Stricter Energy Codes
The 2012 and 2015 versions of the International Energy Conservation Code include climate zone–specific requirements for insulating and sealing commercial and residential buildings. Though these two versions are largely identical, they depart significantly from the 2009 code with regards to wall-cavity insulation. For metal- or wood-framed walls, projects must now achieve a minimal thermal resistance of R-13 in the cavity and have a continuous exterior insulation layer with a minimum R-value of 3.8 in the warmest climate zones to 17.5 in the coldest, says Ryan Meres, a senior code-compliance specialist at the Institute for Market Transformation, a Washington, D.C.–based nonprofit. Alternatively, wood-framed projects can opt to have just an R-20 cavity.
“Cavity insulation insulates between the framing members, but continuous insulation insulates over [them], preventing thermal bridging through the much lower R-value framing material,” Meres explains. While fiberglass batts, cellulose, and spray foams are common for the cavity, rigid foam board is typically used for the continuous portion, a pairing that has architects and engineers reworking the math on their approach to wall systems.
“We want these continuous insulations, but in their use we’re violating the rules we were taught,” says Lucas Hamilton, a building-science applications manager at Malvern, Pa.–based building-products manufacturer CertainTeed. Adding continuous insulation to the outside of the wall cavity changes how air and water move through it, potentially trapping moisture in the wall and requiring versatile air and vapor barriers to keep the cavity dry as temperature and humidity change year-round.
The change is also requiring new kinds of product testing. Typically air and water barriers are combustible, as is continuous insulation, which lately is specified often as plastic foam, says Herbert Slone, manager of commercial building systems at Toledo, Ohio–based building-products maker Owens Corning. As a result, he continues, “you have this dichotomy where the code says these types [of installations] need non-combustible walls but the energy code says to wrap those in materials that are combustible.” One result is the National Fire Protection Association’s standard 285, which now tests new combustible materials for use in typically non-combustible wall applications.
Insulation’s ingredients are also becoming more efficient. Spray-foam makers, such as Canadian manufacturer Icynene, are adding low-VOC insulation to their lineups to cut re-occupancy times down to a few hours following installation. The addition of compatible through-wall flashing and sealant details to create water-resistive barriers are allowing spray foam to be used as continuous insulation, says Paul Duffy, vice president of engineering for the company. According to Freedonia, fiberglass has long led the industry as the prominent insulation type, with foamed plastic (both spray and rigid) not too far behind it. Foamed plastic is expected to overtake fiberglass within a decade as some of the largest-volume producers in the category—Owens Corning, Dow, and Johns Manville among them—report roughly equal sales of the two materials, the research firm found.
Other improvements include the addition of graphite to plastic-foam mixes, which multinational chemical producer BASF found can cut heat transfer by up to roughly 20 percent. Mineral wool, made from various types of slag or stone, is projected to double in production over the next decade in part due to its ability to insulate in hot and cold temperatures, Freedonia reports, as well as its sound-abatement and fire-prevention qualities, says Michael Bennetti, who manages commercial sales at Canada-based mineral-wool insulation manufacturer Roxul.
More insulation products made with plant-based materials like waste wood, cork, and kenaf (a cousin of hemp) are on the horizon, reports Freedonia as well as a July report in the journal Sustainable Materials and Technologies. The latter recommends that these alternatives be explored particularly in developing countries with large volumes of agricultural and industrial by-products.
Manufacturers are also helping project teams understand the complexities of the new wall-system requirements by packaging insulation, cladding, and weather barriers into wall assemblies that can be specified like one product. Owens Corning’s CavityComplete (shown left), BASF’s HP+, and Dow’s Thermax wall systems, for example, integrate multiple products and can be customized to meet a specific R-value.
“You’d never buy a car by ordering your brakes from Ford and your chassis from General Motors," Hamilton says, "yet we do that with houses [and other buildings] all the time and expect them to work. If you can work out the wall system in advance and provide that packaged performance, that’s a goal we see everyone shooting for.”