Chester Balmore project, designed to achieve Code for Sustainable Homes Level 4, chose the Schöck Isokorb type A as a cost-effective and more thermally efficient alternative to wrapped parapets.
Located near Highgate in North London, the Chester Balmore project consists of three elegant brick-clad blocks, housing a contemporary collection of 53 super-insulated one, two and three-bedroom flats, all set around a landscaped courtyard. The development is designed to achieve Code for Sustainable Homes Level 4 and the high levels of insulation employ good use of solar and internal heat gains, plus excellent air tightness and minimal thermal bridges. The virtually airtight envelope is constructed using reinforced concrete and blockwork and has a 250mm wall cavity filled with EPS, along with a special resin to hold the material in position. Including the cavity, the walls are half a metre thick and the windows are all triple glazed. It is claimed that the air tightness on the Chester Balmore development is around twenty times better than that required by Building Regulations.
Preventing thermal bridging along the parapets was a critical consideration for such a high performance development, because as with balconies, parapets can allow conductive materials to transfer energy through the thermal barrier. Conventionally, in the majority of cases, the method of insulating parapets and parapet walls is to wrap the perimeter of the wall with an insulation barrier. However, the Schöck Isokorb type A offers a cost-effective and more thermally efficient alternative. Its 60mm insulation thickness results in low psi-values and therefore significantly reduces heat loss – and there is no wrapping required. It permits a more sophisticated construction opportunity for greater freedom of design and allows flexible distance between elements according to load requirements. An added benefit being there is no risk of any additional thermal bridging through balustrade fixings. Other key factors are durability and water impermeability. The Isokorb type A solution does not require maintenance and there is no risk of expensive restoration due to waterproofing problems. Whereas wrapped components can be likened to an insulated flat roof, with many of the associated problems. They are prone to damage and almost inevitable repair and maintenance outlay, particularly where railings or covers pierce the insulating layer. With thermally separated parapets, railings and covers can be attached directly into the concrete. The Isokorb type A provides BBA Certification and LABC Registration and meets full compliance with the relevant UK building regulations. In addition, there is also compliance with the Government Standard Assessment Procedure, SAP 2009, concerning CO2 emissions from buildings and respectively heat losses through non-repeating thermal bridges.
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