There is considera
ble evidence to support the fact that overheating of buildings in the UK is becoming an increasing problem. In a recent survey (October 2015), on behalf of WSP:Parsons Brinckerhoff, 83% of the 1,005 London households surveyed stated that they had experienced at least one period of overheating during that summer. Part of the problem could be due to the law of unintended consequences; e.g. the demand for reduced energy consumption/lower carbon emissions has led to increased airtightness and insulation in new homes. Modern building methods have also had an adverse effect as dry lining (via dot and dab or battens) effectively decouples any thermal mass away from the room air. It’s highly unlikely that the industry will revert to wet plastering on concrete blockwork so the use of phase change materials, perhaps in plaster or clay boards, would seem like an ideal method for providing effective thermal mass for modern buildings.
Although PCMs have been used successfully in several applications their use has not been widespread. Discussions with many architects and engineers, during the last few years, have led me to suggest that this could be due to several factors, which I call the 4Ps:
Price – not surprisingly this is the most often quoted reason against the use of PCMs. With a PCM plasterboard costing, say, £70/m2 but looking virtually the same as a standard plasterboard, marketing the product can be an uphill task. The fact that a PCM plasterboard, depending on PCM content/enthalpy, could possess thermal mass equivalent to 40 – 55mm of concrete is often ignored.
Performance – potential clients are often cautious about being a first adopter and tend to ask for details of buildings where PCMs have been used and performance monitored. Perhaps surprisingly, there is very little comprehensive use data available.
Proof – in the UK, the thermal performance of a building has to be assessed using suitable, approved software. Unfortunately, neither SAP (used for homes) nor SBEM (for non-domestic buildings) can calculate the effects of using PCMs – they rely on the specific heats of the construction materials remaining constant. Dynamic simulation modelling software can cope with PCMs but require a “PCM module” into which the relevant data can be input by the user. In the UK the only DSM software capable of determining the effects of PCMs is DesignBuilder (https://www.designbuilder.co.uk/), which uses the EnergyPlus calculating engine. However, PCM product suppliers and potential clients need to be able to use software such as DesignBuilder or EnergyPlus to show the benefits of their products.
Promotion – all three of the Ps above need to be addressed to enable successful marketing of PCM-based products to take place. If the successful marketing of PCMs into the construction industry is to occur then, perhaps, the various interested parties need to act together to promote their use. In the meantime, it is the auto industry that seems to be more interested in these products. The latest announcement by Constellium NV (http://www.autonews.com/article/20170731/OEM10/170739985/ev-bodies-part-of-the-power-source) is just one of many examples of auto industry interest in PCMs.
