Raising Sustainability with External Cladding Retrofits

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Wednesday, May 6th, 2015
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The retrofitting of the exterior of the building envelope is an excellent means of improving the sustainability and efficiency of existing properties while simultaneously achieving changes to their aesthetic appearance.

Non-load bearing cladding systems can be attached to the exterior walls of a building in order to improve its insulating properties, and significantly reduce the amount of energy required to either cool or heat its interior.

Karim Muri of Kingspan Insulation points out that external cladding can provide advantages compared to internal forms of insulation that require intrusive installation work, because they reduce the thermal bridging that occurs by means of the framing members of a building.

“Traditionally, batts are installed between the timber or steel framing members – however heat can still pass through those framing members by means of a process called ‘thermal bridging,’” said Muri. “This increases cooling and heating energy use and associated costs, as well as reduces internal comfort. Depending on wall construction and materials, thermal bridging can reduce Total R-values by up to 25 per cent.”

Muri noted that cladding solutions such as External Insulation and Finishing Systems (EIFS) address the problem of heat loss via thermal bridging by creating a more complete insulation shield around the exterior of the building.

“EIFS are installed over the frame, providing a ‘continuous insulation barrier’ around the building that reduces thermal bridging and associated heat loss or gain, and thus improves the lifetime energy efficiency,” he said.

Sustainability advocates are well aware of the efficiency gains that can be achieved via the installation of these external cladding systems, with Tone Wheeler, principal of Environa Studio and winner of the 2014 Milo Dunphy Award for Sustainable Architecture, referring to such solutions as “outsulation,” that enhance insulation from the outside of a building.

These insulation systems could make an immense difference to the efficiency of built environments, with estimates of the energy consumption reductions achievable via the installation of EIFS ranging from between 30 and 50 per cent.

Sarah Meyler of DuluxAcraTex added that many manufacturers of light cladding systems are striving to reduce the embodied impact on the environment of such products in order to raise their net sustainability.

“Many lightweight cladding systems are manufactured without the use of CFC’s or HCFCs, and have zero Ozone Depleting Potential (ODP) as well as low Global Warming Potential (GWP),” she said.

Other advantages of such systems include their low mass, which can impact structural considerations.

“EIFS can also have an impact on construction and engineering,” said Muri. “For example, for a project lot of say 600 square metre , Kooltherm K5 External Wall Board would have a total weight of 1.1 tonnes (for a 50-millimetre thick R2.5 board) to 1.6 tonnes (for an 80-millimetre R4.0 board).

“Compare this to AAC (aerated autoclaved concrete) blocks which would weigh almost 30 tonnes. This has significant implications for site deliveries and handling as well as implications for structural engineering and materials.”

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