Reducing Costs While Meeting Code-Required Continuous Insulation
Among commercial and institutional buildings in the U.S., hospitals have the highest energy use intensity (EUI) level, ranking a close second to supermarkets, per U.S. Dept. of Energy (DOE) data. Because they operate 24/7 and are loaded with energy-hungry equipment, it’s no surprise hospitals use huge amounts of energy per square foot. On the other end of the spectrum, K-12 schools rank low for EUI. Even so, facility professionals in both hospitals and schools must find ways to reduce heating and cooling energy use – either to save on operating costs or to meet building codes.
Code Requirements for Continuous Insulation (CI)
Hospital and school building professionals are acutely aware that building codes related to energy use are becoming increasingly stringent. Over the years, these codes have had a dramatic impact on reducing energy consumption. For example, the EUI of commercial buildings is nearly 50 percent less under ASHRAE 90.1-2013 than it was under ASHRAE 90A-1980, according to DOE. That trend has accelerated over time, with EUI dropping especially sharply with the adoption of the 2001 and 2007 versions of ASHRAE 90.1.
Since 2007, ASHRAE 90.1 has required continuous insulation (CI) in most U.S. climate zones. Sixteen states have mandatory statewide commercial energy codes that meet or exceed that standard. California has gone even farther with its Title 24 Energy Efficiency Standards, which call for all new commercial buildings in the state to be zero net energy by 2030.
As a result of all these changes, architects and contractors have had to pay additional attention to creating well-insulated building envelopes.
While it is a somewhat self-explanatory term, continuous insulation is defined in ASHRAE 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, as:
“Insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope.”
Structural framing members, such as studs and joists – whether wood or steel – conduct heat much more readily than does building insulation, so are a substantial path for heat loss. As these members account for a high portion of a wall’s area, the effective R-value of the wall assembly is well below the nominal R-value of insulation installed between the members. CI is explicitly intended to reduce this thermal bridging.
While ASHRAE 90.1 does not specifically call for underslab insulation, project teams interested in high-performance envelopes often also include a continuous layer of rigid foam under floor slabs.
Building teams have a range of options for providing CI to meet code requirements. The most commonly used among these are rigid foam products:
- Expanded polystyrene (EPS)
- Graphite polystyrene (GPS)
- Extruded polystyrene (XPS)
- Polyisocyanurate (polyiso)
- Structural insulated panels (SIPs)
EPS and GPS
Among rigid foam insulations, EPS and GPS have the highest R-value per dollar, which makes them well suited for cost-effective continuous insulation. (GPS is graphite-enhanced EPS to provide higher R-values.) Unlike other rigid foam insulations, EPS and GPS retain their R-values throughout their time in service. EPS is one of the most versatile rigid insulations because it can be used anywhere in the building envelope – roof, walls, floors and even below grade.
Mostly used in walls or below grade applications, XPS is mid-range in price between EPS and polyiso. Although XPS is slow to absorb moisture, it is also slow to release it, which can reduce the insulation’s effective R-value as it retains moisture over time.
Historically polyiso was used in roof assemblies, although some manufacturers now offer wall insulation. As with XPS, polyiso R-values degrade over time as the thermal-enhancing blowing agents used to make them mix with air to reduce the long-term R-value.
By integrating a building’s structural components and insulation in one unit and coming in large wall and roof sections, SIPs have far fewer gaps to seal than other structural systems, and provide continuous insulation and reduced thermal bridging. R-values depend on the panel thickness and type of rigid foam insulation used, but SIPs can help reduce heating and cooling energy use up to 60 percent compared to other construction methods. These products commonly use EPS insulation, while GPS options also are now available.
Ways to Reduce CI Labor and Material Costs
Rigid foam insulation manufacturers offer a number of product options that help building teams reduce their continuous insulation labor and material costs. One example is rigid foam in “fanfold” bundles, such as Insulfoam’s R-Tech FF, made-up of 25 two-foot by four-foot faced EPS panels, with each panel attached to its neighbor along one side. The bundles weigh less than 11 pounds each, so it is easy for one person to carry two bundles, which easily unfold to cover up to 200 square feet per bundle.
EPS fanfold bundles may require fewer fasteners than other exterior wall insulations, and require about 60 percent fewer man-hours to install than working with individual insulation sheets.
SIPs provide another way to simplify CI. The panels come in large sections (up to 8×24 feet) labeled for ready installation according to a coded plan. Builders can thus construct entire walls and roofs in a matter of hours, instead of days or weeks.
A number of other rigid foam insulation product configurations exist for simplifying and reducing costs of CI; check with the manufacturer for details.
Although EUI generally is high for hospitals, with attention to the building envelope, you can help ensure the facilities you are involved with are as energy efficient as possible. A key step in that is via continuous insulation, as part of a high-performance building envelope.
Michael McAuley is president of Insulfoam. McAuley has more than 20 years of experience in building material sales and production management, including 14 years at Insulfoam’s sister company, Versico Roofing Systems, as the National Sales Manager and General Manager. Visit www.insulfoam.com to learn more.