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1947-48 Theatre Catalog, 6th Edition, Page 180 (168)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 180
Page 180

1947-48 Theatre Catalog, 6th Edition, Page 180

Thermal Insulation with Mineral Wool

Operational Efficiency and Patron Comfort

Increased through Fire-Proof Insulations

Architects and heating engineers are generally agreed today that the theatre, church, public hall-in fact, any human - occupied building e which does not have thermal insulation is out of (late, uncomfortable, and inefficient.

So important is insulation regarded that government agencies, mortgage lenders, fire-prevention experts, and other groups have been urging such protection for many years. Building owners who have applied insulating material in existing structures have found that it results in substantial savings in fuel costs, air-conditioning costs, and generally adds to the comfort of occupants both winter and summer.


The purpose of thermal insulation is to retard as much as possible the passage of heat to the outside in winter and to the inside during the hot suinmer months. Walls and roofs are not designed as heat barriers. Their principal function is to keep out rain, snow, wind and the direct rays of the sun. For that reason, some means must be provided to retard the fiow of heat.

Almost any material will offer some resistance to the passage of heat, but those which have the highest resistance *in other words, the lowest conductivity *are naturally the most efficient. Known by architects and engineers as the ffkfactor," the conductivity of various materials has been measured scientifically. Those having the smallest k-factor are regarded as the best insulators.

The following table of k-factors of commonly used substances is cited by the United States Bureau of Mines in its latest treatise on insulation (Information Circular, No. 7388, October, 1946):

Mineral Wool .27 to .30 Cotton .29 Wood pulp board with

plaster base .30 to .40

PRODUCTION OF MINERAL WOOL starts with cm ordinary pile of limestone or glass. A workman shovels the material into a special cupola or furnace (below). After melting, a jet of high velocity steam hits liquid mass (right) converting it into the widely familiar wooly material.

rock and mineral slag


.lrchiturlural Engineer

Flax fiber .. .31 to .83

Sugar cane r.. .34

For example, engineers have found that 4 inches of an insulating material placed between the auditorium ceiling and roof will lower interior temperatures as much as 15 degrees on hottest days. And in winter the occupied space is more uniformly and comfortably heated with at least a third less fuel.

Numerous theatres and other places of public assembly which have insulation and are air conditioned have reported savings in operating their aircooling equipment during one season sufficient to pay for the entire insulation job.

It is, however, the saving in fuel costs, combined with increased efficiency of heating plants and occupant comfort, that causes theatre and other public building owners to insulate their structures. Long periods of intense firing of the furnace are not necessary in an insulated structure, according to the Construction Research Bureau, of New York, clearing house for building information. And it removes the cold, clammy feeling so often found in churches, halls and auditoriums which are not used every day and when furnaces are banked a large part of the time.


There are four principal types of insulation on the market: Flexible, filltype, reflective, and boards.

The fill-type is most generally used in existing buildings, because it can be blown through a hose into the walls and ceiling without upsetting normal routine or creating any dirt or muss.

The fiexible type is manufactured in batts, quilts, or blankets, backed with

vapor-resistant paper. This finds its greatest use in new construction, being nailed in place between studs or furring strips and joists as the structure goes up. It also is nailed in place in existing buildings Where the space to be insulated will accommodate a workman.

Boards must be applied during construction or within accessible spaces, and this is true also of refiective insulation.

Numerous materials are processed in various ways and used as thermal insulation. Among them are wood fiber, sugar cane fiber, cotton, various metals, and mineral wool, which is made from rock, slag, sand, and other materials.

A few manufacturers have recently placed on the market paints which are claimed to have insulating value. These and metal sheets insulate by reflecting heat back toward its source.

The mineral wool and vegetable fiber products derive their insulating properties from countless dead air cells within the fibers and these are the types most commonly used.

Reflective insulation has not received very wide acceptance.

All of the fibrous insulating materials are fabricated into the fiexible type. Materials include cotton, balsam wool, other wood and vegetable fiber products, and mineral wool. Of these, only the latter is widely manufactured in loose or granular form to be blown into walls and ceilings of existing structures. It is obvious that the blanket or Hexible type cannot be installed within a finished wall. Blowing is the only means of reaching inaccessible spaces.


No insulation will make a building fire-proof, but some of the materials now in use are highly fire-resistant. Because it is a mineral product, mineral wool cannot burn. National Bureau of Standards tests show that a wood-lath

1947-48 Theatre Catalog, 6th Edition, Page 180