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Efficient Insulation

Marcy Marro, Editor, Posted 08/01/2017

Continuous Insulation keeps buildings energy efficient

Continuous Insulation keeps buildings energy efficient

The use of continuous insulation (CI) has been growing in recent years and is a requirement in many energy codes to achieve higher thermal efficiency standards in all types of buildings. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 90.1, Energy Standard for Building Except Low-rise Residential Buildings, defines CI as "insulation that is uncompressed and continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope."

In simpler terms, Keith D. Boyer, PE, director of architectural wall technology at Moon Township, Pa.-based CENTRIA, says continuous insulation is an efficient use of insulation that eliminates severe thermal bridges that can greatly affect the overall thermal performance of the insulation. "Thermal bridges, like full-depth Z's, can decrease the effectiveness of the insulation," he explains. "Another example of thermal shorts in insulation is the use of insulation in the cavity of metal studs. Per ASHRAE 90.1 table A9.2-2, tested insulation values like R-21 glass fiber insulation performs only to an R-7.4 when used in the cavity of 6-inch metal studs 16 inches on-center."

Thermal bridging is caused when anything penetrates the insulation. This includes metal studs, mechanical fasteners, cladding fastening systems, floor support beams, etc. Eliminating thermal breaks leads to reduced energy consumption of the building.

 

continuous insulation keeps buildings energy efficientCompliance Options

In addition to ASHRAE 90.1, most energy codes, such as the International Energy Conservation Code (IECC), require increased R-values for commercial buildings. The 2010 update of ASHRAE 90.1 cut accepted building energy use by 30 percent over 2004, and recommends CI as a requirement in all climate zones, along with increased R-value requirements.

There are two options for compliance: the "Minimum Rated R-Values," method or the "Maximum U-Factor Assembly" method. Both establish the same functional amount of wall insulation in a given climate zone, regardless of which option is used.

"All codes and standards are U-Value performance-based," explains Bill Beals, district manager at Therm-All Inc., North Olmsted, Ohio. "The fiberglass and continuous insulation tables are just assembly options. The U-Factor alternative allows a designer to use any system that is tested per the ASTM C518 or ASTM C1363 hot box test, which means you can build a complete assembly with fiberglass and any other products you choose, so long as the result is a U-value equal to or better than code. This allows many options outside the standard assembly descriptions. It also allows for innovation."

Boyer adds that by testing a building envelope assembly in a thermal test such as the ASTM C1363 can account for any subtle thermal shorts or heat flow through the wall assembly. "In these assemblies, there is no reference to CI," he says.

For the "Minimum Rated R-Values," there are prescriptive tables for each climate zone, with CI listed for the different assemblies. Many times, the CI is combined with insulation in the stud cavities. For example, Boyer cites that for Climate Zone 5 for steel-framed walls above-grade for nonresidential construction, it is listed as "R-13 + R-10 c.i." The R-13 is insulation in the stud cavity, which Boyer notes, per ASHRAE table A9.2-2, is only R-6 with 16 inches metal stud spacing, and the R-10 c.i. is the continuous insulation, which is typically located on the outside of the stud frame.

 

continuous insulation keeps buildings energy efficientInstalling CI

In assemblies using CI, Boyer notes that there are several additional components that create air and water barriers, as well as vapor retarders. "In addition to avoiding the thermal bridges, care must be taken not to allow air or water to get behind the insulation," he explains. "Should this happen, the effectiveness will be compromised."

According to Beals, a 6-inch metal stud wall allows for a relatively easy application of CI, while a metal building wall may be a little more difficult. "Buildings are designed to specific wind and loading requirements," he explains. "When foam board is installed between wall girts and roof panels, designs can become compromised. Thus, building manufacturers need to know whether or not the CI will be installed between the exterior side of framing and sheeting. Additionally, exposure becomes a problem. If the continuous insulation is going to be exposed to the interior side of the building, the fire and smoke ratings of the product need to be addressed."

Beals goes on to say that if a metal building wall is using CI, and the fire and smoke ratings have been addressed, then meeting code requirements is a little simpler. "To be in compliance under the U-Factor Alternative, we often see metal building walls use a combination of R-13 plus R-13 CI," he says. "This means that R-13 fiberglass is installed with the exterior wall panel and R-13 CI is installed on the interior side of the girts."

Boyer says foam plastic insulations offer some of the highest insulation values available and most easily answer the definition of CI. "These materials have compressive strength, and sub-frames can be applied to the outer surface and fastened through the insulation-thus meeting the definition of CI," he explains. "Many times, metal-faced foam will have to be used to meet the fire protocols as stated in Chapter 26 of the IBC."

With board-type insulation, Boyer notes that a tape or membrane is typically applied over it to seal the joints. "Also," he says, "the location of the vapor barrier on these types of assemblies is dependent on the climate and building interior and is critical to prevent potential moisture entrapment."

Insulated Metal Panels

Combining multiple components-water, air, vapor and thermal barriers-insulated metal panels (IMPs) fulfill the "Maximum U-Factor Assembly" method for compliance. Testing for IMPs is based on either ASTM 1363 or C518, and generates an overall U-value for each panel style. "The generated U-value is often very close to the stated R-value of the panel," explains Bill Beals, district manager at Therm-All Inc., North Olmsted, Ohio, "but some narrow styles have in-place R-values that are a little less due to extra seams. Insulated metal panels have seen significant growth in our industry and are a good option for meeting many of the code requirements."

Don Ross, president of D.W. Ross Insulation, Cleveland, explains that continuous line insulated metal panels allow for extremely energy-efficient building envelopes that can vary from 2 inches at R-16 up to 6 inches and R-48 insulated core options. "Optimally, in commercial and industrial building walls, we like to see a minimum of R-16 or 2 inches," he says. "On the roof panel, we like to see a minimum of R-32 or 4 inches. In residential applications, we like to see an R-48 on the roofs."

Continuous line insulated metal panels are used for both wall and roof applications, and are installed over steel framing or wood framed structures. "There are specific fastening methods and these can be illustrated with factory shop drawings or communicated and details so the panels are installed to meet the building code criteria," Ross explains.

Proper equipment and rigging is necessary when installing continuous line insulated panels. "The challenge is getting accustomed to working with the modular, pre-engineered panel," Ross says. "It will save time in the construction schedule. The interior side of the insulated panel is already pre-finished. This eliminates the need for conventional installation and a metal interior panel having to be installed over conventional insulation."

To preserve the continuous insulation application, Ross notes that there are female longitudinal joints that can either be factory pre-caulked or field-applied caulked just prior to installing in place, which creates a vapor barrier and eliminates any air infiltration through the continuous line panel system.

And, in terms of thermal bridging, Ross says it is important at the wall and roof junctures, base plate detail and vertical wall to wall intersect. "Not only do the thermal breaks need to be installed correctly, but an effective vapor barrier as well as spray foam urethane needs to be implemented-installed to fill any voids at these intersects," he says.

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