1875, Wesley Chapel Residential Development, St. Helier, Jersey
Over 220 metres of Ancon Isotec thermal break have been installed by Dandara at the slab-to-balcony connections on this stylish residential development in St. Helier. The Ancon system minimises the effect of cold bridging at the construction joint, reducing energy use in the building.
The development, designed by Waddington Architects, comprises 48 modern apartments and 9 townhouses hidden behind the striking façade of a classical methodist chapel originally built in 1875, which gives the development its unusual name.
Energy efficiency is becoming increasingly important in today’s sustainable building designs and the thermal performance of the building envelope is a key design consideration. At the same time, architects are looking to create stylish developments that combine high density occupancy with accessible outdoor space.
Balconies often provide the answer, but as they typically pass through the building envelope, the fixing detail requires special attention to minimise thermal bridging and its various consequences. Thermal bridges occur where the insulation layer is penetrated by a material with a relatively high thermal conductivity.
Traditionally, concrete balconies were constructed by simply extending the floor as a continuous protruding slab. This results in local heat losses and higher energy use, as the concrete creates a direct path for heat to escape and cold to enter the building. Cold internal surface temperatures can also cause condensation and mould growth, resulting in potentially harmful living conditions for residents.
In extreme cases, buildings are condemned as remedial action can be unsuccessful. Proprietary thermal break systems are now commonplace on construction plans.
Ancon Isotec thermally insulated connectors are specifically designed to minimise heat loss at concrete-to-concrete applications, while also offering the necessary strength to maintain structural integrity. They provide a thermal break by inserting insulation, which has a very low thermal conductivity, between the concrete elements which have a relatively high conductivity. As a critical structural component, they feature the minimal amount of metalwork required to transfer moment, shear, tension and compression forces, without adding considerably to the thermal conductivity of the joint.
Each unit is manufactured as a non-deformable cage offering high rigidity and dimensional stability, and the insulation component comprises Rockwool mineral wool that offers inherent fire-resistant qualities. However, the main reason Isotec was selected on this project was its stainless steel tensile and shear reinforcement, which offer improvements in both thermal efficiency and corrosion resistance, plus a reduced concrete cover, over carbon steel systems. With no structural welding or point of weakness, the 100% stainless steel system from Ancon was preferred to other systems on the market.
An additional benefit of the Ancon system is the use of short compression studs instead of long compression bars which offer greater concrete design flexibility and simplify installation in the 170mm slab depth.
A once ruined chapel, this project has succeeded in bringing an architectural gem back into 21st century life by converting it into contemporary and energy efficient town centre residences. The Ancon system will go on contributing to the thermal efficiency of the homes, throughout the life of the structure.
Isotec is a high performance thermal break system for concrete-to-concrete applications.
Ancon’s connectors minimise heat loss at balcony locations while maintaining structural integrity.
Ancon is a proud sponsor of the 6th UK DISC (Developments in Structural Concrete) Conference, taking place at the Institution of Structural Engineers in London, on 29 November 2018.
Ancon’s recently-extended head office in Sheffield is now home to a unique piece of wall art, thanks to the artistic talents of one of its employees.