well as the standard implementation of Alumasc's High Rise Policy, this high wind speed meant that Alumasc's technical support team had to work closely with consulting engineers to ensure the EWI's effectiveness. The result was that the EWI was fixed through the scrim layer to increase resistance. The team also had to allow the render a faster "going off" time due to the high winds.
The substrate on the Bison concrete panels was varied and additional work was required in areas where a larger base profile was needed to compensate for this. Additional challenges were presented by features such as balconies, which demanded a thin insulation layer to fit around the detailing without encroaching onto it.
In addition, heat reflective paint was used to overcome the historic problems of heat retention at the top of the building.
Residents of Sunningdale now live in more attractive and warmer homes with a U-value reduction from 1.15 W/m2k to 0.25W/m2k achieved.
Ian Murray, Project Manager for Magenta Living, said:
“Since its refurbishment in the mid-1980s Sunningdale has had its own distinct identity within the local community. Following the completion of this latest refurbishment, Sunningdale now displays a more contemporary appearance due to the transformed facade. Both the external wall insulation system and the new glass balustrades to the balconies, have provided a completely new look whilst at the same time maintaining its distinctive individuality.”