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New Types of
Insulation
Insulation consists of a variety of materials
and comes in many forms. These include fibrous insulation, foam insulation,
insulated panels, straw panels, and insulating masonry products, as well as
specialized devices to aid proper insulation techniques. Alternatives to
conventional fiberglass, cellulose, and mineral wool are constantly being
explored and introduced to the market place. These new types of insulation serve
different needs. The following describes the new insulation types without
manufacturer or product name unless it is needed to convey an adequate
description. In order to convert English (Imperial) unit R-values into metric
(International System units, or SI) equivalents, you can use the conversion
factors listed before the bibliography.
Fibrous Insulations
Fiberglass Insulation
Manufacturers now produce medium and
high density fiberglass batt insulation with higher R-values (ft2h°F/Btu)
than existing low density batts. These new products are appropriate for
insulating building envelopes with limited cavity space (for example,
cathedral ceilings). Medium density batts have twice the fiberglass as the low
density batts, and the high density batts have three times as much. Because
they contain more fiberglass, these higher density batts are more expensive
than low density batts.
High density fiberglass batts for
insulating 2 ´ 4 inch (38 ´ 89 millimeter[mm]) stud-framed wall construction
are rated at R-15, compared to R-11 for standard batts and R-13 for medium
density batts. A medium density batt for 2 ´ 6 inch (38 ´ 140 mm) frame wall
construction is rated at R-21. For cathedral ceilings, high density batts
rated at R-30 for 8 1/2 inch (216 mm) spaces, and R-38 for 10 inch (254 mm)
spaces are available.
One manufacturer markets an
unconventional fibrous insulation product. It is a combination of two types of
glass strands laminated together. This new form has several advantages over
conventional fiberglass. The natural, random curl of the material greatly
reduces skin irritation, produces high loft, and requires no chemical binder.
The combined glass strands are larger than the fibers implicated in
respiratory diseases.
At approximately R-3 per inch, it
compares well to a conventional fiberglass batt. It is currently available
only in a perforated plastic batt configuration. Similar insulations, without
the plastic wrapping, "accordion," or stretch out, when you attempt
to lift them.
Cotton Insulation
Cotton thermal insulation is available
as batt or loose fill. It consists of recycled cotton, polyester, and nylon
fibers, and is treated with a flame retardant and insect/rodent repellents. It
meets the same Class I standards for fire resistance as fiberglass insulation.
The batts come in standard widths, thickness', and R-values with a Kraft paper
facing on one side. Unlike conventional fiberglass insulation, cotton
insulation does not irritate the skin when being installed. Cotton insulation
is not yet readily available in all sections of the country. Check with your
local building supply store or the manufacturer for ordering information (see
the manufacturer contact list below).
Mineral Wool Insulation
Mineral wool refers to three types of
insulation made from raw materials spun into loose fill or batt products:
- "glass wool," or
"fiberglass," made from recycled glass or silicates;
- "rock wool," made from
virgin basalt, an igneous rock; and
- "slag wool," made from
steel-mill slag.
Most of the "mineral wool" made
in the United States is actually "slag wool". Most U.S.-made mineral
wool is stiff and brittle. Mineral wool insulation is fire resistant and aids
sound-proofing.
A softer, mineral wool batt product is
now available. The edge of this new Canadian-made batt is highly compressible.
This allows insertion of the batt between framing members. It then expands to
continuously press against both framing members. The result is a friction-fit
installation that increases the overall insulation effectiveness. This batting
is more dense than fiberglass, so it should be less subject to air convection
thermal losses. Its thermal resistance is approximately R-3.7 per inch.
Until recently, the friction fit batt
was only available outside the United States. The cost of soft mineral wool
batt insulation is about 15% higher than fiberglass, and it is still more
fragile than fiberglass.
Plastic Fiber Insulation
Another new type of insulation entering
the marketplace is plastic fiber insulation. Plastic fiber batts are made from
recycled polyethylene terephthalate (PET), commonly used to make milk
containers. The fibers are thick, making extremely soft batt insulation that
looks like high-density fiberglass. R-values vary with batt density:
- R-3.8 per inch at 1.0 lb./ft3 density
- R-4.3 per inch at 3.0 lb/ft3 density
The recycled content and clean
manufacturing process help make this insulation a good addition to the market.
The insulation also does not irritate the skin. It does not burn when exposed
to an open flame, but it melts at a low temperature-a definite disadvantage.
The batts are also difficult to cut with standard job-site tools, and the
insulation tends to accordion when handled. Major U.S. insulation
manufacturers are expected to produce plastic fiber insulation products within
the next few years.
Other Fibers
Several other fibers are being analyzed
for their potential insulating properties. The most notable of these include
wool, hemp, and straw. Wool and hemp insulations are commercially available in
the United States. Both products offer similar R-values to other fibrous
insulations. Straw is a form of cellulose with reasonably good insulating
properties.
Straw bale construction opportunities,
once popular with pioneers, are gaining favor with cost-conscious, hands-on
homeowners interested in energy efficiency. Depending on the orientation of
the straw, bales tested according to ASTM procedures resulted in bale R-values
of R-2.4 to R-3.0 per inch. One straw bale expert claims R-2.4 is more
representative of in-situ straw bale construction. A typical medium-sized,
three-wire bale may be 23 x 16 x 42 inches (610 x 406 x 1067 mm), weigh 75-85
pounds (34-38.5 kilograms (kg)), and yield R-56.5 walls (or R-2.4/inch). The
smaller 18 x 14 x 36 inch (457 x 356 x 914 mm) bales, at 50-60 pounds
(22.7-27.2 kg), can create R-43.2 (or R-2.4/inch) assemblies. Compressed straw
board products are beginning to enter the construction market as well.
Insulating Foams
Urethane Foam
A new closed-cell polyurethane foam
insulation uses HFC-134a, a nonchlorine blowing agent, which is not
athmospheric ozone-depleting. The new product offers a reported aged R-value
of R-6.5 per inch thickness. Because of the new blowing agent, it is roughly
three times as expensive as traditional polyurethane insulations. Although it
does not affect the ozone layer, a recent study showed that high
concentrations of HFC-134a in the environment may damage wetlands and plant
growth.
Low density open-cell polyurethane
foams-0.5 pounds per cubic foot (lb/ft3) versus 2.0 lb/ft3(8.0-32.0 kilograms
per cubic meter (kg/m3)) for conventional urethane-are similar to conventional
polyurethane foam. These "half-pound urethanes" are semi-flexible,
cellular plastics. While most polyurethane insulations use ozone-depleting
fluorocarbon blowing agents, low density varieties use water or carbon dioxide
(CO2).
Half-pound urethanes may be sprayed in
place where exposed cavities are common, such as in new construction. One
manufacturer offers a slightly different formulation, which trained installers
pour into cavities. This is unique for an expanding foam, since most foam
insulation applications of this sort cause bowed and disconnected interior
sheathing. The foam is water vapor permeable, while remaining flexible, water
repellent, and resistant to wicking of moisture. Polyicynene provides good air
sealing and yields R-3.6 per inch thermal resistance.
Half-pound urethane's current installed
cost is approximately $1.05 to $1.30 per square foot ($11.25-14.00 per square
meter [m2]) to fill a 2 ´ 4 inch (38 ´ 89 mm) stud cavity, compared to $1.75
per square foot ($18.83 per m2) for conventional polyurethane. As with most
plastic foams, protect it from exterior exposure and sheathe the interior with
an approved fire barrier. This foam insulation will not sustain a flame upon
removal of the flame source.
Nitrogen-based Plastic Foam
One manufacturer, Tailored Chemical
Products, Inc., markets a two-component plastic foam insulation system that
uses compressed air as the installation medium. It is commonly used for
filling commercial and industrial masonry walls. Although this nitrogen-based
(urea formaldehyde) plastic resin takes only a minute to set, complete curing
may take several weeks. Unlike polyurethane insulations, this product does not
expand as it cures. The product also breathes better than polyurethane,
allowing moisture vapor to pass through it.
The manufacturer does not recommended
this product for attic or ceiling applications for two reasons: it seeps
through small cracks, and the product breaks down at prolonged temperatures
above 190°F (88°C). It contains neither petrochemicals nor fire retardant
chemicals. This insulation has an R-value of about 4.6 per inch and costs are
competitive with loose-fill or poured-in insulations.
Cementitious Insulation
Air-Krete™ is a magnesium silicate,
cementitious (cement-based) insulation that is foamed or pumped into closed
cavities. Do this before installing the inner wall finish material. Installed
consistency of the foam is similar to shaving cream that then cures to
something akin to thick pudding. It is easily damaged by water. (See article
titled "Air Krete-The Other 'New' Kid on the Block" in Bibliography
below.)
This insulation is made from material
extracted from seawater. Its non-toxic attributes make it very popular with
chemically sensitive individuals. Since it is not temperature sensitive, it
can be installed indoors under any weather conditions. This insulation is also
non-flammable. Air-Krete™ has an R-value of about 3.9 per inch and costs
about $1.50 per square foot ($16.15 m2) to fill a 2 ´ 4 inch (38 ´ 89 mm)
stud wall cavity.
Phenolic Foam
For several years, a high R-value
phenolic rigid insulation board was on the market. Because the foam boards
often shrank, warped, or decomposed, manufacturers stopped making it.
Foamed-in phenolic insulation is still available. It has a R-4.8 per inch
resistance value, uses air instead of an ozone-harming fluorocarbon as a
blowing agent, and has good fire resistance. The manufacturer does not
restrict installation due to extreme temperatures, providing it is not left
permanently exposed. The major disadvantage of phenolic foam is its shrinkage,
which ranges from 0.5 to 1.5%.
Foam Insulation Vehicles
At least one company has created a foam
"vehicle" that transports one or more insulating materials such as
fiberglass into a cavity. This foam later dissipates, leaving the encapsulated
insulation uniformly distributed in the cavity. The product's R-value matches
the internally applied insulating material.
One brand of insulation uses high
quality fibers such as fiberglass, mineral wool, or cellulose. The thermal
resistance value generally approaches the upper limit of attainable R-value of
these materials. Its binder is a latex formulation, similar to household glue,
and may not be suitable for some individuals. This form of insulation is
commonly used in manufactured housing outside of the United States.
Another brand employs a latex adhesive
binder to homogeneously install standard loose-fill insulation materials. The
product uses a proprietary blown-in technique and is not foamed-in. Refer to
the R-values for the three types of insulation:
- Fiberglass: R-4.0 to R-4.3 per inch
- Mineral Wool: R-3.8 per inch
- Cellulose: R-3.7 per inch
Rigid Insulating Panels
Composite Insulating Panels
Composite insulation panels include
structural insulating panels (SIP) and insulated roof panels. Structural
insulated panels, "insulated sandwich panels," or "stress(ed)-skin
panels," consist of an insulated core sheathed on two sides. The
insulation is usually a foam-based plastic such as polystyrene or isocyanurate,
but foam-straw composites are occasionally available. Sheathing materials
include plywood, oriented strand board (OSB), and waferboard; interior
sheathing materials also include drywall. The panels range in size, but are
most common in 4 ´ 8 and 4 ´ 9 foot (1.2 ´ 2.4 and 1.2 ´ 2.7 meter)
varieties.
Because of its integral strength,
composite panel systems reduce the need for structural lumber, opportunities
for air leaks, and job site assembly time. A comparison of stick-built and
panel-built test houses shows a slight energy saving with structural panel
construction. Because these panels also reduce sound transmission, some
professionals use them for interior partitions.
Insulated roof panels have a nailable
sheathing layer over an insulation base, typically rigid foam. Use this
product only where you need sheathing on one side, for example; a retrofit
application over an existing sheathed roof. These panels are very effective at
increasing the R-value of a roof. Scandinavians have used this type of
application for years to help prevent condensation inside attics. The
insulated roof panels are also available with air channels just under the
exterior sheathing for ventilated roof designs.
Straw Panels
Compressed-straw panels have been used
in hundreds of thousands of buildings worldwide. The process of fusing straw
into boards under pressure requires no adhesive. It was developed in the
1930s. Panels are usually 2 to 4 inches (51-102 mm) thick and faced with
heavy-weight Kraft paper on each side. Although manufacturer claims vary,
R-values realistically range from about R-1.4 to R-2 per inch. These
sound-absorbing panels also make effective interior partitions. Some
manufacturers have developed structural insulated panels from
multiple-layered, compressed-straw panels.
Insulating Masonry Products
Manufacturers have also developed a variety
of innovative permanent insulated concrete form systems. These systems include
internally braced, rigid foam board formwork and stackable hollow-core foam
blocks. The rigid board formwork consists of exterior panels of rigid
polystyrene or polyurethane separated by structural plastic ties. Adding
appropriate reinforcing and poured concrete follows. Since the insulated
formwork remains in place, the result is an insulated concrete wall assembly.
Because of its flammability, building
codes do not permit exposed interior foam insulation in habitable spaces. With
insulated concrete form systems, you must sheathe the interior foam surface
with an appropriate fire-resistant material. Most codes accept fire-resistant
drywall as an acceptable fire retarder. Also, do not overlook the need to
protect the exterior insulation from damaging solar radiation (ultraviolet
light degrades the plastics) and physical impact (dents, scratches, and
abrasions).
Other systems use the rigid insulation
board in the center of the concrete wall. These systems are particularly
applicable to insulated tilt-wall construction, where walls are poured within
bordering forms laid on a concrete slab, then raised, or "tilted,"
into position. Because the insulation board is inside the wall, it reduces
potential problems relating to building security, fire, and insect
infestation.
Stackable, permanent insulation block
systems typically involve use of hollow core, rigid polystyrene or
polyurethane blocks that interlock to create the formwork for the walls.
Concrete around steel reinforcing inside block cavities structurally
stabilizes the wall assembly. While one manufacturer's concrete-coated,
expanded polystyrene 12 inch (305 mm) thick block wall with concrete infill
yields a very fire-resistant R-24 assembly, this is unique to the stackable
insulation block systems.
Insulation blocks and formwork
connecting inner and outer insulation faces with bonding struts of rigid foam
provide insects direct access through this wall element. Since many insects
burrow within these insulations, a better solution may be to pick a system
that uses an insect resistant material.
Today, lightweight, insulated concrete
blocks take on many different shapes and compositions. The better concrete
masonry units reduce the area of connecting webs as much as possible. The
cores are filled insulation-poured-in, blown-in, or foamed-in-except for those
cells that require structural steel reinforcing and concrete infill. This
raises the average wall R-value.
Some block makers coat polystyrene beads
with a thin film of concrete. The concrete serves to bond the polystyrene
while providing limited structural integrity. Expanded polystyrene mixed with
Portland cement, sand, and chemical additives are the most common group of
ingredients. These make surface bonded wall assemblies with a wall R-value of
R-1 per inch thickness. Polystyrene inserts placed in the block cores increase
the unit thermal resistance to about R-2 per inch.
Hollow-core masonry units made with a
mix of concrete and wood chips are also available. You install them by
stacking the units without using mortar (dry-stacking). Structural stability
comes from the concrete fill and appropriate reinforcing required throughout
for structural walls. The wood component is subject to the effects of moisture
and insects, however.
Two varieties of solid, precast
autoclaved concrete masonry units are now available in the United States:
autoclaved aerated concrete (AAC), and autoclaved cellular concrete (ACC).
This class of material has been commonly used in European construction since
the late 1940s. Air makes up 80% (by volume) of the material. It has ten times
the insulating value of conventional concrete. The R-1.1 per inch blocks are
large, light, and flat with a consistency much like a hard, fine sponge. When
laid with a thin mortar layer, plaster and stucco provide simple, attractive
finish treatments. Autoclaved concrete is easily sawn, nailed, and shaped with
ordinary tools. Since the material absorbs water readily, it requires
protection from moisture.
Precast autoclaved cellular concrete
uses fly ash instead of high-silica sand as its distinguishing component. Fly
ash is a waste ash produced from burning coal in electric power plants. The
fly ash is the material that differentiates ACC from AAC.
Specialized Devices
A wide variety of rigid insulation inserts
are available to fill many critical locations in the insulated envelope of
houses. Some examples are to use inserts as air chutes, insulation dams,
concrete block fillers, and ice dam retarders. Expanding foams efficiently
seal and weatherize homes. Devices as simple as cardboard can be used to
provide an insulation dam to help keep loose-fill insulating material around
attic ductwork.
Conclusion
Many types of alternative insulation are
rapidly becoming incorporated into conventional construction. They may provide
a more convenient and often healthier approach to increasing the energy
efficiency of a building. It is important to note, however, that because these
new materials have been on the market for a short time, they may not be widely
available. Therefore, performance for some of these materials may be poorly
documented. Always research a material's characteristics and suitability to a
particular situation before buying any of these new products.
Conversion
FACTORS
| R-Value Conversions |
To Get |
Multiply |
By |
| Thermal Resistance (R) |
RSI (m2 C/W) |
R(ft2h F/Btu) |
0.1761 |
| Insulation R/unit Thickness |
RSI/mm |
R/in. |
0.00693 |
Note: The standard unit of measurement
in the United States has been the Imperial unit. The country is converting to
the international System (SI) unit, or metric standard, which predominates
internationally. To differentiate like terms, you may find 'SI' added to the
term symbol. For example, RSI refers to the R-value in International System (SI)
units (metric).
Bibliography
The following articles have information about
new types of insulation. This bibliography was reviewed in August 1997.
"Air-Krete-The Other 'New' Kid on the Block," J. Nisson, Energy
Design Update, (6:12) p. 10, December 1987.
"Alternatives in Low-Density
Foam," Journal of Light Construction, (15:1) pp.11, 14, October
1996.
"Brick Veneer for Non-Masons," Journal
of Light Construction, (11:9) p. 43, June 1993.
"Bug-Free Foam Panels," Journal
of Light Construction, (13:5) p. 49, February 1995.
"Cavity Fill Insulation:
Alternatives," A. Wilson, New England Builder, (6:12) pp. 73-74,
September 1988.
"Cotton Insulation-Move Over
Fiberglass?" J. Nisson, Energy Design Update, (11:9) pp. 9-11,
November 1991.
"Cellulose Batts Again," J.
Nisson, Energy Design Update, (15:5) p. 15, May 1995.
"Demo Highlights Cost and Efficiency
of Panel Houses," S. Culpepper, Fine Homebuilding, (No. 95) p. 38,
May 1995.
"Ener-Grid (Rastra)-Not-So-Miraculous
R-Value," Energy Design Update, (16:10) pp. 8-9, October 1996.
"Fast Foundations," C. Silver, Practical
Homeowner, (1:7) pp. 90-92, September 1991.
"Fiberglass Insulation: Is
High-Density Fiberglass Really Cheaper in the Long Run?" B. Greenlaw, Fine
Homebuilding, (No. 93) p. 108, February/March 1995.
"Foundation Forms That
Insulate," M. Reier, Fine Homebuilding, (No. 76) pp. 36-41, August
1992.
"Foam Finds Use as Lightweight
Backfill," Journal of Light Construction, (12:10) p. 12, July 1994.
"Foam-Core Panel Versus Stud-Frame
Construction-Side-by-Side Test Results," J. Nisson, Energy Design Update,
(13:7) pp. 4-5, July 1983.
"Fly-Ash Concrete: Turning Waste into
Walls," Journal of Light Construction, (12:3) p. 6, December 1993.
"Foam Foundation Forms," S.
Andrews, Journal of Light Construction, (12:3) pp. 31-34, December 1993.
"Foam Home Kits," J. Nisson, Energy
Design Update, (15:6) pp. 10-11, June 1995.
"High-R Insulation Baffles and Air
Chutes," J. Nisson, Energy Design Update, (13:2) pp. 9-10, February
1993.
"Innovative Building Products," Journal
of Light Construction, (12:10) pp. 32-37, July 1994.
"Insulating Concrete Formwork,"
J. Nisson, Energy Design Update, (13:2) pp. 10-14, February 1993.
"Insulation Materials: Environmental
Comparisons," A. Wilson, Proceedings of the Twelfth Annual International
Energy Efficient Building Conference and Exposition, Energy Efficient
Building Association (EEBA), Inc., Dallas, TX, February 23-26, 1994, pp.
A169-79, $15.00 (nonmember paper reprint), $ 35.00 (members), $ 45.00
(nonmembers). Proceedings available from EEBA, 1829 Portland Avenue,
Minneapolis, MN 55404-1898, (612) 851-9940. The paper is also available in the
following publication: Environmental Building News, (4:1) pp. 1, 11-17,
January/February 1995.
"Insulation Update: Super Batts and
Cotton Batts," Journal of Light Construction, (10:4) p. 10, January
1992.
"Miraculous(?) Concrete Building
System," J. Nisson, Energy Design Update, (15:4) pp. 7-8, April
1995.
"Most Versatile Foam-Form Building
System," J. Nisson, Energy Design Update, (15:3) pp. 10-13, March
1995.
"New Stay-in-Place Insulating
Concrete Form System," J. Nisson, Energy Design Update, (15:2) pp.
7-8, February 1995.
"New Study Measures the Energy
Savings of ICF Walls," Energy Design Update, (17:5) p. 9, June 1997.
"New from Canada: Icynene
Insulation," R. Harrington, Journal of Light Construction, (10:9)
pp. 31-33, June 1992.
"New Lightweight Spray Foam-Move Over
Icynene(?)" J. Nisson, Energy Design Update, (16:7) pp. 9-11, July
1996.
"Plastic Fiber Batts-the 'Next'
Insulation Material?" J. Nisson, Energy Design Update, (13:9) pp.
12-13, September 1993.
"Product Spotlight: Insulation,"
Custom Builder, (10:4) pp. 76-80, 82-84, 86, 88-89, May/June 1995.
"The Revolution Behind Your
Walls," C. Wardell, Popular Science, (246:4) p. 43, April 1995.
"Revolutionary Soft Fluffy Fiberglass
from Owens-Corning," J. Nisson, Energy Design Update, (14:10) pp.
9-10, October 1994.
"Rockwool Batts," J. Nisson, Energy
Design Update, (13:6) pp. 12-15, June 1993.
"Self-Ventilating Foam Roof
Panels," J. Nisson, Energy Design Update, (15:6) pp. 13-14, June
1995.
"Soft Mold Batt Installation
Foam," J. Nisson, Energy Design Update, (15:11) pp. 10-11, November
1995.
"Spray Urethane Foam with Zero Ozone
Depletion Potential," J. Nisson, Energy Design Update, (13:5) p. 12,
May 1993.
"Straw: The Next Great Building
Material?" A. Wilson, Environmental Building News, (4:3) pp. 1,
11-17, May/June 1995.
"The Three Classes of Fiberglass
Batts," J. Nisson, Energy Design Update, (10:3) p. 11, March 1991.
"The 'Ultimate' Duct
Insulation," J. Nisson, Energy Design Update, (14:2) p. 14, February
1994.
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