1.8.3 Phase Change Material
Use a phase change material (PCM) that absorbs and releases heat to reduce heating and cooling loads without the bulk required for conventional thermal mass strategies.
Phase change materials available for building applications are available in two forms. The first is a stand-alone sheet product installed within the wall or roof assembly such as BioPCM: a polyfilm with small pockets filled with a soya and palm oil based phase change material. The second form is microcapsules such as BASF’s Micronal: microscopic wax droplets inside hard acrylic polymer shells. The microcapsules are available in a water dispersion or powder and can be integrated into interior finish materials such as plaster and gypsum board.
Phase change materials absorb heat as they melt and then release heat as they solidify, just as water turning into ice. Phase change materials used in building applications solidify at much higher temperatures than water, typically within the comfort zone of 22 to 26 degrees Celsius. The point of solidification can be customized to best fit a given project application.
Significantly reduce or eliminate the need for active mechanical systems. BioPCM material cost is $3-4 per sf.
PCMs help to keep interior spaces at a comfortable temperature for longer periods of time, reducing heating and cooling loads. HVAC equipment can be reduced or, in some climates, eliminated. PCMs can also be used to decrease the temperature of roof assemblies. This both increases the life of roofing membranes, and increases the efficiency of roof-mounted PV arrays by lowering the PV panel temperature. Some PCM products, such as BioPCM, also include a built-in fire suppressant layer.
PCMs used to regulate interior temperatures should be installed on the inside face of insulation. They are a compliment to, rather than a replacement for, insulation. PCMs used to lower roof assembly temperature should be installed directly beneath the roofing finish panel or membrane. PCMs must be selected carefully in accordance with fire and building codes. Some are made from non-toxic, bio-based sources, whereas others are toxic. Oil-based PCMs are flammable and must be enclosed in proper containers and/or include added fires suppressants to mitigate this.
1.7.5 Fabric Energy Storage