 Controlling
Air Leakage). You may never get another chance once the holes are hidden
under a foot or more of insulation.
Types of Insulation
Some of the common materials used for insulation
are glass fibers (fiberglass), fibers of molten rock or slag (rock wool),
recycled newspapers (cellulose), urethane foams, and even recycled cotton
fibers. Insulation comes in several forms--loose fill, batt, blanket, rigid
board, or expanding spray foam.
Loose-Fill Insulation
Loose-fill insulation consists of loose fibers or
granules, and is made from cellulose, fiberglass, rock wool, cotton, or
other materials. This loose insulation conforms to the space in which it
is installed. Loose-fill insulation comes in bags, and is usually blown
into cavities or attics with special equipment. Insulation is sometimes
blown at relatively high density into a wall or ceiling cavity to resist
air infiltration--this technique is called dense-pack.
Sometimes loose-fill fibers are cosprayed with
an adhesive or water in order to cover irregularly shaped and hard-to-reach
areas or to install in walls before drywalling. The insulation dries within
a few days and is resistant to settling. This technique is often used with
cellulose and is called wet spray. Waiting for the insulation to dry before
adding a vapor barrier to the wall can be inconvenient, so some newer processes
("moist spray") use a lot less water to speed up drying time. Some installers
also use drying machines.
Insulation can also be blown into
open wall cavities by attaching a barrier to the studs to hold it in. In
one system, a reinforced transparent vapor barrier is stapled to the studs
and cellulose is blown in through small holes, which are later patched.
A similar process involves blowing fiberglass into stud cavities behind
a net. Another system uses a temporary frame to pack cellulose, fiberglass,
or rock wool densely into the cavities. The densely packed insulation stays
in place when the frame is removed.
Batts and Blankets
Batts and blankets are flexible, bound insulation
made from glass or cotton fibers. They come in rolls or strips in standard
widths, usually to fit between framing on 16- or 24-inch centers; thickness
varies depending on the R-value desired. Blankets are available in continuous
rolls, whereas batts are precut.
Batts and blankets can fit under floors, in attics,
and in unfinished walls. Batts are easier to handle than blankets, but
blankets can be cut with a knife or razor for a perfect fit, minimizing
waste. Both are available with or without vapor retarder facings. |
An insulator at Canada's EnviroHome installs dry cellulose
insulation. The cloth mesh stapled across the studs helps contain the cellulose
during the installation process. Because of the dust generated, this man
should be wearing eye protection in addition to his dust mask.
|
Rigid Insulation
Rigid insulation is made from fibrous materials
or plastic foams and is pressed or extruded into boardlike forms. These
provide thermal and acoustic insulation, added structural strength, and
air sealing.
Plastic foam board (or rigid foam) is the most
expensive form of insulation and is made from polyurethane, polyisocyanurate,
or polystyrene. It is commonly used in exterior walls (under the siding)
and foundations. Since it provides a high R-value per inch of thickness,
it is useful where a lot of insulation is desired in cramped quarters,
such as cathedral or vaulted ceilings. Foam insulation must be covered
with finishing material for fire safety.
Rigid insulation is being used in innovative
ways in new construction. Stressed skin walls can replace traditional framing
with panels consisting of a foam core with structural sheathing glued to
both sides. They usually use expanded polystyrene (EPS) or polyurethane
foam, and are impermeable to moisture on both sides. Some new stressed
skin wall systems actually use compressed wheat straw sandwiched between
oriented strandboard (OSB). These also have high R-values, and have been
used in other countries for years.
The fiberglass batt is one of the most well-known
insulation types. Here, installers have carefully cut batts to fit around
pipes and electrical outlets, insuring complete insulation coverage.
|
Another new construction technique
uses all-in-one exterior insulation and finish systems (EIFS) that have
a finish similar to stucco and can be cut in various shapes. Unfortunately,
many homeowners have had wall decay and termite problems when moisture
became trapped under the EIFS. Meticulous installation is critical to avoid
such problems.
Some builders now use rigid foam form blocks--generally
made from expanded polystyrene--stacked so that their hollow centers are
aligned. The cavities are then filled with concrete, and sometimes reinforcing
bars, to create an insulated structural concrete wall.
Foam in Place
Foam-in-place materials require special equipment
to meter, mix, and spray or extrude into place. They provide air sealing
as well as insulation. Polyurethane and polyisocyanurate foams have high
insulation values per inch. Another type of foam, called Icynene, is also
becoming more popular in energy-efficient new construction. These foams
can be sprayed into open wall cavities, where they expand to fill the space.
Excess material is then trimmed off and, in some cases, used in the attic
as loose fill. Spray foams are particularly helpful for insulating difficult
areas like sill plates. |
Radiant Barriers
Radiant barriers are made of aluminum foil with
backing. Rather than slowing heat conduction as insulation does, they stop
heat from "radiating" through the attic. Radiant barriers can reduce attic
temperatures in hot climates, so that the difference in temperature between
the house and attic is not so great. Based on the same concept, a radiation
control (reflective) coating on the roof can lower the summer roof temperature
in hot places. Since they reduce radiant rather than conducted heat, it
is difficult (and inappropriate) to associate R-values with radiant barriers
or radiation control roof coatings.
Figuring Out What You Need
How much insulation your house should have depends
on your climate, energy costs, budget, and personal preference. You may
be able to get guidance on insulation levels appropriate for your area
from your utility's energy conservation department, the local or state
building code, an independent energy auditor, or an insulation contractor.
Remember that the building code gives the minimum legal level of insulation
for new homes. Put in more if you have high energy bills or want to be
more comfortable.
The U.S. Department
of Energy (DOE) has a list of recommended levels of insulation in ceilings,
walls, floors, and foundations, broken down by zip code. In general, you
should put at least R-30 in your attic even in milder climates, and up
to R-49 in the coldest parts of the United States. Floor insulation may
not be necessary at all in the warmer states, but in most parts of the
country R-19 is recommended. Wall insulation is recommended in all climates,
but the amount can be limited by the space in the wall cavity. Using fiberglass
or cellulose in a 2 x 4 wall will usually give you from R-11 to R-13. However,
you can get R-19 in a 2 x 6 wall cavity, and even more if you use rigid
insulation beneath the siding. Call the
Energy
Efficiency and Renewable Energy Clearinghouse for DOE's specific recommendations
for your zip code.
| It is almost always easier and more
effective to install more insulation during initial construction than to
add it later. If you're building a new home, make sure all the areas in
Figure
1 are insulated to code or beyond. Some areas are impossible to go
back and insulate after the house has been built--for example, the sill
plate (the joint between the top of the foundation and the bottom of the
house frame).
Still, you can add insulation to most places
in existing homes. Attics are typically the easiest to get to, but insulation
can be blown into empty wall cavities, attached under floors, and added
to basement or crawlspace walls. On the other hand, retrofit foundation
insulation may be prohibitively expensive, and adding more insulation to
partially insulated walls is usually difficult and impractical. |
Rigid foam insulation can be used in exterior walls
(under the siding), foundation, and other places where space is limited.
The high R-value per inch of thickness is especially useful where a lot
of insulation needs to fit into a small amount of space.
|
How Much Do You Have Already?
To decide how much insulation to add to your home,
you need to know how much is already there. If you don't have an energy
auditor inspect your home, you should look for insulation in several places.
Check all the recommended insulation areas in
Figure
1. In each location, measure the thickness of the insulation and identify
which type of insulation was used (see Table 2).
First, check the attic; take a few measurements with a ruler in different
areas (away from the access hatch, where insulation is more likely to have
been disturbed or compacted) and average them.
In unheated garages and basements and above crawlspaces,
the structural framing (the joists of the floor above, or the wall framing
studs) is often exposed, making it easy to examine the insulation. You
may find batts, blankets, or rigid insulation there. An unvented crawlspace
may also have insulation on the perimeter wall.
]If your house is relatively new, it may have
insulation outside the basement or foundation wall. However, this insulation
will not be visible, because it will be covered by a protective layer of
plastic, fiberglass, metal flashing, or rigid protection board. The builder
or the original homeowner may be able to tell you if such exterior insulation
was used.
Next, inspect exterior walls. One method is to
remove the cover plate from an electrical outlet or switch on the inside
of the wall, and shine a flashlight around the sides of the box. Often
you can catch a glimpse of insulation in the gaps around the outlet box.
A plastic crochet hook (don't use metal unless you first turn off the power
to the outlet) is useful for pulling out a bit of the material for identification.
Check outlets on a few different walls on each floor, and make a separate
check in any parts of the house that were built at a different time. Rigid
insulation is difficult to identify in finished walls. One way to look
for it is to remove and then replace a small section of the exterior siding
and sheathing.
Selecting a Type
The type of insulation you use will depend partly
on the spaces that you plan to insulate. For example, since you cannot
conveniently blow insulation into an open overhead space, batts, blankets,
or spray products are used between the joists of an unfinished basement
ceiling. The only way to fill closed cavities in finished walls (without
tearing them open) is with blown-in insulation.
Table
1 provides a summary of the appropriate applications for the various
types of insulation. See "Comparing Insulation Materials" for other considerations
in choosing which type to use.
Installing Insulation
After planning the R-values and type of insulation
that will be put into your home, make careful installation a priority.
Batts are particularly susceptible to poor installation--it is easy to
leave gaps that drastically reduce their effectiveness. Blown-in loose
fill insulation can also be improperly installed. Some installers "fluff"
the insulation (adding more air than they should), so that it takes up
more space, but has a lower insulation value. Certain brands of loose-fill
insulation come with an "Inches = R-value" guarantee; they are guaranteed
by their manufacturer to achieve a given level of R-value when installed
to a designated thickness.
Ceilings
Adding insulation to an unheated attic is usually
straightforward. If there is no attic flooring, either loose-fill insulation
can be blown in or fiberglass batts can be laid between the joists. If
existing insulation comes up to the top of the joists, an additional layer
of unfaced batts can be added perpendicular to the joists. This helps to
cover gaps in the first layer. Insulation should be even and should cover
corners. Also insulate and weatherstrip the access door or hatch. If access
to the attic is limited, blown-in insulation will work best.
To ensure proper air circulation, make sure the
insulation does not block vents. For roof vents, 12 inches of clearance
is usually recommended. For eave vents, little clearance is necessary,
as long as the vents are not obstructed. Keep insulation away from recessed
light fixtures, and other fixtures that emit heat, to avoid fire hazards.
Some newer recessed lights are IC (insulation cover) rated and can safely
be buried by insulation.
Unless the attic already has some insulation,
add a vapor retarder when you insulate. Most batts and blankets have a
kraft paper vapor retarder on one side. This prevents excessive moisture
from condensing in the insulation, which could reduce its effectiveness.
The vapor retarder must be installed on the warm side of the insulation
(face down in cold climates, face up in hot climates), or it can do more
harm than good. When additional insulation is placed over existing insulation,
do not install a vapor retarder, as it may trap moisture in the insulation
underneath.
Do not store anything on top of ceiling insulation.
When insulation is packed down, it tends to lose effectiveness.
Insulating a sloped cathedral ceiling can be
much more difficult. There is little room between the ceiling and roof,
and the cavity is difficult to access. The best method is to add rigid
foam on the outside when reroofing. Another method is to drill holes in
the drywall from the inside and blow insulation into the joist cavities.
However, moisture can accumulate in the insulation if there is no ventilation
in the cavity. Some people go so far as to build an attic and put on a
new roof, so that there's more room for insulation.
Walls
Finished wall cavities are best insulated by an
experienced contractor. The installer must drill holes in the sidewall
and blow the insulation into each cavity between the studs.
For new construction, there are more options.
Batts, wet-spray cellulose, or loose fill blown in through a barrier can
be installed between the studs, and rigid board insulation can be put up
before the siding is installed. Re-siding also presents a good opportunity
to put rigid board insulation between the old siding and the new.
When installing batt insulation, don't compress
it to fit behind electrical boxes--this will create areas around the boxes
where the insulation is not fully expanded. Cut the insulation around any
obstructions. Follow manufacturer's recommendations on stapling the facing
to the studs.
Some people do use compressed batts for the whole
wall, though. For instance, you can install a 6-inch R-19 fiberglass batt
into a 3 1/2 inch stud cavity (which would normally take an R-13 batt).
The compression will reduce the R-value to about R-17. This technique is
especially useful in older homes, where 2 x 4 studs are truly 4 inches
deep (modern 2 x 4s are only 3 1/2 inches deep).
Basements
If the basement space is unheated, it may be best
to insulate between floor joists (basement ceiling) instead of around the
foundation (basement floor and walls). Unfaced fiberglass batt insulation,
supported from below with metal supports or wire mesh, can do the job.
If you insulate above an unheated basement, also insulate any ducts or
pipes running through this space (especially in cold climates where pipes
might freeze), since the space will become colder in winter.
Polyurethane foam insulation is sprayed into open
wall cavities.
|
If you choose to convert an unheated
basement into insulated living space, the simplest method is to build 2
x 4 frames against the concrete foundation walls, insulate with batts or
blankets, and cover with drywall. Another method is to attach wood furring
strips to the walls by nailing or bonding. The insulation can then be stapled
or tacked into place. Drainage problems may need to be addressed to ensure
that no exterior water leaks into the basement, and the concrete should
be treated with water seal or vapor barrier paint.
Benefits of insulating the basement walls and
floor can include decreased condensation (which can help prevent mold and
mildew), reduced energy losses from ducts running through the basement,
and reduced risk of pipes freezing in winter. |
Slab Floors
Insulating a slab foundation requires digging around
the foundation at least 6 inches down. Attach rigid foam board; add a protective
covering, such as fiberglass panels, treated plywood, or cement coating;
then fill in and compact the soil. Although the slab will be insulated
only at the edges, this is where most of the heat loss occurs.
Crawlspaces
If a crawlspace is ventilated, insulate the floor
above it. Batts are generally installed between the floor joists and must
be well supported so they don't sag or fall down. The batts should touch
the floor boards continuously and should not be compressed. This is easier
said than done. Insulating can be difficult while lying on your back, and
getting the batts to stay up against the floor is a challenge. Common methods
include using wire mesh (chicken wire) fastened to the joists under the
batts, metal supports held up by tension between the joists, or wood lath
supports attached perpendicular to the joists 18 inches apart. The best
method is to use batts that are the exact thickness of the floor joists
and support them with wire mesh. When you insulate the floor above a crawlspace,
insulate all ducts and water lines running through the space, especially
in cold climates where they might freeze.
Insulate crawlspace walls only if the crawlspace
is dry all year, the floor above is not insulated, all ventilation to the
crawlspace is blocked, and a vapor barrier (for example, 4- or 6-mil polyethylene
film) is installed on the ground to reduce moisture migration into the
crawlspace. Insulation batts can be fastened to the sill plate and draped
down the wall. Because the insulation will be exposed, be sure to use either
an unfaced product or one with the appropriate flame-spread rating. If
you live in a very cold region, you should continue the insulation over
the ground (on top of the moisture barrier) for about 2 feet from the wall.
Figure 1. Where to insulate in a home.
I In unfinished attic spaces, insulate between the floor joists.
2 In finished attic rooms with or without dormer, insulate:
2A between the studs of "knee" walls
2B between the studs and the rafters
2C between the studs of "knee" walls
2D extend insulation into joist space to reduce air flows
3 Insulate all exterior walls, including:
3A walls between living spaces and unheated garages or storage areas
3B foundation walls above ground area
3C foundation walls in heated basements
4 Insulate floors above cold spaces, such as vented crawl spaces
and unheated garages, and:
4A any portion of the floor in a room that is catilevered beyond
the exterior wall below
4B slab floors built directly on the ground
4C foundation walls of crawl spaces and perimeter plates
4D Extend insulation into joist space to reduce air flows
5 Caulk and seal around all windows and doors
If You Do It Yourself
Whether to install insulation yourself depends on
several factors. Placing batts in the attic floor is usually relatively
easy (if the attic is roomy), requiring only laying the material between
the parallel ceiling joists. A homeowner can often insulate basement or
crawlspace walls, or floors over unheated areas, using rigid, batt, or
blanket insulation. Installing loose-fill insulation with blowing equipment
is a job best left to the professional installer, and sprayed-on insulation
also requires a qualified contractor. Adding insulation to a mobile home
is complex and should generally be done by specialists, as well.
If you do decide to do it yourself, follow the
manufacturer's instructions, and take these precautions:
-
Wear clothing adequate to protect against skin contact
and irritation. A long-sleeved shirt with collar and cuffs buttoned, long
pants, gloves, hat, safety glasses, and dust respirator are advisable in
all do-it-yourself insulation projects.
-
Do not cover or pack insulation around bare stovepipes,
electrical fixtures, motors, or any heat-producing equipment, such as recessed
lighting fixtures unless they are IC rated--insulation can trap heat and
prevent air from circulating. Install baffles to prevent insulation from
getting within 3 inches of these fixtures.
-
Do not cover attic vents with insulation. Proper
ventilation in attics helps prevent overheating in summer and moisture
buildup all year long.
Table 2. Identifying Old
Insulation
Material Description R-Value per inch(1)
Fiberglass batts Pink, yellow, or white, 3.2
blanket-like
Loose-fill fiberglass Pink, yellow, or white 2.2
loose fibrous material
Loose-fill rockwool Denser than fiberglass, 2.9
"wooly", usually grey
with black specks
(some newer products
are usually white
Loose-fill cellulose Shredded newspaper, 3.5
gray, "dusty"
Vermiculite Gray or brown granules 2.2
Perlite White or yellow granules 2.7
Misc. wood products Sawdust, redwood bark, 1
balsa wood
Urea formaldehyde foam(2) Whitish grey or yellow, 4
very brittle foam
Asbestos(3) May be mixed with other 1
materials--difficult
to identify
_____________________________________________________________________________
1. These R-values are for old insulation only. They take into account settling, as
well as average R-values for old materials that may have changed with new products.
2. Urea formaldehyde foam is no longer sold due to concerns about formaldehyde
off-gassing
3. If you suspect you have asbestos, consult a hazardous material specialist before
disturbing the insulation
If You Have It Done Professionally
Obtain cost estimates from several contractors for
a stated R-value. But remember that you want good quality materials and
labor, not just a good price. Ask them to describe the procedure they will
use, as well as the insulation type and R-value.
Ask the contractor to attach vertical rulers to the joists prior to
an attic loose-fill installation. This can help you to see if the proper
depth was installed. Also, the installer should provide a signed and dated
statement describing the type of insulation; the thickness, coverage area,
and R-value; and the number of bags used or pounds installed.
| You may want to have your attic R-value
evaluated to ensure that you are getting what you paid for. "Cookie-cutting"
(measuring and weighing a sample section of insulation) is the insulation
industry recognized procedure of evaluating installed loose-fill insulation.
Many independent companies offer cookie-cutting services to homeowners
throughout the country. Contact the Insulation Contractors Association
of America for a list of companies that offer these services.
Many companies offer home energy audits, in which
professionals evaluate the energy efficiency of the home, identify the
amount of insulation needed, and indicate where retrofits will be most
economical. Energy utilities may also offer this service, as well as loans
or other incentives to insulate. Another useful resource is the state energy
office. Some states offer technical advice, tax credits for money spent
on home insulation, and financing for retrofits. |
This installer puts extruded polystyrene rigid board
insulation in place. Like rigid foam, this board insulation fits in tight
spaces. It can be installed in walls during new construction or when residing
an existing wall.
|
Resources
Loose-Fill Insulations, DOE/GO-10095-060,
FS 140, Energy Efficiency and Renewable Energy Clearinghouse (EREC), May
1995.
Insulation Fact Sheet, U.S. Department of Energy, update to be
published 1996. Also available from EREC. Call EREC with your insulation
and other energy questions. Tel:(800)363-3732.
Lowe, Allen. "Insulation Update," The Southface Journal, 1995,
No. 3. Southface Energy Institute, Atlanta, GA.
ICAA Directory of Professional Insulation Contractors, 1996,
and A Plan to Stop Fluffing and Cheating of Loose-Fill Insulation in
Attics, Insulation Contractors Association of America, 1321 Duke St.,
#303, Alexandria, VA 22314, (703)739-0356.
Jeanne Byrne is managing editor of
Home
Energy.
Sidebar
Controlling Air Leakage
Most people are aware that air leaks into their
houses through small openings around doors and window frames and through
fireplaces and chimneys. Air also enters the living space from other unheated
parts of the house, such as attics, basements, or crawlspaces. It leaks
in through gaps around electrical outlets and switch boxes, recessed fixtures,
pull-down stairs, furred or false ceilings, and plumbing connections.
The attic--not the front door--is the best place
to start air sealing. Hot air rises, and you're likely to find bigger holes
between your house and attic than around doors and windows. Look for and
seal the tops of wall cavities that open into the attic, especially over
interior walls for the kitchen and the bathroom. Gaps may also be found
where the attic level changes. In the basement, look at the joint where
the basement ceiling meets the foundation wall. Seal all these holes before
insulating, using gypsum board (such as Sheetrock) or any permanent rigid
barrier, such as sheet metal, plywood, foam board, or cardboard. (Anything
exposed should be fire resistant.) Cut the barrier to fit and seal it with
caulk. Also weatherstrip the edges around the attic trapdoor or entry door.
There are often large holes around pipes (look
under your sinks and behind your toilets) and ducts penetrating the walls
or the attic floor. If the pipes or ducts are metal, you can fill the area
around them with urethane foam. If the pipes are plastic, foam won't work
well because the pipes will change size depending on their temperature.
You can put insulation into a plastic garbage bag and stuff this tightly
into the gap.
Other areas to seal before insulating the attic
are chimney or furnace flue penetrations. Most fire codes allow sheet metal
to bridge the gap between the chimney and the attic floor, and the joint
between the sheet metal and the chimney can be sealed with furnace cement.
Some insulation methods actually air seal as
well, and are useful for areas that are difficult to get to. For instance,
dense-pack cellulose is very effective at reducing air leakage and is often
used for walls and restricted ceiling cavities. Rigid board insulation
and urethane foams also provide air sealing along with high R-values as
insulation.
Next, seal cracks around windows and doors where
you notice drafts and leaks. Windows and doors should be weatherstripped,
and gaps between the framing and rough opening should be filled with caulk
or foam sealant.
You may want to call a professional air sealing
specialist, energy services company, or insulation contractor to seal your
house. They should use air leakage detection and measuring tools, such
as blower doors and infrared cameras, to help them find the biggest leaks.
Sidebar
Comparing Insulation Materials
There are often several types of insulation that will suit a particular
job. While they all serve the same purpose, there are some differences.
R-Value
The greater the R-value, the greater the insulating power. However, it
is total R-value that is important. An insulation's R-value per inch is
most significant when only a few inches are available--as in walls or cathedral
ceilings, or in attics with very low roof slopes. Rigid foam boards have
the highest R-value per inch. Fiberglass batts have higher R-values per
inch than loose-fill fiberglass. Of the loose-fill insulations, cellulose
and rock wool have somewhat higher R-values per inch than fiberglass.
Rigid foam and sprayed-in foams pack the most insulating capability
into the thinnest area. Another advantage to using rigid insulation under
wall siding is that the insulation covers the studs. In contrast, since
loose-fill or batt insulation fills in between the studs, a significant
part of the wall--the studs themselves--remains at only about R-3.
Settling
Cellulose tends to settle by about 20% over the first few years after installation,
losing about 20% of its R-value. Therefore, manufacturers are required
to state the "settled" thickness needed to achieve a given R-value. Initially,
you need to install 20%-25% more than the settled thickness. Fiberglass
and rock wool settle too, but not nearly as much.
Settling of wall insulation is particularly troublesome, because it
can leave a void at the top of the wall cavity that is completely uninsulated.
Settling can be avoided by blowing insulation at higher than usual density
(3 1/2 lb/cubic foot for cellulose, and 1 1/2 lb/cubic foot for fiberglass).
This technique is referred to as dense-pack and also helps prevent air
leakage.
Weight and Density
Cellulose and rock wool are generally denser, and therefore heavier, than
fiberglass. When high R-values (R-38 or more) are installed, their weight
could cause some drywall ceilings to sag, but only if the ceiling is 1/2
inch drywall with framing spaced 24 inches on center--a rare combination.
For most ceilings, the drywall is 5/8 inch thick or the framing is 16 inches
on center, and there should be no problem with any of the insulation types.
Insulation that is installed at low density tends to lose R-value in
extremely cold weather, due to natural air circulation through the insulation.
This affects fiberglass loose-fill insulation blown in at typical densities
of 1/2-1 lb/cubic foot, sometimes cutting its insulation capability in
half. It may also occur with some new "low-density" cellulose loose-fills.
If you live in a climate that has extremely harsh winters, use denser loose-filll
products (rock wool or standard or dense-pack cellulose), blankets, or
sprayed-in foam, which do not suffer from this problem.
Fire Resistance
All loose fill insulation must meet
Consumer
Product Safety Commission standards for fire safety. Fiberglass and
rock wool are naturally fire resistant, and cellulose is treated with fire-retardant
chemicals. The kraft paper or standard foil facing on some batt insulation
is flammable and should not be exposed once installed. It's generally fine
in attics or crawlspaces where it's installed against the ceiling or floor.
Some batt facings are rated as flame resistant, and unfaced batt insulation
is flammable and should not be exposed once installed. It's generally fine
in attics or crawlspaces where it's installed against the ceiling or floor.
Some batt facings are rated as flame resistant, and unfaced batts are available.
Use rigid foam insulation in an exposed area only if it has a flame-spread
index at or below 25 (the label should say FS25).
Health Considerations
Recently questions have arisen as to whether airborne glass fibers cause
lung cancer. The fire-retardant chemicals, dust, and newspaper ink in cellulose
also may cause irritation or health problems. If you're installing insulation
yourself, avoid any such risks by using a good respiratory filter mask,
as well as safety glasses, gloves, and any other protection recommended
by the manufacturer.
If you've ever handled fiberglass before, you know that skin contact
can make you itch. A new type of fiberglass batt called Miraflex has curly
fibers designed to be less itchy and to create less dust. Other options
for the do-it-yourself installer include fiberglass batts wrapped in perforated
polyethylene plastic or thin fabric, which prevent the fibers from getting
onto your skin and clothing.
Environmental Concerns
Several types of insulation use recycled materials. Fiberglass is made
from molten glass, usually with about 20%-30% recycled content (mostly
industrial waste glass, but some manufacturers use postconsumer bottles).
Cellulose is made from waste newspaper and sometimes boxes, shredded into
small, fibrous particles, which are mixed with fire-retardant chemicals.
Rock wool is made from industrial by-products, mainly iron ore blast furnace
slag. A new cotton insulation is made from mill waste cotton and polyester.
Urethane, styrene, and isocyanurate foams are made from petrochemicals.
Some polystyrene insulation uses as much as 50% recycled resin, half of
which is postconsumer plastic. Polyisocyanurate foam usually has at least
9% recycled plastic (some of it PET beverage containers).
The production of foam insulations creates some
toxic pollution. Most foam insulations no longer use chlorofluorocarbons
(CFCs) as blowing agents because they deplete the ozone layer. However,
some still use hydrochlorofluorocarbons (HCFCs), which are less potent
ozone depleters. There are several products available that use neither
CFCs nor HCFCs, such as Icynene, which uses a mixture of carbon dioxide
and water.
It takes energy to save energy, at least when it comes to insulation
manufacturing. Cellulose requires much less energy to produce than any
other type of insulation. However, any of the insulation types should still
save far more energy in your home than was used to produce it.
Publication of this article was made
possible through funding from the U.S. Environmental Protection Agency
and the U.S. Department of Energy's Office of Building Technologies.
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