Class O Armaflex materials have been selected to provide both thermal and acoustic insulation for air conditioning ductwork during a major restoration project undertaken at the Belfast City Hall. This magnificent listed building, which was opened in 1906 and survived severe wartime damage, is located in the heart of Belfast and is a source of great civic pride. Guided tours are popular with tourists and locals alike, to view reception and banqueting halls which are complemented by the stained glass windows and select foreign marbles used in their design and construction.
The building, which is depicted on all banknotes in Northern Ireland, has recently undergone extensive renovations which included a comprehensive overhaul of the air conditioning system. This project presented several challenges, including space as the existing ductwork had not been designed to accommodate the thickness of modern insulation which provides better thermal efficiency. A second problem involved suppression of the mechanical droning sound generated by the air-handling units which was at odds with the subdued, relaxing ambience required for the lavish interiors of the city hall.


The application of 1716m2 Class O Armaflex materials has successfully resolved both the thermal and acoustic problems at the same time. Internally lining the ductwork walls with 25mm thick Armaflex insulation has ensured that energy saving targets were achieved, while noise propagation generated by low frequencies through frame resonance has also been reduced to an acceptable level.

The dual combination of thermal efficiency and acoustic attenuation provided by the Armaflex materials effectively halved the insulation thickness requirements. This minimised the material costs, as well as reducing the installation to a single application process, further reducing both time and costs for the work undertaken.

The internal lining of ductwork is unusual in the UK, but is established common practice in many other countries including the USA. The Class O Armaflex insulation is 100% dust and fibre free, ensuring that it is safe to use within air ducting, without any risk of fibre migration into the air stream or the building interior. It is also the only insulation material to feature built-in Microban anti-microbial protection, which together with the closed-cell structure lining helps prevent both bacterial and mould growth on the insulation lining. This is an essential consideration when looking to minimise the onset of harmful 'sick building syndrome', particularly where ducting has been internally lined.

Consultant Mott McDonald, who initially identified Class O Armaflex as the appropriate material for use on the project, confirms that both client and the project contractors Sharpe Group were also suitably impressed with his choice. Mott believes that 'Class O Armaflex performed well beyond our expectations. We have been looking for an integrated thermal and acoustic insulation for some time and this product is really ideal.'