Thermal Mass Systems : A radical development

“Anyone who has spent any time in a timber, glass or steel framed building in the height of summer understands the discomfort of steeply rising temperatures. Anyone who has had to meet the bill for the air-conditioning – or who is concerned about climate change from the resulting CO2 emissions – understands the real cost of this problem…”
I had been aware for some time about the twin problems of comfort and energy consumption posed by low-inertia lightweight-structure buildings. Steel, aluminium and timber framed buildings offer many advantages including exciting design potential, but they usually demand extensive and expensive air-conditioning systems to compensate for the temperature peaks caused by solar gains and by internal activity. It occurred to me that one solution could be a lightweight, stable and easy-to-install system for adding thermal mass to such structures, preferably specified at the build stage, but also suitable for retro-fitting.

From the earliest thinking it was clear that Phase Change Materials held the key. As part of the DuPont Tyvek business, (breather membranes to manage moisture and thermal performance of the building envelope) I was in the perfect position to explore the ideas that eventually resulted in DuPont Energain. The wealth of experience within the DuPont Building Innovations platform meant there was a strong knowledge of the architecture and construction market. Furthermore, by also working closely with a colleague in the DuPont Packaging & Industrial Polymers division, I had access to the laboratories, resources and expertise to develop both the core ingredients of the material compound and the processes to manufacture on an industrial scale.

So what is DuPont Energain and what makes it such a radical development? Quite simply it is a thermal mass panel with valuable energy saving and temperature control properties. It has been designed as a practical answer not only to increasing the comfort (and therefore productivity) of buildings, but also to reducing their CO2 footprint – a crucial issue in today’s meteorological and political climate. In addition, we have been mindful of issues such as ease of installation, stable performance and the long term cost savings such a product can offer.

DuPont Energain is composed of a Phase Change Material made from paraffin, encapsulated in a DuPont copolymer at a 60% – 40% ratio, avoiding staining effect. The panel is laminated on either side in a high quality aluminium sheet. The system works by employing the capability of the PCM to absorb and release heat. Simplified, the compound has a melt point of 22°C. During the melting phase it absorbs heat from the room and stores it. When the interior temperature drops, it re-solidifies and releases warmth back into the room. Working in this way, the system can not only minimise uncomfortable temperature peaks by up to 7°C, it can save up to 35% of air conditioning costs (and 15% of heating costs – particularly at night time and mid-season).

For an industry that’s always concerned with timescales and labour costs, the product offers further advantages. In terms of installation, no extensive special training or complicated processes or equipment are involved. The pre-cut and pre-taped panels are lightweight and can be easily cut and then screwed, nailed or stapled in place. (DuPont Energain aluminium tape must be applied to any new cuts or areas where the paraffin and polymer compound is exposed). The panels are positioned in between the insulation and the plasterboard, or between inner partition walls. They can also be installed between the attic finishing and roofing insulation or behind the ceiling finishing.

DuPont Energain is suitable for a wide range of commercial, public and residential buildings and allows architects to continue designing dramatic, modern structures with fewer concerns about sustainability and end-user satisfaction. Designed to be fitted alongside standard materials such as insulation, plasterboard and partition walls, DuPont Energain works together with mechanical ventilation systems and in co-ordination with heating and air conditioning systems. Currently, while the installation of the thermal mass panels does not replace the need for air conditioning it may allow for a reduction in the size – and definitely in the use – of AC units. Ultimately, with further development, it may be possible to eliminate the need for air conditioning all together.

In order to help engineers and specifiers calculate precisely how much of the material is needed and where, a DuPont proprietary version of the numerical software programme, CoDyBa (version CDB_dDDN_V2), has been specially created. The software illustrates the thermal behaviour of a specific building with – and without – DuPont Energain, including energy savings and CO2 emission reductions. These simulations will be made available through the DuPont Energain sales and technical teams who will be on hand to advise. The panels are then delivered on site, ready to install.

We have conducted experiments to test DuPont Energain in a real life environment at a test site in France. One of the objectives was to prove the functionality of the panel when installed in the walls and/or in the roof structure of a real house. For the first phase of testing the decision was taken to use the most critical part of the structure, the attic, in order to verify performance in a worst case scenario of conditions. DuPont Energain panels were installed behind the plasterboards, in the walls and in the ceiling of one of the test rooms. A second room with an identical structural and sensor setup, but without the panels installed, was used as the control. A third room, located in between the two test cells, was used as a buffer zone.

The tests continue, but initial results have demonstrated the potential for valuable savings in both energy costs and CO2 emissions in structures installed with DuPont Energain – and for increased interior comfort levels, especially in warmer conditions. Further testing in varying climatic conditions and in different types of structures is in the pipeline, with results expected later in 2007.

In an encouraging vote of confidence, I am happy to say that DuPont Energain has been awarded a LIFE Grant from the European Commission as part of its support package for Energy Efficient Buildings Systems; furthermore the product has been shortlisted for the Daily Telegraph / Carbon Trust Awards. DuPont Energain is now available to engineers, architects, builders and specifiers in the UK.

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