Figure 5-27.—Types of insulation.
wool, wood fibers, shredded redwood bark cork wood
pulp products, vermiculite, sawdust, and shavings.
Fill insulation is suited for use between first-floor
ceiling joists in unheated attics. It is also used in
sidewalls of existing houses that were not insulated
during construction. Where no vapor barrier was
installed during construction, suitable paint coatings, as
described later in this chapter, should be used for vapor
barriers when blow insulation is added to an existing
house.
Reflective
Most materials have the property of reflecting
radiant heat, and some materials have this property to a
very high degree. Materials high in reflective properties
include aluminum foil, copper, and paper products
coated with a reflective oxide. Such materials can be
used in enclosed stud spaces, attics, and similar
locations to retard heat transfer by radiation. Reflective
insulation is effective only where the reflective surface
faces an air space at least 3/4 inch deep. Where this
surface contacts another material, the reflective
properties are lost and the material has little or no
insulating value. Proper installation is the key to
obtaining the best results from the reflective insulation.
Reflective insulation is equally effective whether the
reflective surface faces the warm or cold side.
Reflective insulation used in conjunction with
foil-backed gypsum drywall makes an excellent vapor
barrier. The type of reflective insulation shown in figure
5-27, view D, includes a reflective surface. When
properly installed, it provides an airspace between other
surfaces.
Rigid
Rigid insulation (fig. 5-27, view E) is usually a
fiberboard material manufactured in sheet form. It is
made from processed wood, sugar cane, or other
vegetable products. Structural insulating boards, in
densities ranging from 15 to 31 pounds per cubic foot,
are fabricated as building boards, roof decking,
sheathing, and wallboard. Although these boards have
moderately good insulating properties, their primary
purpose is structural.
Roof insulation is nonstructural and serves mainly
to provide thermal resistance to heat flow in roofs. It is
called slab or block insulation and is manufactured in
rigid units 1/2 inch to 3 inches thick and usually 2- by
4-foot sizes.
In building construction, perhaps the most common
forms of rigid insulation are sheathing and decorative
covering in sheet or in tile squares. Sheathing board is
made in thicknesses of 1/2 and 25/32 inch. It is coated
or impregnated with an asphalt compound to provide
water resistance. Sheets are made in 2- by 8-foot sizes
for horizontal application and 4- by 8-foot (or longer)
sizes for vertical application.
Miscellaneous
Some insulations are not easily classified, such a
insulation blankets made up of multiple layers of
corrugated paper. Other types, such as lightweight
vermiculite and perlite aggregates, are sometimes used
in plaster as a means of reducing heat transmission.
Other materials in this category are foamed-in-place
insulations, including sprayed and plastic foam types.
Sprayed insulation is usually inorganic fibrous material
blown against a clean surface that has been primed with
an adhesive coating. It is often left exposed for
acoustical as well as insulating properties.
Expanded polystyrene and urethane plastic forms
can be molded or foamed in place. Urethane insulation
can also be applied by spraying. Polystyrene and
urethane in board form can be obtained in thicknesses
from 1/2 to 2 inches.
5-21
