Improving the appearance and thermal efficiency of buildings

Structural defects and poor thermal efficiency are issues affecting a significant number of non-traditional and prefabricated concrete (PRC) buildings. Andy Carter, Structherm’s technical manager, looks at how Structural External Wall Insulation (SEWI) can be used to remediate these problems

Many buildings, particularly those constructed during the 1960s and 1970s, suffer from inadequate thermal insulation, significant thermal bridging and subsequent condensation problems. Over time, the deteriorating fabric leads to a gradual reduction in structural effectiveness, particularly at construction joints and junctions between components. This is exacerbated by poor concrete cover and/or chloride contamination leading to corrosion of reinforcement in the structural elements. Weather tightness may also be severely reduced.

SEWI offers the perfect solution as it provides a cost effective method of extending the life of a defective property – which might otherwise have to be demolished – while improving its external appearance and thermal efficiency. It also offers a major advantage over other remedial solutions as installation is carried out externally, allowing residents to stay in their homes during refurbishment. It can be used for over cladding non-traditional, no-fines concrete and defective housing (both low and high), reconfiguring building facades, enclosing balconies or walkways and forming new or existing parapets.

Each SEWI panel consists of a galvanised or stainless steel structure with a rigid insulation core. The type of insulation used depends on the U value required, but generally it is either mineral fibre, polyisocyanurate (PIR) or enhanced expanded polystyrene (EEPS). This greatly improves the thermal performance of the building, reducing both CO2 emissions and on-going energy costs for residents.

The panels are attached to the existing building using special fixings and then joined together with mesh to provide a rigid, continuous envelope that offers complete structural integrity without the need to alter foundations or drainage, saving time and money. A substantial layer of basecoat render is then applied, which works with the panels to provide a high degree of strength and an impact resistance of 10Nm.

The refurbishment work is completed with a top coat render. There are a wide choice of contemporary acrylic and silicone finishes in many different colours available, while a traditional finish can be achieved by using our brick effect render, stone effect render or dash finishes.

To ensure the right type of SEWI system is specified companies may offer a comprehensive technical service for each stage of the refurbishment project, from initial concept through to completion. This can include design and feasibility proposals, detailed analysis of the structure to determine the optimum method for fixing the SEWI panels, full specifications, structural calculations for the overall stability of the structure (provided as submissions for building control approval) and thermal calculations.