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Cavity Window Fittings: BBA ACD’s V RCD’s

1 August 2007

“Standards of building have been controlled in the UK in one form or another since 1189 when the Assize of Buildings in London first introduced the forerunner to the modern building codes. In 1667, the year following the Great Fire on London, which saw the rapid destruction of the closely packed houses it was realised that some kind of improved regulation was needed. The result was the adoption of the first building codes aimed at making houses more robust against fire.

Two hundred years on and the industrial revolution with its ever-expanding urban population, poor living conditions and problems with damp and lack of ventilation became the biggest concerns. Frequent outbreaks of diseases eventually prompted the government to take action and what had by then become known as Building Control took on the greater role of Health and Safety through the first Public Health Act in 1875. This Act had two major revisions in the nineteenth century resulting in the first set of national building standards, the Building Regulations being introduced in 1965.

Today the Building Regulations are constantly being reviewed and this is only right in order to meet the need for better, safer buildings. Today it is a completely different set of factors that are facing the building industry. No longer is there the same threat of fire or severely unhealthy homes. Today, as everyone is becoming more aware of the environment and the threat of global warming, the latest regulations are focused on improving the thermal performance of dwellings.

The latest revisions to the Building Regulations Part L aims to cut carbon dioxide emissions from dwellings by around 20% on the original Approved Document L - 2002. These will again be tightened in 2010 and 2013, as part of the Government’s aim to make all new housing zero carbon by 2016, in line with the Code for Sustainable Homes. These constant updates in the regulations mean that the fenestration sector needs to have an eye on the future when designing building components simply to keep up with the regulations.

Many manufacturers are now also gaining BBA certification on their products because these are recognised by specifiers as proof that the products they cover have been rigorously assessed and will therefore guarantee compliance with Building Regulations. Every Agrément Certificate contains important data on durability, installation and compliance with Building Regulations and these are often shown as either robust construction details (RCD) or accredited construction details (ACD).

However, when it comes to cavity closers there is still an element of confusion around compliance because the BBA certificate refers to both RCD’s and ACD’s. Normally this wouldn’t pose a problem as both would have the same outcome. However with cavity closers, measuring the thermal performance is different for RCD than it is for the newer ACD. The current BBA certificate refers to both these Construction Details because the Approved Documents which supports the Building Regulations allows it and the current issue of the Approved Document (Part L) refers to both RCD and ACD! This is probably because the ACD’s were not fully published when the Approved Documents were issued. The result is that even though both are valid methods of measuring thermal performance, it does cause confusion in the marketplace.

The newer updated ACD’s have been developed to assist the construction industry in achieving the higher performance standards required to demonstrate compliance with the tighter energy efficiency requirements of the Building Regulations. RCD’s were introduced earlier - alongside the 2002 Building Regulations and therefore we believe in time will be wholly replaced by ACD. However, this anomaly is unlikely to be corrected until Approved Documents are updated to refer only to ACD’s and the reference to RCD’s is removed. For now, BBA will continue to refer to ACD’s if that higher standard of compliance is met and only refer to RCD standards if only RCD standards are met.

When developing our new Cavity Closer, we worked towards the higher standards required by the ACD, rather than RCD. We are therefore encouraging building designers to ensure they refer to the Accredited Construction Details (ACDs) within the BBA. By doing this it will ensure that they are already working to the appropriate Construction Details when the Approved Documents are indeed updated again and references to RCD, we believe, will be removed. Of course, some may still work to RCD and, to be fair, this too contains a checklist by which the Designer, Constructor and Building Control Body can demonstrate compliance. However, this doesn’t get away from the fact that it is likely to be superceded by the ACD.

For the time being, this contradiction in the Approved Documents will continue to cause confusion with its reference to both Construction Details. The stance we have taken on this has been to develop our cavity closer to comply with the new ACD which meant that in September 2006 we were one of the first to offer a Cavity Closer System to be issued with a BBA certificate that confirmed to ACD, the majority in the market still comply with RCD. Satisfying the requirements of the ACD’s also automatically covers RCD too, so it again makes sense to use a cavity closer that conforms to the new ACD.

In an ideal world, many would like to see the revision of the current Approved Documents that refers to both RCD and ACD with new ones issued that refers to ACD only, which would be a much clearer system. Until then we would still encourage all building designers to choose cavity closers carefully and select those that are deemed to satisfy the most up to date standards.

So there you have it. Building Regulations in one form or another have been with us now for well over seven hundred years, which in itself is a phenomenal achievement. The effect they have had on the building industry has been truly amazing and, just like in times gone by, their help in addressing the issues of the day are as relevant now as they ever have been.

Today the pressing need is to create sustainable environmentally sound developments with reduced carbon dioxide emissions. We can all help in this area by ensuring we all work to the newer tightened regulations wherever possible.”

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