In order to comprehend how insulation works within your home, one needs to grasp the concepts of general heat flow and three instruments that make it happen: Conduction, Convection and Radiation.
- Conduction—Ways in which heat moves through materials. Think of pulling an item out of the oven—the heat felt through the oven mitt is an illustration of conduction. Home insulation slows conductive heat flow.
- Convection—Ways heat circulates through liquids and gases. Hot air rises, cool air sinks. Home insulation slows convective heat flow.
- Radiation—Refers to heat traveling in a straight line, heating anything solid that lies within its pathway. Home insulation reduces the acquisition of heat. It is most effective when directed toward airflow.
As a general rule, air travels from warmer to cooler until there is not a measurable difference in temperature. Thus, during the winter months hot air moves from heated areas to the colder unheated areas of your home—wherever there is a difference in temperature. Cold temperatures outside create the need for warmth inside, thus your home heating system compensates for the loss of heat. The opposite occurs during the hotter months of the year, the cold air lost is balanced out by your home cooling system. Home insulation is integral in decreasing this flow by offering resistance to the movement of heat.
All types of home insulation come with an “R-Value”, a rating applied to an insulation type’s ability to resist conductive heat flow. The higher the R-value, the more effective it is at insulating your home and is dependent upon the type of insulation, how thick it is and the density. So, the more layers of insulation stacked together and/or the more insulation in your home increases the overall R-value and thus, the overall resistance to heat flow.
A couple of factors will influence the R-value of your insulation. It comes down to how and where the insulation is placed. If compressed, or placed within the ceiling the R-value will be lesser than if the same piece was lying out in the open air, due to thermal bridging (area of an object which has a significantly higher heat transfer than the surrounding materials resulting in an overall reduction in thermal insulation of the object or building). So, when open gaps in a building are filled with insulation, they reduce convective heat loss.
A radiant barrier, looked upon as non-traditional insulation, reflects away the heat rather than absorbing it. So, a radiant barrier contains no R-value—the ability to reduce heat by reflecting it way from a space is the power of this type of home insulation.