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Q. What insulation options are available
with shotcrete wall systems?
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A typical prefabricated shotcrete panel
showing insulation and reinforcement. Image courtesy of M2
(Emmedue),
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A. Typical shotcrete wall assemblies
feature a core of insulation material sandwiched between two layers
of reinforced concrete. The prefabricated panels include a layer
of expanded polystyrene (EPS) insulation board between two welded
wire faces. The thickness of the insulation core can vary, but is
most commonly 4 in.
Some manufacturers offer a variety of thicknesses and densities
of foam. In colder climates, thicker insulation (or higher density)
is often required. One midwest manufacturer incorporates 7-1/4-in.
of EPS insulation within the panels to provide high thermal performance
for cold climates (northern applications).
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| This spray-applied insulation is placed between
furring strips before interior drywall is placed. Photo courtesy
of Bond
Building Systems, Inc. |
Some shotcrete systems do not incorporate the insulation material
within the shotcrete panels. When those systems are used in climates
where insulation is required, furring strips are anchored to either
the interior or exterior face of the completed shotcrete wall assembly.
Rigid boards of EPS or extruded polystyrene (XPS), spray applied insulation,
or fiberglass batts can then be installed between the furring. On
interior applications, a layer of drywall over the insulation completes
the installation. Where insulation is installed on the exterior, a
weather resistant barrier is placed outboard of the furring strips
before attaching the exterior finish material. Common exterior finishes
include stucco, siding, brick, or manufactured stone. The benefit
of placing insulation toward the exterior is that the concrete is
closer to the interior where it may have a greater thermal mass effect.
For the shotcrete systems that contain integral foam (a core), adding
interior or exterior supplemental insulation further improves their
thermal performance.
Table 1 shows a comparison of the thermal properties of the commonly
available insulation products that could be incorporated within
a shotcrete wall assembly.
| Table 1: Approximate R-values
of Common Insulation Materials |
| |
R-value per inch |
Density lbs/cu ft |
| EPS |
3.6 - 5.0 |
0.8 - 2.0 |
| XPS |
5.0 |
1.5 |
| Cellulose |
3.2 - 3.7 |
2.2 - 3.0 |
| Open cell spray foam |
3.6 |
0.5 |
| Closed cell spray foam |
6.5 |
2.0 |
| Fiberglass batt |
3.1 - 4.0 |
0.6 - 1.2 |
 Donn
C. Thompson, AIA, CGP, LEEP AP is Director
of Low Rise Buildings for the Portland Cement Association (PCA).
A licensed architect, Donn has more than 20 years experience in
commercial and residential construction.
More
on Donn Thompson.
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