The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California

First Aid For The Ailing Houses

INSULATING MATERIALS

With one exception (see section on Metal-foil Insulation) the insulating effect of a material is the result of air confined in small spaces, as, for instance, in wood fibers, in cork, in spongy materials, and between fibers that are matted. A solid wood board has a good degree of insulation, for heat passes only slowly through the air cells in the fibers. In certain of manufactured insulating materials, wood is ground into fibers, and the fibers are matted together into sheets. Because of the air confined between the matted fibers as well as within them, a sheet of this material has a greater insulating effect than the original solid wood of the same thickness. A sheet of wood-fiber insulating board 1/2 inch thick will have about the same insulating effect as a solid board 11/2 inch thick.

For these materials, insulating value depends on thickness. Thicknesses of material in stiff-sheet form much below 1/2 inch will have too little effect in be worthwhile. For most purposes, 1 inch will give good results; 2 inches will not give double the effect, but only half as much more. For materials in looser form, not having sufficient strength to support themselves, a greater thickness is advisable.

Because of their thinness, building paper and building felt have no value as insulation but are useful when added to insulation to prevent vapor passage. Also because of its thinness, there is no insulation in any variety of paint.

Insulating materials are of three general types: stiff and rigid sheets having considerable strength, flexible blankets with or without coverings of heavy paper, and loose fibers or granular powder.

While insulating material is most effective when used for no other purpose than insulation, the stiff sheets are often applied as sheathing boards or in place of lath, for the sur- , face is sufficiently open for plaster to penetrate and cling. When covered with plaster, the insulating effect will be reduced by as much as one-third, for the plaster in penetrating will displace air from between the fibers.

Stiff sheets are usually 4 feet wide and 8 or more feet long. They are sawed, nailed, and handled as lumber. For information on their application, see section on Wallboards.

Flexible or blanket insulation is usually nailed or stapled between studs or beams, and in the center of the space, to form a layer of dead air on one or both sides. The insulating effect will be greater than if the material is placed against a surface.

Rock wool can be had loose, to be placed in handfuls, or matted into pads of a width to fit between rafters, beams, and studs, and 3 feet or so long. When placed between floor beams, these pads remain in position by their own weight; when placed between rafters, they can be held by cross wires.