REINFORCED CONCRETE FORWARDS FABRIC FIRST APPROACH FOR HEAT RESILIENCE

The British Association of Reinforcement (BAR) has welcomed the fabric first approach advocated by the recent Environment Audit Committee report ‘Heat resilience and sustainable cooling’.

The report, spearheaded by Oxford University, urges the introduction of a national heat resilience strategy to prepare the UK for the impacts of a warming world. It highlights a fabric-first and passive cooling approach that includes managing internal heat via exposed thermal mass with passive ventilation.
A fabric first approach could realise the potential of the inherent thermal mass benefits of concrete construction to cool buildings without the need for energy guzzling, carbon emitting air-conditioning.

Concrete thermal mass, when used in combination with natural night time ventilation and cooling, can reduce or even eliminate the need for air-conditioning. Often referred to as Fabric Energy Storage (FES), the basic approach is to expose the soffit of concrete floor slabs which can then absorb heat gains during warm weather and so reduce the internal temperature. The use of cooler night-time air ventilation or embedded water-cooling cools the soffits in readiness for the following day. The best level of thermal mass is provided by heavyweight construction. Lightweight construction such as steel and timber structures do not offer a comparable level of heat absorption.

Steve Elliott, BAR Chairman, explained: “Concrete construction readily lends itself to a fabric first approach to cool buildings especially when used as part of an integrated passive design solution that includes building orientation, shading and natural ventilation. This can reduce significantly the reliance on air-conditioning and in return reduce the level of carbon emissions.

He added: “Some passively cooled concrete buildings will have an initial higher embodied CO2. However, that will be quickly offset by the reductions in ongoing operational CO2 which can range from just one to six years,” said Elliott. “A lightweight constructed building may have an initial lower build CO2 impact but over the building’s operational life time it will most likely have a far higher whole life CO2 emission impact.”

The use of concrete construction does raise questions concerning the level of embodied CO2 when compared to other structural materials admitted Elliott who pointed out that the cement and concrete industry has made considerable investment to deliver a 53% reduction in CO2 emissions since 1990 and is committed going beyond net zero and be net negative – removing more CO2 than is produced – by 2050.