Heat can be transferred in any one of three ways, radiation, convection and conduction. Radiation which is the transfer of energy through electromagnetic waves, does not require material to travel. In this way, heat can be transferred through a vacuum as the sun s heat does to warm the Earth. Convection is the transfer of heat through fluids, which include gasses like air. Conduction is the transfer of heat through material in contact with other material. Conduction operates by the energizing of molecules in close proximity to other molecules. The denser the material, the easier it is for heat to be transferred through conduction. With regard to insulation, it is the conductive mode of heat transfer that we are concerned with.
Because conduction requires the close proximity of molecules, dense materials such as solids are much better conductors of heat than sparse materials. Solids conduct much better than liquids which conduct much better than gasses. Since the molecules in gasses like air are spread far apart, they are poor conductors and hence, excellent insulators. Dense solids such as gold, silver or copper conduct much better than materials such as fiberglass. Conduction cannot occur at all where there are no atoms present to excite. Consequently, the best prevention of heat transfer through conduction is a vacuum. This is why thermoses generally have a layer where the air has been evacuated.
Thermal insulation works by creating a barrier of poorly conductive material between two environments. For example, the inside of a building and the outside are separated by an insulated wall. The best insulators use material that is not very dense and that creates pockets of air.
Materials such as glass wool, rock wool, cellulose, polystyrene, urethane foam, plant fiber, fiberglass or cork, among others, make great insulators because the material is not dense and it creates pockets of air. Polystyrene has many pockets of air trapped by a sort of plastic. Cork is a natural material that is similar.
The insulating quality of a building material is measured as quantified thermal resistance. This R value is a measure of the rate of heat transfer per unit area. R value, however does not take into account the quality of construction of the structure to be insulated, or weather factors in the local environment.
The amount of insulating material a given building will need depends on many factors. The design of the building and the location climate are important. Additionally the cost of energy relative to budget is an important consideration. These factors will need to be considered carefully in order to achieve the best possible thermal barrier for the needs of the construction project.
Local building codes will only specify the very minimum level of insulating material required. In order to create a comfortable and energy efficient environment, more insulation than the codes call for will need to be used. Often the codes are so minimal that a great deal more insulation will be needed.
Heat transfer changes over the course of the day and as the year progresses. In cold climates the basic idea is to reduce the heat flow out of the building. Windows, roofs, walls and doors are all places where a great deal of heat can be lost. In a well insulated building, windows are the biggest source of heat loss. Losses can be minimized by weatherization, bulk insulation and minimizing the number of windows and doors facing away from the sun s radiant heat.
Keep the heat inside during cold months by contacting insulation contractors today! Providing your home with the proper insulation is very essential.