Sustainability to the core

Environmental accreditation via the likes of BREEAM, the BSI and ISO standards, undoubtedly lend an enviable level of authenticity to any development keen to showcase its green credentials. However, construction products must, first and foremost, be specified based on their suitability for application. Get that right and environmental performance – along with the associated accreditation – will naturally follow.

When looking to secure the sustainable credentials of any build, emphasis should be placed on the specification of robust building envelope systems that deliver the required thermal performance, the maximum level of air tightness and thermally efficient detailing as standard. It is only with these fundamental building blocks in place, that the sustainable credentials of the build can be independently accredited in a meaningful way.

Tests have proven that one of the primary causes of heat loss from a building is the result of poor detailing. These details include junctions and interfaces such as drip flashings, door and window jambs, internal gutters and parapets which, when poorly designed, can lead to significant levels of thermal bridging – the transfer of heat from the warm interior of a building to the cold exterior.

Details such as the drip – the junction between the external wall cladding and floor slab – which runs around the entire perimeter of the building can, if not designed and installed correctly, act as a huge heat conductor. Not only does this have a significant impact on the overall thermal performance of the envelope, but the resulting increase in thermal bridging can also increase the risk of condensation forming on the inside of  the building.

Pre-empting the issue at the building’s conception through the specification of thermally efficient details, which mitigate this ‘heat-sink’ effect, can deliver a significant thermal performance improvement, with previous schemes having seen benefits of up to 10% through efficient detailing alone. This translates into a direct saving on the building’s energy consumption, reducing the Buildings Emission Rate (BER) and thereby improving its Energy Performance Certification, resulting in greatly enhanced compliance with building regulations and sustainability targets.

Robust detailing, along with ever increasing levels of airtightness, have become a key focus for developers and architects, with the main aim of delivering significantly improved building envelope performance. Improvements in air tightness alone have been proven to deliver a reduction in a building’s associated heat loss by as much as 30% and are often achieved at no extra cost to the build. This is only possible, however, through the specification of proven cladding systems which are tested and assessed as a complete assembly and installed by reputable, trained installers.

The specification of such cladding systems also provides the designer with the ability to assess the environmental accreditation of the system in its entirety, with many building envelope systems carrying independently assessed Environmental Product Declarations (EPD’s) detailing their Life Cycle Analysis and embodied CO2 content. This is generally combined with the cladding manufacturers Environmental Management System (EMS) certification through the likes of ISO 14001 and any responsible sourcing qualifications that may be available for their construction products through standards like BES 6001. These all aid towards achieving the highest possible BREEAM assessment ratings.

Reputable building envelope specialists have dedicated technical teams assigned to developing a ‘gold standard’. This highlights precisely detailed specifications, along with U-value, psi-value and f-factor calculations which can be included in the building’s SBEM (Simplified Building Energy Model) calculations – a pre requisite for all buildings being constructed today in the UK.

Along with improved thermal detailing, there are a number of other areas which can be addressed through the very fabric of the building. These include: acoustic performance, fire performance, guarantees (particularly in humid or corrosive environments) and Non-Fragility of roofing systems, which is of utmost importance given the ever increasing application of roof mounted PV an
d Solar Thermal systems. The smart money of course is on the system that can deliver all of the above.

Andrew Brewster, Project Development Manager, CA Group Limited.

 

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