Phase change materials (PCM) provide thermal mass, but on a much smaller scale. PCMs work by melting and solidifying at a specific temperature — heat is absorbed at the solid state, and when the material reaches a predetermined temperature, it changes to a liquid and releases the stored energy (heat). When the temperature falls below a predetermined degree, the PCM re-solidifys and the process repeats. The most common PCMs come in the form of paraffin, fatty acids and salt hydrates, each with their own advantages and disadvantages. Most PCMs must be encapsulated to be stored and prevent evaporation and absorption. There are several sectors in building industry that are looking to incorporate PCMs into their materials and products — some examples of this include drywall, windows, concrete and insulation. For example, when PCMs are embedded into drywall, an entire building is capable of storing energy, rather than just it's exterior walls (where masonry is typically used). All walls that are sheathed with PCM embedded drywall are able to absorb and release heat around-the-clock to maintain a predetermined and desired temperature. By using drywall embedded with PCMs as thermal mass, instead of masonry or concrete, the building gains square footage that typically would've been lost to thick walls, and needs less structural support, which can get very expensive. Other current PCM applications include:
- BioPCM: BioPCM can be integrated into new construction or retrofitted into existing. It is a rolled mat that contains PCM; the mat is installed between insulation and drywall layers and can be located in walls and ceiling.
- GlassX: GlassX is an insulated glazing unit that can be used as full glass walls and windows. The unit has an outer pane of glass that reflects high-angle sun and allows low-angle sunlight to pass. Sunlight that is transmitted through this outer pane of glass passes through inner polycarbonate channels that are embedded with salt-hydrate PCMs. These PCMs store the heat from the sunlight, and release the heat to the interior of the building as the temperature cools.
- ThermalCORE: Made by National Gypsum/BASF Corporation, ThermalCORE is a drywall panel embedded with paraffin PCM. The microscopic paraffin capsules absorb and distribute heat as the wax melts and solidifies with temperature fluctuations. ThermalCORE is not currently commercially available for purchase and is still undergoing testing.