Continuous Insulation keeps buildings energy
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
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
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
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.
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
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
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
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.