Below is for informational purposes. We do not sell Foam
or Foam Board Insulation.
Foam and Foam Board Insulation
Even though many foam insulation
products are more expensive than other types of insulating materials, such as
fiberglass, cellulose, etc., they are commonly used in buildings where there are
space limitations or where very high R-values are desirable. Foam insulation
R-values range from R-4 to R-8 per inch of thickness (2.54 cm), which is 2 to 3
times greater than most other insulating materials of the same thickness. Also,
if the installation is carefully installed, foam insulation may control air
infiltration more effectively than other types of insulation.
Several variables affect the
installed R-value of foam insulation, including: the initial density of the
foam; the blowing gas used (CFC, HCFC, CO2, air, or a number of other gases);
how the foam insulation is handled (dents and chips adversely effect the
R-value); the type of facing (if any) used; and the conditions in which the foam
Foam insulation is often made with
one of three materials: molded expanded polystyrene (MEPS), extruded expanded
polystyrene (XEPS) or polyurethane, polyisocyanurate, or a related chemical
mixture. Some are installed as a liquid while other types come as factory made
panels or "foam board."
Liquid foam insulation can be
applied from small spray containers as a liquid or in larger quantities as a
pressure sprayed (foamed-in-place) product. Both types expand and harden as the
chemical mixture cures. It also conforms to the shape of the cavity to fill and
seal it thoroughly. This type is often used in new construction.
There are also slow curing liquid
foams that are designed to flow over obstructions before it expands and cures.
This type is often used for empty wall cavities in existing buildings. There are
also liquid foam materials that are poured from a container.
Both are generally urethane foams.
Latex and organic based foams are available too. Be aware that these
alternatives do not have as high an R-value as a urethane-based products.
Molded Expanded Polystyrene (MEPS)
MEPS is a closed-cell material that
can be molded into many everyday items, such as coffee cups and shipping
materials, or into large sheets as construction insulation. This material is
commonly known as "beadboard," and it has an R-value of about 4 per
inch of thickness [2.54 cm].
To make beadboard, loose, unexpanded
polystyrene beads containing liquid pentane are mixed with a blowing agent and
poured into an enclosed container. The mixture is then heated to expand the
beads many times their original size. The beads are then injected into a mold
and under more heat and pressure expand to become foam blocks that are then
shaped as required.
The physical properties of MEPS vary
with the type of bead used, but the density of the board is usually one pound
per cubic foot (16.3 kilograms per cubic meter.) Beadboard is manufactured at
various densities, depending on the application. Beadboard for roofing materials
has to be dense enough to walk on without damage. Wall insulation boards are
several times less dense than roof boards. R-values range from 3.8 to 4.4 per
inch (2.54 cm) of thickness. Since spaces between the foam beads can absorb
water, a vapor diffusion retarder is necessary if water transmission through the
insulation might present a problem for the user.
MEPS foams are also available as
small beads of foam too. This type is often used as a pouring insulation for
concrete blocks or other hollow wall cavities. However, be aware that poured
beads are extremely light-weight and take a static electric charge very easily.
They are notoriously difficult to control and any wind at all often results in
the beads flying all over the place. Also, if there is ever a hole in the wall
the foam beads will continue to fall out of the hole until the wall is almost
empty of beads.
Extruded Expanded Polystyrene (XEPS)
Extruded expanded polystyrene (XEPS)
is a closed-cell foam insulation similar to MEPS. To make it, the polystyrene
pellets are mixed with various chemicals to liquefy them. A blowing agent is
then injected into the mixture, forming gas bubbles. The foaming, thick liquid
is then forced through a shaping die. When cooled, the panel is cut as required.
Foam densities are typically 1.5 pounds per cubic foot (0.21 kilograms per cubic
XEPS is more expensive than MEPS,
and like MEPS the R-value depends upon the density of the material. Generally,
it's about R-5 per inch. It is also much more consistent in density and has a
higher compressive strength than MEPS, making it better suited for use on roofs
or for wall panels. Extruded polystyrene also has excellent resistance to
Both MEPS an XEPS are often used as
the insulation for Structural Insulating Panels (SIPs) and as Insulating
Concrete Forms (ICFs.)
Polyurethane and polyisocyanurate
are both closed-cell foams that contain a low-conductivity gas in the cells
(usually one of the HCFC or CFC gases.) The high thermal resistance of the gas
gives these foams an R-value of between R-7 and R-8 per inch.
Both types are available as a liquid
spray, poured foam and also as rigid boards. They can also be made into
laminated panels with a variety of facings. Foamed-in-place applications are
usually cheaper than installing foam boards and perform better since it molds
itself to all of the surfaces perfectly. However, be sure you use a contractor
with plenty of experience with spray foam installations.
Over time, the R-value of the foam
drops as some of the gas escapes and air replaces it. This phenomenon is known
as thermal drift. When manufactured, the initial R-value is roughly R-9 per
inch. Experimental data on this type of foam indicates that most thermal drift
occurs within the first two years after manufacture and slowly decreases until
it stabilizes at about R-7 per inch. It then remains unchanged unless the foam
Foil and plastic facings on these
foam panels help to slow the escape of gas from the cell structure. Testing
suggests that the stabilized R-value of rigid foam with metal foil facings
remains unchanged after 10 years. The reflective foil, if installed correctly,
can also act as a radiant barrier (another type of insulation) that adds about
R-2 to the insulating assembly. Panels with foil facings have stabilized
R-values of 7.1 to 8.7 per inch.
Common Applications of Foam
Spray foam and foam boards can be
used to insulate almost anything, including: roofs, walls, foundations, entry
and overhead garage doors, pipes and tanks, under basement slabs, or over a
slab-on-grade floor. Foam insulation sprayed or placed in wall and floor
cavities both insulates and offers some degree of soundproofing.
Protect all types of foam insulation
from direct sunlight. Over time, the sun's ultraviolet rays can damage them. For
roofs this is generally done by applying a coating such as tar, acrylic,
silicone or rubberized paint. You can also cover the foam with a rubber or
plastic membrane or a layer of asphalt and roofing felt. Make certain you are
using compatible products. The solvents in some coatings dissolve certain
There are several ways to
incorporate foam insulation in concrete or masonry walls: pouring loose foam
beads into masonry blocks; injecting/ pouring liquid foam into the hollow block
cores; manufacturing concrete blocks to accommodate rigid foam inserts; as
lightweight concrete blocks that have polystyrene beads in the concrete mixture;
and as rigid foam insulation inside a cast-in-place wall. There are also
interlocking rigid foam panels and blocks that serve as permanent forms for
concrete walls and foundations. These are commonly known as Insulating Concrete
Potential Moisture Problems
In cold weather, warm inside air
containing water vapor can get past the wall finish and insulation and condense
inside the colder wall cavity. In hot-humid climates the same thing can happen,
just in the reverse direction, humid outdoor air in the summer can condense
inside cool/air conditioned wall cavities. If enough of this happens, and the
water cannot escape, wood rot, mold, and other moisture-related problems are
likely to occur. For this reason, building codes often require installing a
vapor diffusion retarder on the warmest side of the wall cavity.
Foam board insulation is commonly
placed between the exterior finish (i.e., siding, brick) and the studs of
exterior walls. To prevent air infiltration, you should place rigid insulation
boards tightly together and seal the seams with tape or caulk. However, this
practice may worry some builders in cold climates since the foam board may act
as a second vapor diffusion retarder. Studies have shown, however, that
condensation rarely occurs in these areas unless something else is seriously
wrong with the wall assembly (i.e., massive uncontrolled air leakage into the
walls from the house.) If the assembly is constructed correctly, the inside
surface of the foam board stays warm enough to keep water vapor in its gaseous
state long enough for it to escape.
When insulating a foundation, and
although foam insulation offers no food value to insects, foam board provides
the potential for easy insect tunneling. Insect burrows reduce the R-value and
structural integrity of the insulation. For these reasons, some manufacturers
treat their foam products with an insecticide, usually a borate compound. Many
building jurisdictions also mandate treating the earth around the building with
insecticides and keeping an area bare of insulation board, several inches wide,
and all the way around the foundation of a house as an inspection area.
A better solution for below grade
walls in need of insulation is to install the foam board over the interior of
the basement walls rather than on the exterior as is more commonly done.
Interior applications prevent ground-dwelling insects from finding the foam
board at all, and it eliminates the need for the inspection area where no
insulation is allowed. However, most jurisdictions require installing a
fire-barrier over the foam board. While this adds extra cost, the thermal
performance of this method is superior in most cases to the more common foam
board application to the exterior of the foundation. This equates with a dollar
savings in energy that can repay you many times over for the additional cost
that an interior application requires. If you plan to convert a basement into a
living space there is almost no additional cost.
Foam insulation is relatively hard
to ignite but when ignited, it burns readily and emits a dense, black, smoke
containing many toxic gases. The combustion characteristics of foam insulation
products vary with the combustion temperatures, chemical formulation, and
Because of the dangers described
above, foams used for construction require a covering as a fire barrier. One
half-inch thick (1.27 cm) gypsum wallboard is one of the most common fire
barriers. Some building codes, however, do not require an additional fire
barrier for certain metal-faced laminated foam products. Check with your local
building code/fire officials, and insurers for specific information on what is
permitted in your area.