The State of Insulation
Over the past century, building insulation has transformed many times. The latest addition is the incorporation of phase changing materials (PCMs) within the wall assembly. As the name suggests, PCMs are materials that change from one phase (state of matter) to another at a designated temperature. The oldest use of PCM is ice/water, which does not have any capacity for heat storage. There are three newer categories of PCMs that can flex through a range of thermal storage capacities; salt hydrates, paraffins, and biobased PCMs. These new materials are an adaptation of the well-known concept of using thermal mass for spatial temperature regulation.
One of the first documented applications of a PCM was in 1948 in a house designed by Maria Telkes, located in Dover, MA. A salt based PCM that was placed in drums and used fans to circulate the residual heat throughout the house. The system could maintain a comfortable temperature in the house for 11 sunless days during the winter months.
PCMs have been studied as thermal mass components for over fifty years and are shown to reduce the heating and cooling loads up to thirty percent. Initially PCMs suffered some setbacks due to these factors: an expensive upfront cost, the lifespan of its phase changing abilities, leaky packaging. The biggest adverse attribute being the use of paraffinic hydrocarbon based material. This type of material increases the flammability of the wall assembly and is known to be corrosive which created packaging issues. PCMs today are generally salt hydrate, or biobased fatty acids. These natural compounds reduce the flammability and toxic nature of the material. Salt hydrate compounds have high volume changes between phase changes, creating issues with packaging. This leaves the fire resistant biobased (fatty acids) PCMs as the most stable and widely used compound today. The average PCM has a life cycle of thirty years, and is now offered in a variety of integrated solutions.
The most commonly used PCM are pouch-based sheets that are integrated into an interior air vapor barrier. There are now a few companies offering gypsum wallboard (GWB) that has PCM particles integrated within its core. The PCM integrated GWB has fiberglass facing instead of paper, but otherwise no different than standard GWB. The ever changing technologies contained within wall assemblies are exciting to follow, and allow for customizable adaptation to meet the clients’ needs.