There are many concerns which will insulate a house after it has been completed, and many of them do a very thorough job. The method usually employed is to remove a portion of the exterior wall and blow the insulation into the area between the inner and outer wall by means of air pressure.
While this is the quickest and probably the most complete way of insulating a house, the home mechanic can do an adequate job himself, provided he has the time. By taking a small portion of the house at a time, he can completely insulate during the course of the summer and save himself a great deal of money.
Types of insulation
There are several kinds of insulation. Some come in rigid sheets and can be used like wallboard. Do not, however, expect the inexpensive grades of wallboard to provide good insulation. They are not made for this purpose and should not be used for it. Another form, of insulation is the blanket type, and a third type is the dry fill.
The choice will depend upon what is to be insulated. In the case of an unfinished attic, for example, it would be impossible to use a dry fill between the roof rafters, and the choice would be either rigid or a blanket type. Likewise, in filling the space between an inner and outer wall, blanket or rigid insulation would be of little value, and dry fill would be selected.
A good insulating material, aside from being a poor conductor of heat, must be fireproof, or at least fire-resistant. Using any inflammable material between the walls of a house is a very dangerous practice.
Many materials have been tested by the Government laboratories for their insulating qualities.
The best place to start insulating a home is the attic. The greatest heat loss occurs through the roof of a house, and this can be easily verified by noting the length of time required for snow on the roof to melt. If the snow melts rapidly, an excessive amount of heat is being lost. If the snow remains for a long period, it can be assumed that the heat loss is slight. If the attic is semi finished, and is a sloped type, a very good insulation to use is the blanket variety.
Various kinds of insulating material are to be had in this form. While the initial expense of such materials as asbestos and spun glass is greater than that of cotton, wood fiber, and other cellulose compositions, the former materials offer the advantage of being fireproof while the latter are usually only fire-resistant.
Whatever the insulating material, it comes in rolls, with waterproof paper glued to one or both sides, and in standard widths. In order to be effective it must be wide enough to completely cover the space between the studs or rafters.
To install, place strips of insulation against
the sheathing and nail the edges of the paper tightly to the sides of
rafters or studs.
If asbestos or spun glass is used, the mouth and nose should be covered with a damp cloth and the hands and arms protected from coming in contact with the fibers. This is most important as the fibers are usually very irritating to the skin and to the nasal passages.
When only one side of the blanket insulation is covered by waterproof paper, be sure to place the paper on the room side and the insulating material directly against the sheathing. This will prevent most of the moisture in the air of the room from reaching and damaging the insulating material. The small amount which penetrates the paper and reaches the insulation will pass through it to the roof and do no damage.
Do not apply insulation until you are certain that the area to be covered is free from leaks.
Another way to insulate the attic roof is to use rigid insulation boards, which are made so that they can be nailed to the rafters and studding without much cutting. These boards can also be used as partitions to provide one or more rooms. To do this, put up some additional 2 x 4 studding at the point where the attic roof and floor are at least four feet apart.
Cover this studding with insulation board to form walls. Insulate the roof with sheets of the insulation nailed to the rafters. Put in any additional studding required so that the insulating board is properly supported, particularly where the board sections are joined.
Most rigid insulation boards in the home are of cellulose. These are usually made by crushing the fibers of southern pine or sugar cane and molding them into flat sheets. Gypsum boards, which are often used as wallboards or to cover a ceiling, are not true insulation, possessing no heat insulating qualities.
Cellulose boards have good insulating qualities
and are lightweight and easy to handle. They come in sizes from 4 x 4
to 4 x 12 feet.
Aluminum foil is sometimes used on insulation. It serves to reflect summer heat and keep the house cool.
An easy attic to insulate is one without finished floor and with the rafters exposed. Here, it is necessary only to insulate the attic floor. This will prevent heat from entering the attic and additional insulation on the attic roof, in most cases, will not be required. Be sure to keep the door tightly shut, as an open door provides an excellent means for warm air to escape into the attic and out through the roof.
Almost any kind of insulation can be used for this job. For dry fill insulation, put down a sheet of waterproof paper and pour the insulation over it to the desired thickness. When using blanket insulation, place it so that the paper side is on the bottom. Nail rigid insulation sheets over the roof rafters.
A great deal of heat may be lost through the exterior walls, and a brief description of their construction may help toward a clearer understanding of the insulating problem involved.
The exterior walls are composed of two separate parts, the outside and the inside wall. In between them is a dead air space cut into vertical sections by the studding. This space is about three inches wide. In a well-constructed house, this area is closed at the top and bottom to prevent circulation of air between the walls.
As a precaution against fire and to strengthen the frame of the house, horizontal pieces of two by four studding are placed between the vertical studding at each floor level. These fire-stops, as they are called, may have several bricks on top of them as added protection against fire in the basement rising through the walls.
If the inside walls are cold, go to the basement and see whether the space between the walls has been left open, allowing cold air to flow up between the walls. You can correct this condition by nailing strips of wood over the openings at the bottom and at the top, where the walls open into the attic.
Insulation between the walls helps greatly to increase the comfortableness of the house and the efficiency of the heating unit. The work is best done by a concern with the necessary blower equipment, but it can in some cases be done by the home mechanic.
To put insulation between the two walls, remove a small section of the outside wall and pour the dry fill into the space between the inner and outer wall. Measure the depth of the space before putting in the insulation, to determine whether there are any obstructions in the wall, such as fire stops, that would prevent the insulation from filling the entire space. When obstructions are encountered, mark their location on the outside wall and make an opening in the siding under the mark so that the space can be filled. Pack down the insulation from time to time while pouring.
Insulation can be added in this manner to houses whose outer walls are of wood, but it is very difficult with brick and stucco walls. Here, the best thing to do is to line the interior walls with insulating board nailed to furring strips attached to the wall. This provides a dead air space between the insulating board and the old interior wall.