Although insulation can be made from a variety of materials, it usually comes in four types - batts (blankets), rolls, loose-fill, and rigid foam boards. Each type is made to fit in a different part of the house. Batts are made to fit between the studs in walls or between the joists of ceilings or floors. Batts are usually made of fiber glass or rock wool. Fiber glass is manufactured from sand and recycled glass, and rock wool is made from basaltic rock and recycled material from steel mill wastes. Rolls or blankets are also usually made of fiber glass and can be laid over the floor in the attic. Loose-fill insulation, usually made of fiber glass, rock wool or cellulose, is blown into the attic or walls. Cellulose is usually made from recycled newsprint treated with fire-retardant chemicals.
Rigid foam boards are made of polyisocyanurate, extruded polystyrene (XPS), expanded polystyrene (EPS or beadboard), or other materials. These boards are lightweight and may provide a small amount of structural support. Rigid board insulation is made to be used in confined spaces such as exterior walls, basements, foundation and stem walls, concrete slabs, and cathedral ceilings.
Fiberglass Insulation3 1/2" = R-11
6" = R-19
Loose fill for attics is R-3 per inch
Used in walls, floors over crawl spaces, attics, crawl space stem walls
How it's Made and Available Products
Fiberglass insulation resembles cotton candy, and the manufacturing process even resembles a large cotton candy machine. However, instead of sugar, the main ingredient is silica sand. The sand is heated to a high temperature where it melts and flows as liquid glass. The glass is then spun into fibers through a very fine extrusion process. It is collected and sprayed with binders (glue) and shaped into large blankets of various thicknesses. It is then cut into strips for rolled product or left large for batt products. If it will have a paper backing, it is added last. Kraft paper is sprayed with a hot tar-like substance that acts as the vapor barrier and causes the fiberglass to stick to the paper.
Loose-fill fiberglass is made
in the same process, but the last step is a chopper.
Old style 'rock wool' insulation is made in a similar process, but the raw material was coal boiler and blast furnace slag. It is darker in color (usually gray), is much heavier, and contains a lot of impurities that appear as black specs and particles that did not form into spun fiber.
When fiberglass is made, it is nearly white. Colors are added for name-branding purposes.
Fiberglass can also be pressed into high-density boards and used as sheeting (like plywood) and fabricated into other products such as rigid fiberglass ductwork common in commercial buildings.
Advantages
relatively inexpensive
very light-weight
drys out if it gets wet and retains R-value
good R-value per inch thickness
Disadvantages
can be a skin irritant when handling
does not block the wind
can be blown around if attics are improperly vented (too windy)
does not provide an integral vapor barrier
Methods of Installation and Use
rolled out between studs and joists during new construction
blown into attics as loose fill
blown into walls as a retrofit
sprayed into open walls with a binder (glue) during new construction
nailed on as sheeting using rigid board products
rolled out as batts/blankets in attics and under floor joists
Other Notes
R-value does NOT increase if compressed; ie: placing an R-19 or 6" thick roll in a 3 1/2" stud cavity does NOT give R-19; it gives R-11. The value of the insulation is in the trapped air space, not the fiberglass material. If density is increased to the point that air is squeezed out and more glass is present, then R-value can actually go DOWN per inch.
For best results, fiberglass should be installed with a vapor barrier on the warm side, and a wind block (house wrap or sealed sheathing) on the cold side
Cellulose InsulationR-2 to 3 per inch
Blown in attics
Blown into wall cavities as a retrofit
Sprayed with a binder (glue) into open wall cavities of new construction
How it's Made and Available Products
Cellulose, which takes it name from wood fiber, is made from recycled newspaper, phone books and other light paper products. Depending on the quality of the manufacturing process, the product can vary from still being able to read bits of words, to a homogenous fluffy gray powder. The ground paper is treated with fire retardants and various other agents to improve its resistance to water and make it easier to handle.
Advantages
the least expensive to purchase
easy to handle and install
a good fire block (an insulated attic does not easily burn)
a fair wind block (denser)
Disadvantages
lower R-value per inch than most other insulation products in use today
losses it R-value when wet and does not recover well if saturated wet
tends to settle in attics and when blown into walls without binders (glue), losing R-value
does not provide an integral vapor barrier
Methods of Installation and Use
attics and closed wall cavities
Other Notes
Cellulose can be highly fluffed by a good blowing machine during installation, which if measured in depth, can give a false R-value. Final (settled) R-value can be determined according to the number of bags used and the square foot covered (according to information generally available on the bags), or by measuring the depth a couple years after installation.
Rigid Foam BoardsR-3 to R-9 per inch
not all are water resistant
most are not sunlight resistant
used as insulating sheathing
flammable
How it's Made and Available Products
Rigid foam board is made in two different processes, Expanded and Extruded. Expanded is the process used to make 'bead board'.
'Bead Board' is made of expanded polystyrene beads (packing peanuts) pressed and cut in board shapes. Its strength and R-value varies with density. If you look at it closely, or break it, its bead structure shows. Bead board should NOT be used underground, or anyplace where it can get wet, as moisture will cause it to fall apart. Bead board has the lowest R-value, the lowest first cost, and the lowest strength of all foam boards. It is maybe R-3 per inch.
Extruded Polystyrene is styrene foam board made in an extrusion process. It has a closed-cell structure which makes it water-proof and stronger. It is the most common product used underground to insulate basement walls and floor slabs. It has an average R-value of R-5 per inch. Extruded polystyrene has some structural benefits.
Extruded Polyisocyanurate is urethane foam board extruded with an inert gas filling its pours. It is generally foil-faced to seal in the gas and protect the foam surface. Urethane foam is much softer, can take on water if damaged (punctured) and should not be used underground. It has the highest R-value of all foam boards at about R-9, depending on its density and gas used. The foil also provides a reflective surface, which some have tried to claim as a higher R-value. The reflective value has limited application.
Advantages
the highest R-values per inch
easy to handle and install
a good wind and water block
Extruded Polystyrene and Polyisocyanurate with a foil face are vapor barriers
Disadvantages
highest first cost
flammable
mainly used as rigid sheets (old spray-in foams no longer used)
Methods of Installation and Use
nail, glue, or otherwise attach as rigid board products
Other Notes
never use expanded foam underground
all foam boards must be covered with a fire barrier when used in interior residential construction
For more information see Foam Sheathing
Reflective Barrierslayer or layers of aluminum foil against a dead air space
better at stopping solar gain in hot climates than stopping heat loss in cold climates
How it's Made and Available Products
Reflective foil "insulations" became very popular and CONTROVERSIAL in the mid-1980's. Using the 'thermos bottle' as the example, reflective barrier manufacturers made outrageous claims about their effective R-value. Independent testing eventually dismissed the outrageous claims, but certain products did have value in certain applications and are still available. Reflectivity does have an advantage when it is facing a dead air space (good thermos bottles use a near-vacuum) or in very high temperatures - such as an attic in a southern climate. The surface must also stay clean (shiny) to be effective.
Very thin layers of aluminum foil are laminated or otherwise manufactured together with other materials, such as paper or poly (bubble wrap) to improve handling and application.
Advantages
good solar gain barrier in attics in southern climates
Disadvantages
expensive
difficult to install correctly
little to no value for heat-loss, which is mostly conductive and convective
For more information see Reflective Insulation
Vermiculite and Perlitepour-in insulation
seldom used in new residential construction
about R-2 per inch
How it's Made and Available Products
Vermiculite and Perlite are aggregate-based products that are most commonly used in commercial and industrial construction for filling the open cavities of concrete blocks.
Another popular use for both products is planting soil conditioners and fillers. Vermiculite is the gray-silver looking stuff that looks like chunks of sawdust, and the perlite is the white crunchy stuff that resembles light-weight ceramic chips.
Both products have been used in residential attic and wall insulation.
Advantages
inexpensive
easy to handle
good fire-barriers
impervious to moisture
Disadvantages
low R-value
heavy (as compared to other insulation products)
Other Notes
There is some controversy over the health risks of vermiculite insulation. For comparative views on the issues see:
EPA Report at www.epa.gov/asbestos
A vermiculite manufacturer's view point at www.schundler.com
Links to Manufacturers Web Sites Referenced on this page
Fiberglass = Owens Corning = www.owenscorning.com
Cellulose = Cellulose Insulation Manufacturers Association www.cellulose.org
Reflective Insulation = distributor at = www.betterinsulation.com/foilform.htm
Vermiculite and Perlite = www.schundler.com and EPA at www.epa.gov/asbestos
For information about Urea-Formaldehyde Insulation see UF Foam Insulation
For more information about fiberglass insulation, go to the North American Insulation Manufacturers Association (NAIMA) web site at www.naima.org
Source: Text Bob Fegan 8/2003; images from Owens Corning web site at www.owenscorning.com 8/2003; reflective attic barrier image from www.betterinsulation.com/foilform.htm 8/2003; cellulose info from www.cellulose.org 8/2003; vermiculate info from Schundler Manf at www.schundler.com and EPA at www.epa.gov/asbestos/insulation.html; vermiculate images from EPA web site 8/2003;