Using Phase-Change Materials for Sustainable Building Envelopes

As demand increases for sustainable buildings, researchers around the world are looking into materials and methods to expand thermal energy options.

From the industry that brought us thermal mass floors and Trombe walls, the focus is shifting to phase-change material (PCM) technology for construction applications. Sustainable building components seem like a promising use for PCMs.

PCM Components

PCMs present an opportunity for sustainable building methods because of select melting points that enable them to passively store and release heat. Used in key locations inside a building, especially the building envelope, they can help regulate indoor temperatures.

One of these materials that melts or solidifies at what is typically considered target room temperatures is paraffin wax. Paraffin wax absorbs heat similar to thermal mass. Then, depending on its chemical constituents, the wax melts into a liquid at just under 80 degrees F. As the room cools below that temperature threshold, the wax begins to solidify, releasing the heat it absorbed earlier. Ultrafine granules, aka. nano-particles, of paraffin wax can be added to building materials like drywall.

Drywall/Wallboard

One example of PCM drywall is Knauf Comfortboard, a 2016 Architecture & Design Sustainability Award finalist in Australia and winner of the Danish Building Industry Energy Award the same year. The wallboard is described by Archello.com as being specified by architects on several projects in Austria and Canada as recently as 2021. National Gypsum developed a similar product, ThermalCORE.

PCM drywall combines gypsum with tiny bits of paraffin wax-based PCM encased in acrylic beads. Referred to as microencapsulated PCM (mPCM), a ScienceDirect.com report on KeAi research said PCM for the lightweight building envelope is the most suitable solution for implementing PCM into buildings. The PCM inside the drywall absorbs heat energy during the day and releases it at night, reducing the need for mechanical cooling and heating.  

A 2019 research paper published by Riga Technical University in Latvia reported that wallboard has been the most common approach for using PCMs in construction.  

 

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Last year, an article in the Journal of Building Engineering stated, “The incorporation of PCM components into building envelopes has proven to have the desired impact of controlling the thermal load, saving energy and maintaining an acceptable thermal comfort.”

Different solutions have been introduced to minimize the heating and cooling loads through the building envelope toward energy-efficient buildings.

Bio-Based Solutions

An online article by Katahdin Cedar Log Homes describes alternate PCMs that can be used in construction. Bio-based PCMs can be made of organic fatty acids, for example a blend of palm and soybean oils, and have a predetermined target melt/solidify temperature. When the room becomes warmer than the target, the bio-based PCM absorbs and stores the energy, changing from a solid to a gel. When the room cools, the PCM slowly releases the stored energy as heat while it changes back to a solid.

Katahdin reports that using PCM technology can enable homeowners to “downsize HVAC units in their homes and save as much as 30% in heating and air conditioning.”

Research and development will continue on different PCMs to expand the temperature ranges where they can be useful, making them even more serviceable in the future for moderating heating and cooling system costs.

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