WEB EXCLUSIVE: "Ci" And Facility Energy Efficiency
The Web Exclusive comes from Doug Todd, North America market manager, Dow Building Solutions.
Continuous insulation—”ci” for short—is a term facility managers will be hearing more often in the planning stages of their new construction and major renovation projects. Like a coat that provides greater warmth when it’s zipped rather than not, “ci” covers the entire wall surround—not just the cavity spaces between the framing studs. “Ci” is a proven energy saver that is gaining attention across the U.S.
For at least 20 years ASHRAE has mandated “ci” for the coldest U.S. climate zones—places like northern North Dakota, northern Wisconsin, and Alaska. Now, changes to the ASHRAE 90.1-2007 Energy Efficiency Standard make “ci” a prescriptive requirement for above-grade, steel frame commercial construction in six out of eight climate zones, which is essentially all of the U.S. except for its southernmost points. See this link for climate zone breakdown.
In terms of LEED certification, in version 3.0 of the LEED rating system, the Energy and Atmosphere (EA) credit category now uses ASHRAE 90.1-2007 as its baseline. And the range of points for EA Credit 1 has increased from 1-10 to 1-19.
There are wall systems on the market that make it easier to integrate “ci” into building plans. These types of systems are gaining traction across climate zones as architects, contractors, and facility managers discover that they can improve thermal efficiency with less labor and cost than traditional gypsum wall systems or alternative “ci” components.
Heat transfer through steel studs can decrease effective R-value of cavity insulation by more than 50% (see Figure 1). If not addressed, the issue can overwork a facility’s HVAC system, requiring much more energy to heat and cool than it should.
Energy loss is most pronounced in wall systems that place batt insulation on the interior wall between the studs and use un-insulated sheathing on the exterior, such as gypsum board. This configuration, while very common in the vast majority of commercial structures, encourages heat transfer through steel studs (see Figure 2). Left unprotected by insulation, the building’s steel frame turns into a kind of thermal super highway, where indoor heat moves out during winter and outdoor heat moves in during summer.
Heat transfer through steel framing also encourages condensation within the cavity. The moisture build up further reduces the effectiveness of the batt insulation and if it does not dry out, can lead to mold and mildew, as well as material degradation.
Adding thicker insulation between the studs will not significantly improve thermal performance. In fact, it’s physically impossible to design an R-19 steel stud wall system with R-19 rated batt insulation alone.
A Different Approach
Wall systems that integrate “ci” represent a fundamentally different approach to steel frame wall construction. Those that combine “ci,” an air barrier and moisture-resistant barrier in a single-source solution can help to reduce materials and labor costs, as well as installation time.
One system, the THERMAX Wall System from Dow Building Solutions, integrates an acrylic-coated polyisocyanurate foam sheathing, flashing and spray polyurethane foam in a single-source solution. Lightweight, rigid foam insulation panels installed outboard of the stud deliver a high level of heat resistance to the entire envelope—not just between the studs. The effect is to shut down the thermal superhighway of heat transfer. The sheathing’s facer protects against moisture intrusion. Seams, windows, doors and other thru-wall penetrations are taped with flashing for further moisture protection. Sealing the interior wall cavity with spray polyurethane foam effectively reduces air infiltration through building gaps, cracks and pinholes that can account for up to 38% of heat transfer in a typical building.
Whether it’s for new construction or a major re-model, the choice of insulation affects a facility’s energy efficiency long after construction ends. By combining “ci” with air sealing, these types of wall systems go beyond the ASHRAE 90.1 standard and moves closer to the ultimate goal of carbon neutrality in building operation.
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