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BioPCM Thermal Storage Mats

BioPCM is a polyethylene mat with embedded packets of a plant-derived, biodegradable, paraffin phase-change material (PCM)… Read more
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  • Growing and harvesting our building materials would be a great way to move toward a closed-loop system rather than a linear path from extraction to disposal. Doing so holds the promise of true sustainability and regeneration of ecosystems instead of damage to them.

    Unfortunately, biobased materials today can be at least as problematic as any other material. Intensive land use, chemical use, fuel use, nutrient runoff, and other pollution are among the impacts of agriculture; add to that competition between food crops and those used for building materials or fuel. We would like to see sustainable use of biobased materials, but improving practices and figuring out how to assess and document more sustainable practices will take a long time. There is no ready equivalent to FSC for biobased materials that aren’t wood, although certification to “organic” standards or other sustainable agriculture standards can provide guidance in some cases.

    At the same time, we don’t want to exclude biobased products that are typically responsibly sourced just because they don’t have a certification—particularly where they replace more problematic materials. GreenSpec continues to give preference to rapidly renewable alternatives to materials that present greater concerns. Examples of rapidly renewable materials in GreenSpec include linoleum, cork, and textiles such as wool, sisal, and organic cotton.

  • Before specifying efficient heating and cooling equipment, it’s important to do what we can to reduce heating and cooling loads. Insulation is one of the key products to consider here, but because there are so many insulation products on the market, we look for additional benefits. Examples include cellulose insulation with recycled content, mineral wool insulation with no flame retardants, and fiberglass insulation with no formaldehyde binders. Other products in this area are high-performance windows and glazings, products that contribute to building airtight envelopes, products that reduce thermal bridging, and window-retrofit products.

    With products in this area under constant development, we are always refining our approach. For example, as we have learned about insulation products with hazardous flame retardants and blowing agents that have high global warming potential, we have removed those products from GreenSpec, pending manufacturing changes. We encourage building professionals to pressure manufacturers for those changes through specification language and purchasing decisions.

BioPCM is a polyethylene mat with embedded packets of a plant-derived, biodegradable, paraffin phase-change material (PCM). The mat is most commonly installed above ceiling panels or behind drywall in locations with significant temperature swings-, such as commercial kitchens and spaces with significant passive solar heat gain. BioPCM can be ordered with one of four phase-change temperatures: 73°F, 76°F, 79°F, and 84°F. Typically, the lower phase-change temperatures are appropriate for evening out heating loads, while the higher phase-change temperatures are more effective for evening out summertime cooling loads. Different thermal storage capacities are available, as well: M27 (the most popular) provides 27 Btu of latent heat storage capacity per square foot, while M51 provides 51 Btu/ft2, M91 provides 91 Btu/ft2, and M182 provide 182 Btu/ft2 of latent heat storage. By comparison, a square foot of 4-inch-thick concrete slab provides about 90 Btu of heat storage over a 10°F rise in temperature. According to the manufacturer, BioPCM has been tested over 25,000 phase-change cycles without any degradation in performance. Cost is $2–$3/ft2, not including installation.

Thermal storage materials are used in buildings to store heat and reduce temperature cycling, and thus, maintain more even temperatures. By maintaining more constant temperatures and storing heat that is released later in the day (or year), thermal storage materials can improve comfort in a building interior, as well as reduce heating and cooling loads.

A wide range of materials can provide thermal storage, including concrete, brick, tile, stone, plaster, wood, and water. Effectiveness in heat storage is a function of the “heat capacity” of a material and the ability of heat to move into and out of the material. This can be a function of thermal conductivity or, with fluids, convection. These common “thermal mass” materials are all solids or liquids that store and release heat without changing phase.

Some materials can store and release very large amounts of heat as they change phase—absorbing heat as the solid melts and releasing that heat as the liquid freezes. This heat storage relies on the physical principle of “latent heat” capacity. These so-called “phase change materials” (PCMs) can be paraffins, salt hydrates, or eutectic salts. Water also can serve as a PCM, and it is widely used in ice-based Thermal Energy Storage (TES) HVAC systems.

LEED Credits

EAc1: Optimize Energy Performance

EAp2: Minimum Energy Performance

EAp2: Minimum Energy Efficiency Performance

MRc6: Rapidly Renewable Materials

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