The Importance of Insulation in Your Home

Insulation Perth provides resistance to heat flow, lowering heating and cooling costs. It is especially important to include insulation at the time of new construction and in any home remodel.

Insulating materials typically have dead air spaces or cells to slow the transfer of energy. Fiberglass, cellulose, mineral rock wool and foamed plastics are common insulation materials.

Thermal Conductivity is one of the primary insulating properties of materials. It determines how easily heat can move through a material, and is usually measured in W/(m.K). Materials with high thermal conductivity tend to be used as heat sinks, while those with low thermal conductivity are used as insulators.

A material’s thermal conductivity is determined by the speed at which its molecules vibrate and interact with each other. This determines how easily or slowly the heat moves through a material, and the distance that it travels. The higher the thermal conductivity, the faster it will transfer heat.

Insulating materials use various mechanisms to block or slow the flow of heat through them. Some of these materials, such as air and gases, are effective at insulating because they have a large number of gas-filled pockets that obstruct heat conduction pathways. Others, such as expanded polystyrene (commonly referred to as Styrofoam) and silica aerogel, function by trapping air in a structure, which blocks the movement of thermal energy.

The thermal conductivity of insulation is influenced by a number of factors, including its temperature and moisture content. This is because heat is transferred through the material by molecular vibration, and the rate at which this occurs will vary depending on the temperature.

Because of the effect that temperature has on the thermal conductivity of insulation, it is important to be able to accurately calculate its value under different conditions. This is because calculations based on thermal conductivity are not accurate when comparing it to other measurements made under different conditions.

The R-values and U-values of insulation are largely dependent on its thermal conductivity. However, the R- and U-values take into account other insulating properties, such as thickness, which is not accounted for in the thermal conductivity. This means that the U- and R-values are more useful in describing how well a particular insulation performs, than its thermal conductivity alone. This is especially important, since it gives engineers a more complete picture of a material’s performance in the context of a thermal insulation system. It also helps ensure that the correct product is selected for a particular application.


The basic function of insulation is to slow the transfer of heat into and out of a building. This is achieved by reducing thermal conduction, convection and radiation. A good insulator minimizes all three forms of transfer to increase the efficiency of a heating system and reduce energy costs.

The most common form of transferring heat is conduction. This happens when a cold surface touches a hot object, such as a person touching the handle of a metal skillet. Insulation prevents this type of heat transfer by providing a barrier between the cold and hot surfaces. The material used to insulate is also designed with low thermal conductivity and a high specific heat capacity to decrease the rate of transfer.

Electrical conduction occurs when charged particles in one material pass through another material and lose their charge. This is the process that makes it possible to use electricity through a wire. Insulation prevents this by using materials that are not electrical conductors and by creating air pockets between the conducting objects.

Convection is the movement of heat energy in a liquid or gas by its vibrations. For example, water moves from a warmer place to a cooler place when you put it in the refrigerator. Insulation can prevent convection by reducing the temperature gradient and by blocking the motion of the liquid or gas.

Radiation is the transfer of heat energy by electromagnetic waves. You can feel radiant heat from a fire when you sit near the campfire, even though you are not in direct contact with it. Insulation can prevent this by reflecting radiant heat, or by absorbing it and holding onto it.

The ability of a material to resist the transmission of heat through it is called its thermal resistance, usually expressed as R Value. The higher the R value, the more efficient the insulator. R values are typically determined by a formula involving a material’s thermal conductivity and its thickness, and can vary greatly between different materials. The R value of a specific material is also affected by changes in moisture and dimensional instability.


The heat energy in your home moves through three different ways – conduction, convection and radiation. Insulation is a material that blocks these forms of energy transfer and slows the flow of heat into and out of your building.

Conduction is the transfer of heat through direct contact between materials. Metals are great conductors of heat, whereas concrete and masonry are better insulators. Insulation is a material with low thermal conductivity, and the thicker it is the greater its insulating properties.

Heat also transfers through convection, which occurs when fluids (either air or water) move from areas of higher to lower temperatures. This can happen naturally or as a result of forced convection. The way in which a material resists the movement of fluids is often reflected in its U-value and R-value.

Unlike conduction, convection can be reduced by limiting the amount of solid material within an insulation product. In order to slow the movement of air, insulation is designed with small voids or air pockets in which heat is trapped. This is a good reason why it’s important to air seal a construction before adding insulation. Moisture makes it easier for convection to take place and reduces an insulation’s effectiveness.

Radiation is the transfer of heat by electromagnetic waves. This is the way in which you feel warmth radiating from a fire, or sunlight coming through a window. This form of heat transfer can be minimized by using reflective surfaces in the construction of a building.

The best insulation is made with a combination of materials that block all three types of heat transfer. This is why it’s important to get advice before deciding on what type of insulation you need. Ideally, your insulation will be rated with a U-value and R-value that exceeds the requirements of your climate zone and cladding system. It is also important to ensure that your insulation is properly installed and fitted with no gaps or voids, and that it is a consistent thickness. The quality of your insulation will also affect its performance and R-value.


Radiation is the transfer of heat energy through electromagnetic waves (electromagnetism). Insulation can reduce the flow of radiation from hot surfaces to cooler surfaces. Insulation can be effective in minimizing convection and radiation, but to maximize its effectiveness it must be installed properly and air-tight. Insulation can also be used to reduce the flow of electricity from conducting wires.

Bulk insulation uses pockets of trapped air within its structure to resist the flow of conducted and convected heat. Its ability to resist radiant flow depends on its bulk density and its surface emissivity, which is proportional to the square root of its thermal conductivity. Bulk insulation materials include fiberglass, rockwool, cellulose, natural and recycled fibers. Rigid foam board insulations and radiant barriers use polyurethane or other gases in their cells to resist conductive heat flow, but also have low surface emissivities.

Reflective insulation mainly resists radiant heat flow by reflecting its rays. It is usually shiny aluminum foil laminated to paper or plastic and can be purchased as sheets (sarking), concertina-type batts or multi-cell batts. The insulative properties of reflective insulation depend on keeping an air space of at least 25mm next to the shiny surface. Contact with any other material or the occurrence of dust on the surface quickly diminishes its performance. It is therefore best to keep the reflective surface facing downwards (except in Climate zone 1).

It is impossible to calculate the radiative conductivity of fibrous insulation materials from bulk density, surface area or porosity because of the need to resolve the complex radiation transfer equation. This requires Monte Carlo ray tracing or experimental measurement to obtain the absorbing phase function and scattering phase functions for individual fibrous particles. However, a good approximation can be obtained by assuming that the absorption and scattering phases are equal for a given porosity, and by assuming that the emissivity of the binding material is negligible. These calculations give results which compare favorably with experimental rates of heat transfer in evacuated insulations.