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From below
the ground . . . up. . . .
XPS is very suitable for use.
XPS is often used in foundations because of its high, stable,
long-term R-value of 5 per inch and its excellent water resistant
properties. It is also unaffected by common soil acids, mildew
and fungus growth, decay or corrosion — properties that
make it ideal for long-term durability.
Extruded
polystyrene foam (XPS) insulation is most commonly-used below-grade
in poured concrete, or concrete block foundation systems.
Foundations play an important role in keeping a building comfortable,
moisture-resistant, and structurally sound.
Learn how XPS can help.
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Insulation that comes in
contact with the soil is subjected to severe conditions,
including long-term exposure to water, high soil humidity
and freeze thaw action. These environmental factors can
diminish an insulation’s effectiveness. Therefore,
insulation in contact with the ground should be inert
to the action of soil and water such that its insulating
properties are not diminished due to this exposure. XPS
insulation is ideal for below-grade applications due to
its high moisture resistance and long-term insulating
performance.
In "slab-on-grade" applications, shown to the left here, XPS
boards are applied vertically to the inside of the foundation
wall. Additionally, XPS can be used to insulate beneath
the floor slab. |
Freezing has little or no harmful effect on
insulation that remains dry, or rather, does not absorb moisture
from the surroundings such as XPS. Conversely, insulation
that gets wet does not perform as well. This is an important
consideration when specifying an insulating material where
freeze-thaw cycles are common. Weather data demonstrate that
many locations in North America will experience several hundred
freeze thaw cycles over a 10 to 20 year period. Independent
studies demonstrate that only XPS insulation is suitable for
use in wet, below grade environments where freeze-thaw cycles
are typical.
There are several advantages to insulating
the exterior surface of foundation walls. The block or concrete
wall insulated on the exterior surface is not subjected to
large temperature differences and so will not act as a thermal
bridge. Block walls insulated on the exterior undergo less
air convection in block cavities. At nearly room temperature,
the basement walls act as a heat reservoir, buffering interior
temperature fluctuations. In some instances, adfreezing forces
are prevented from acting directly on the basement wall.
In "slab-on-grade" applications,
XPS boards are applied vertically to the inside of the foundation
wall. Additionally, XPS can be used to insulate beneath the
floor slab.
XPS insulation is available with varying degrees of compressive
resistance from 25 psi to 100 psi. The higher compressive
strength insulation should be considered in applications subjected
to high loading, i.e., mechanical equipment, etc.
XPS is durable and versatile, thus it stands
up to the rigors of job-site handling and is available in
a variety of sizes. XPS insulation for below grade applications
is typically provided in standard 2’ or 4’ widths
by 8’ lengths and in thicknesses ranging from 1”
to 4”. XPS insulation is easily cut on the job-site
to needed sizes by scoring with any common knife and snapping.
—CASE
STUDY—
Silver Valley Condominimum
Complex, Munroe Falls, Ohio
Insulation for both above- and below-grade
applications saved installation time and money for the builder
of Silver Valley Condominium Complex in Munroe Falls, Ohio.
Set among 50 acres of land with an 11-acre lake, the complex
consists of 200 two-story condominiums. “One of the
main advantages of using extruded polystyrene insulation (XPS)
was its versatility,” said Mr. Jim Fox, superintendent
of Botnick Building Company, builders of the Silver Valley
Condominiums. “Once it is on the job, we can use it
virtually everywhere.”
XPS TYPE X as listed in ASTM C 578 2002 is being used at Silver
Valley in the foundations, the vaulted ceilings, and behind
the entire envelope of the construction. XPS is also being
applied in non-living quarters, such as around the garage
area and the gable end walls of the attic.
In the foundation, XPS was installed vertically against the
concrete block foundation and was held in place by the backfill.
A plastic membrane was then placed onto the dirt floor, followed
by XPS, and then a 4” slab of poured concrete. The insulation
provides the benefits of a thermal break between the soil
temperature and the inside temperature. In the condos that
have a full basement, they installed the XPS TYPE X as listed
in ASTM C 578 2002 on the outside of the concrete block, followed
by backfill.
XPS is often used in foundations because of its high R-value
of 5 per inch of material and its excellent water resistant
properties. It is also unaffected by common soil acids, mildew
and fungus growth, decay or corrosion — properties that
make it ideal for long term durability.
In addition, XPS TYPE X as listed in ASTM C 578 2002 was installed
in the walls of the Silver Valley project. “We were
able to erect the walls without pre-insulating,” explained
Mr. Fox. “We used tongue and groove XPS, starting at
the slab and completely encompassing all aspects of the entire
exterior. By running it in this manner, it takes less product.
We found approximately 10% less waste compared to other 4’
x 8’ insulation products, and the tongue and groove
edges fit tightly and did not break at the stud. There is
less waste on the windows and doors,” he continued.
“XPS was also installed above ground, in the garage
and attic area, particularly in places where stucco walls
were used. Other insulations, like mineral impregnated fiber-board,
will not allow the stucco to adhere as well. The fiber-board
draws the water out of the stucco, causing it to dry and crack.
Because of XPS’s excellent water resistance, no protection
is required underneath the stucco application. We also eliminated
the necessity for a paper liner that is needed when using
other insulations. We simply apply the stucco after the lath,
this saves time and material,” stated Mr. Fox.
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