- Dec 26, 2012
New Alternatives Promise Increased Thermal Performance in Less Space
By Brad Berton, Contributing Writer
As building science innovators continue devising energy-saving products and methods in the ultimate pursuit of net-zero structures, commercial property executives and their advisors have to select from myriad alternatives for each new development and retrofit venture. And in a large, geologically diverse country like the United States featuring climates from cold and dry to hot and wet, thermal insulation technologies rank among the most logical sources of potential savings.
Indeed, as 2013 approaches, decision-makers considering insulation alternatives are adding some intriguing new-wave products and systems to their lists—including those based on micro-encapsulation of tiny particles boasting remarkable thermal protection properties. These technologies promise to boost thermal performance dramatically while reducing space devoted to insulation materials.
However, with going-in costs of innovative technologies predictably higher than those of traditional insulation materials, pioneering real estate entrepreneurs and their vendors are aiming to demonstrate longer-term viability of advanced technologies such as vacuum insulation panels (VIPs), silica aerogels and phase-change materials (PCMs). Their expectation is that these alternatives can cost-effectively cut energy consumption, especially at peak hours, in turn allowing for downsized HVAC systems. They are also seeking to provide other benefits, such as durability of performance; flexibility to accommodate various construction configurations and materials; adaptability to energy retrofits as well as new construction—not to mention product availability.
As is often the case as innovators transfer technologies to the commercial building sector, many of the new-wave insulation suppliers have initially targeted European markets for their products—and in some cases they have been used effectively in combination with one another as well as separately. If historic patterns hold, costs should continue downward with further product development, supplier consolidation and construction code adoption, making them more attractive to U.S. landlords, predicted Aditya Ranade, senior analyst with Lux Research.
Ranade, who heads Lux’s Sustainable Building Materials service, believes insightful applications of VIP technologies can offer particularly compelling economics to U.S. developers in the relatively short term. PCMs are already demonstrating effectiveness in properties subject to exceptional daytime heat followed by cool nights. While aerogel-based insulation products hold great long-term promise, however, costs will need to fall further before they see widespread adoption domestically.
Vacuum Insulation Panels:
While VIPs at the prevailing development stage cannot boast quite the structural flexibility of aerogel-embedded insulation products, they can offer exceptional thermal performance at a more attractive cost. The latest products often offer R-40 (per inch of thickness) or better thermal protection, compared to just R-4 with many traditional mineral fiber insulation alternatives. As for the physical composition, modern building insulation VIPs’ core glass microfiber matrix materials—most often fumed silica—are encapsulated within a vacuum-sealed enclosure envelope with metal (mostly aluminum or aluminized) skins.
Even though aerogels in certain applications boast superior thermal efficiency, Ranade sees VIPs filled with materials other than silica aerogels—such as polystyrene and polyurethane foam—as probably more promising in the near term in the U.S. commercial building sector.
Indeed, several VIP filler materials can now provide outstanding thermal performance improvements at costs factoring to the relatively short payback periods America’s commercial property executives prefer.
And as a VIP layer can be less than an inch thick, they help keep façade and wall assemblies relatively thin. Not only does this characteristic minimize any intrusion on usable floor space, it also makes VIP use in many energy retrofits viable—even with wood-frame structures, under the right circumstances.
Primary suppliers here in the United States include Dow Corning, ThermoCor and Panasonic.
Some domestically available VIP products remain limited to relatively small panels that are attached individually to wall assemblies with adhesives. One issue is that under typical construction methods, larger panels risk puncture from nails affixing wallboard sheets, seriously degrading thermal performance at the panel edges.
But illustrating progress expected to migrate across the Atlantic, Ranade noted that some European innovators are providing prefabricated cavity-wall assemblies complete with VIP layers. While this alternative cannot match the flexibility of the latest thin aerogel insulation blankets, the far lower costs should make them more economically viable for the time being, Ranade observed.
Installed costs for the most expensive of these pre-assembled VIPs are in the range of roughly $5 to $7 per square foot—certainly not cheap, but with a generally manageable payback period of four years or less.
Durability is an area where VIPs are likely to improve, as it is logically preferable to maintain the initial high performance for decades longer than the 20 to 40 years associated with some of today’s offerings.
Another issue engineers have been striving to resolve is that VIPs can be vulnerable to puncture, deflating the vacuum. But even if the panel gets punctured and the vacuum is lost, Dow Corning estimates (though it does not yet offer a warranty) that its VIPs will typically still offer R-7 protection.
Aerogels’ Long-Term Promise
It is no surprise Ranade and other experts foresee considerable longer-term promise for aerogels, which are billed as the lightest and best insulating solid on Earth and have been used to encase equipment on Mars Explorers. While the new insulating products are flexible, the actual encapsulated aerogel materials are solids composed of particles (derived from gels; hence the name) that are 90 to 99 percent air. These materials, dubbed “frozen smoke,” almost entirely nullify the primary methods of heat transfer: convection, conduction and radiation.
As some of the latest products from key suppliers are sold in insulation blankets rather than stiff panels, aerogels can offer flexibility advantages. And in many cases they are thinner than VIPs, allowing for practical commercial property retrofits through additional layers applied to wall exteriors or interiors.
However, prevailing economics generally make thicker walls insulated with less-expensive material more viable than the thinner aerogel-equipped alternative that can run to $10 per square foot, Ranade said. In fact, he thinks American developers may find aerogels more financially feasible with glazing applications rather than opaque building elements.
Aspen Aerogels and Cabot Corp., both based in Massachusetts, have been the most active developers of aerogel products for domestic building applications.
Phase-Change Materials: Storing Energy
PCMs, which have proven dramatically effective in European office demonstrations, are more of an energy storage technology than a purely thermal barrier material. As CPE detailed last year, the trick behind PCMs is that their encapsulated solutions absorb heat as they liquefy at the desired daytime temperature, then release it when they solidify as temperatures cool at night.
The effect is that room temperatures remain relatively constant until all the PCM melts; only then does the A/C have to engage. As Ranade acknowledged, the financial impact is particularly beneficial where energy costs are higher during peak daytime use periods.
The Lux team feels PCMs today are best suited for climates seeing dramatic changes in temperatures over the course of each day—particularly areas experiencing hot days and cold nights, such as the U.S. Southwest. The math can certainly work in owners’ and occupants’ favor in these markets if peak loads can be reduced 40 or 45 percent, and nighttime heating costs by 60 or 70 percent, Ranade related.
Micronal PCM has also been embedded into plaster, ceiling tiles and aerated concrete. While wallboard and ceiling-tile applications seem the most logical, product developers are embedding PCM capsules into floor tiles, certain roofing materials, attic blankets, moulding—even carpet and paints.
Several American companies are active in developing PCM products targeting the commercial building sector. DuPont’s Energain line uses the PureTemp PCM product from Minnesota-based Entropy Solutions, as does active developer Phase Change Energy Solutions in its Bio-CPM line of insulation products. Fabral Architectural Systems in turn uses Bio-PCM in some of its wall and roof systems. And PCM Innovations, developer of the esBITS product line, continues demonstrating new applications within and beyond the building disciplines.
But PCM costs remain an issue generally, as does fire retardancy for the many products still made with paraffin wax, Ranade noted. Nor have traditional R-value measurement methods incorporated into construction codes kept pace with such variable-state technologies.
But he is confident that sharp American architects and their clients will adopt products that offer considerable energy savings. And that organizations like ASHRAE will remain on top of things in making recommendations for better incorporating such technologies into building codes, he said.