Specification

Three Moisture Benets of Mineral Wool CI
1. Mineral wool ci is vapor permeable
When vapor or moisture-laden air comes in contact with a cold
surface it can condense, (i.e., convert from a gas to a liquid).
Of course, if condensation occurs on a glass of ice water, it’s
fairly harmless. However, if condensation occurs within an
exterior wall assembly, the consequences could be far more
severe. It may lead to mold, mildew, or even structural damage.
Fortunately, assemblies can be designed in such a way that
vapor can exit the wall before it becomes problematic.
Managing vapor ow keeps moisture from collecting on cooler
surfaces, such as the back side of exterior sheathing or interior
drywall or becoming trapped inside the assembly. At roughly 50
perms (per ASTM E96
ii
) Thermaber
®
RainBarrier
®
mineral wool
ci provides a high level of vapor permeance.
In contrast, some foam plastic insulations (e.g., foil-faced
polyisocyanurate) have substantially lower perm ratings and are
classied by building codes as Class 1 vapor retarders (0-0.1
perms). Materials meeting Class 1 are often referred to as vapor
“barriers” because they are considered vapor impermeable.
In most applications, it is important to avoid installing vapor
barriers on both sides of the wall assembly (a.k.a. “double vapor
barriers”) which can trap moisture and reduce the ability of the
wall to dry in at least one direction.
Regardless of the climate zone, permeable mineral wool ci,
combined with appropriate air barriers and vapor retarders, offers
signicant design exibility to AEC professionals while virtually
eliminating the possibility of creating a double vapor barrier
assembly. See Figures 1, 2, and 3.
MINERAL WOOL CI ALLOWS FOR MAXIMUM DESIGN
FLEXIBILITY
Figure 1: Vapor permeable
wall assembly with mineral
wool ci and vapor permeable
air and water barrier system.
Figure 2: Vapor impermeable
wall assembly with mineral
wool ci and vapor impermeable
air and water barrier system.
Figure 3: Vapor impermeable
wall assembly with mineral
wool ci and vapor permeable
air and water barrier system
and interior vapor retarding
membrane.
Scope Statement
When installed in above-grade exterior wall applications, mineral
wool continuous insulation (ci) is uniquely suited to deliver
unmatched re resistance while also managing vapor and liquid
moisture. This bulletin describes three moisture benets of
mineral wool ci and how they enable substantial design exibility
across many construction types and climate zones.
THERMAFIBER
®
RAINBARRIER
®
CI INSULATION
Moisture Performance
ENCLOSURE SOLUTIONS TECHNICAL BULLETIN
2. Mineral wool ci is engineered not to absorb vapor
According to psychometric chart data, published by ASHRAE*,
the higher the temperature, the more moisture the air will hold
before condensation occurs. Conversely, cool air cannot hold
as much moisture, increasing the risk of condensation. As
water is thermally conductive, any moisture in the insulation as
temperatures cool will reduce its R-value thermal performance.
Therefore, it is important that mineral wool ci be engineered not to
absorb water vapor when subjected to high heat and humidity.
Thermaber
®
RainBarrier
®
mineral wool has a minimal sorption
of just 0.03%, even in harsh, hot, and humid environmental
conditions such as those measured by ASTM C1104 (120ºF,
95% humidity for 96 hours). This indicates consistent thermal
performance during the service conditions of the thermal
insulation. Additionally, the sorption property is consistent
throughout the thickness of the mineral wool ci.
*ASHRAE is the American Society of Heating, Refrigerating, and Air-Conditioning Engineers.
3. Mineral wool is compatible with air and water barriers
Owens Corning recommends high-quality air and water barriers
in all applications, installed according to the manufacturer’s
recommendations. Options include, but are not limited to, silyl
terminated polymers, silicones, acrylics, butyls, bitumens,
polyethylenes, and spun-bonded polyolens.
While ASTM E331 – Standard Test Method for Water Penetration
of Exterior Windows, Skylights, Doors, and Curtain Walls by
Uniform Static Air Pressure Difference – is not typically performed
with insulation in place, Owens Corning completed such an
assessment.
Thermaber
®
RainBarrier
®
45 mineral wool was secured over an
STP Air & Water Barrier alongside FOAMULAR
®
XPS insulation
with no difference in performance. See Figures 5, 6, and 7. The test
was conducted using assemblies and found:
• No leaks were reported at the 15-minute threshold required to
pass code criteria
• No leaks were reported after two hours of excessive, extended
exposure
Such testing conditions should be considered extreme as ci
should be protected by veneer which was not in place for testing.
vi
Repetitive results in this test demonstrate that the assembly was
compatible and fasteners penetrating the mineral wool and air
barrier did not cause failure.
MINERAL WOOL CI WAS INSTALLED OVER AN AIR
BARRIER IN AIR AND WATER BARRIER TESTING
Figure 5: Partial installation
of mineral wool ci over an air
and water barrier system
Figure 6: Mineral wool ci
over an air and water barrier
system which was subjected
to air and water testing
Figure 7: Mineral wool ci over
an air and water barrier system
undergoing ASTM E331 testing