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MolES Building, University of Washington, Seattle, United States

Monday 09 Jan 2012

Just a phase?

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10/01/12 daromarc, Paris
Nice, but what about hysteresis?
PCM capacity to retain/release heat drops progressively over the phase changing cycles, so what is to be done then?



Renewed interest in phase change materials as industry targets sustainable initiatives 

Bubbling under the surface of the world’s most sustainable building practices is a growing interest in phase change material (pcm) energy solutions. A variety of sources are on offer from the low-tech yak butter derivatives to a more industrial liquid/gas carbon dioxide product, with many manufacturers cashing in on the renewed interest in this green alternative. Interest in phase change materials began more than 30 years ago but it is only recently that the product is being recognised as an attractive and attainable solution to the high energy usage experienced by many new builds.

The basic premise of pcm is a material with a high heat of fusion which absorbs and releases energy as it changes state. Recently the AEC industry has seen a blossoming in the number of professionals considering such materials to bring down energy costs and provide sustainable solutions to the damaging effects that excessive energy usage can have on the environment.

A gel form of pcm developed from vegetable oils was selected for the almost-complete Molecular Engineering and Sciences (MolES) Building in Seattle for the University of Washington’s College of Engineering. Designed by US practice Zimmer Gunsul Frasca Architects with KPFF Consulting Engineers, Inc., the new 90,000 sq ft research building takes sustainable building design to a whole new level.

Panels with a thin 1.25cm strip of the bioPCM have been inserted into numerous wall and ceiling surfaces across the new MolES Building and despite their minimal application, Peter Horwarth, Executive Vice President of Phase Change Energy Solutions told New Scientist that the strips ‘act like the thermal mass of 25 centimetres of concrete’. The gel is installed in 5-10ml pockets to enhance the effectiveness of the product and reduce damage to the building should the surface become punctured.

In contrast to basic insulation, bioPCM raises the thermal mass of a building rather than its thermal resistance, increasing the time it takes for a structure to warm up or cool down. Phase change materials are fast becoming the savvy designer’s choice to ensure that a new building maintains a near constant temperature without the need for additional heating and cooling systems which rapidly increase a structure’s energy demands.

The advanced, eco-friendly approach of the University of Washington’s MolES Building does not end with pcms. An early energy analysis of the building concept suggested that solar gain through the façade would need to be reduced by 80% before natural ventilation could be initiated; as a result, the team reduced the glazed area of the façade by 41%, selected a high performance glazing which cut solar gain by 34% compared to the originally specified glass, and employed sun shading techniques which reduced peak insolation during mid-morning summer hours by 51%.

When confronted with minor issues in the operation of the ventilation stacks - which had to be reduced in area by 25% due to programmatic requirements - the team incorporated solar, wind and fan assists to ensure that the ventilation systems could remain in operation year round. The project is due to complete by the end of January and energy studies of the entire building are yet to be completed however an early assessment and specific ventilation models suggest that cooling energy for the office will be reduced by over 98%.

With impressive stats like this, pcms are becoming an ever-more attractive option for many building projects and their eco-credentials continue to crop up in numerous scientific journals and research documents. Only time will tell if this is a phase or whether pcms are here to stay.

Sian Disson
News Editor

Key Facts

Status Under construction
Value 0(m€)
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ZGF Architects LLP

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