Where to Install Insulation

To reduce heat loss from a house in cold weather, all walls, ceilings, roofs and floors which separate heated from unheated spaces should be insulated.

Insulation should be placed on all outside walls and in the ceiling. In houses involving unheated crawl spaces, insulation should be placed between the floor joists. If a bulk type of insulation is used, it should be well supported by slats and a galvanized mesh wire or by a rigid board.

Reflective insulation is often used for insulation of crawl spaces. Crawl spaces, as well as attic spaces, should be ventilated. A ground cover of roll roofing may also be placed on the soil of crawl spaces to decrease the moisture content of the space.

In 1 ½ story houses, insulation should be placed along all areas that are adjacent to unheated areas. These include stairways, dwarf walls, and dormers. Provisions should be made for ventilation of the unheated areas.


Where attic storage space is unheated and a stairway is included, insulation should be used around the stairway as well as in the first floor ceiling. The door leading to the attic should be weather-stripped to prevent heat loss. Walls adjoining an unheated garage or porch should also be insulated.

In flat or low-pitched houses, insulation should be used in the ceiling area with sufficient space allowed above for a clear ventilating area between the joists. Insulation should be used along the perimeter of houses built on slabs. A vapor barrier should be included under the slab.

Hot Weather

Insulation can be used effectively to improve comfort conditions within the house during hot weather. Those surfaces exposed to the direct rays of the sun may arraign temperatures of 50 degrees F or more above shade temperature and, of course, tend to transfer this heat towards the inside of the house. Insulation in roofs and walls retards this flow of heat and, consequently, less heat is transmitted through such surfaces.

Where any system of cooling hot-weather air, such as central air-conditioning, is used, insulation should be installed in all exposed ceilings and walls in the same manner as for preventing heat loss in cold weather. Or course, where cooling is used, the windows and doors would be kept closed during periods when outdoor temperatures are above inside temperatures. Windows exposed to the sun should be shaded with awnings.


Ventilation of attic and rood spaces is an important adjunct to insulation. Without ventilation, an attic space may become very hot and hold the heat for many hours. Obviously more heat will be transmitted through the ceiling when the attic temperature is 150 degrees F than if it is 120 degrees F. Ventilation methods suggested for protection against cold-weather condensation apply equally well to protection against excessive hot-weather roof temperatures.

Our Most Popular Online Tips