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By John A. D’Annunzio
Windows & Exterior Walls Article Use Policy
Implementing various methods to decrease (or eliminate) heat loss at walls and roofs is another important way to boost overall building performance.
The addition of sprayed polyurethane foam (SPF) to walls can increase energy efficiency. SPF is most associated with roofs and specialty industrial applications, so many facility managers may not know the product has a long, successful track record in building enclosures.
In contrast to conventional board insulations, SPF can be applied in the tight, hard—to—reach areas. For example, full application can be achieved at stud walls with a significant amount of conduit running through it or at ceilings of mechanical rooms. The full bond of the material eliminates air gaps and voids that can contribute to thermal loss.
SPF provides a high R—value — 2.5 inches has a rating of R—17 — and is as much as 40 percent higher than other insulating materials. The product has excellent adhesion capabilities and can be successfully applied over all types of substrates, including gypsum, plywood, masonry block, and even glass.
In addition to boosting energy efficiency, SPF provides an excellent air barrier that meets the latest code requirements and serves as a vapor barrier preventing mold growth.
Roofs are the largest building envelope component and thus have the potential to provide significant savings. Roof systems impact energy efficiency through thermal capacity, reflectivity, and emissivity.
You achieve thermal capacity by installing an insulation system with high R-value. In commercial, low-slope roof systems, the insulation is typically a rigid board applied above the deck. High thermal value insulation will reduce heat loss in the winter months, which decreases heating costs.
Roof insulation regulations have recently changed with adoption of the ANSI/ASHRAE 189.1 standard for the Design of High Performance Green Buildings to the International Building Code. This regulation is an update from ANSI/ASHRAE 90.1, which was modified in 2007. The new regulation provides minimum requirements for high—performance buildings. The goal of the new standard is to obtain 30 percent efficiency over the 2007 standard. The standard covers all new buildings and new systems in existing buildings except low—rise residential buildings.
This regulation now provides the requirements for roof insulation R—values for every region of the country. Prior to this regulation there were no code requirements for minimum roof R—values. The regulation also changes the formulation of how roof R—values are determined. Prior to this regulation, roof R—values were based on the entire roof system — deck, air film, underlayments, insulation, membrane, and surfacing. The ASHRAE 189 standard defines the R—value as only the insulation system (i.e., bottom board and cover board). It also defines R—value based on the material’s long—term thermal value (LTTR) as opposed to the initial R—value at manufacturing. Insulation manufacturers provide LTTR values for all of their materials based on their thickness.
One design note: The current LTTR values are achieved through the use of thicker insulations, which may require raising flashing heights at walls and penetrations.
Weather-Proofed Windows and Energy Efficiency
Target Heat Loss at Walls, Roofs to Boost Building Performance
Materials on Roof Surface Can Build Energy Efficiency