The purpose of installing insulation is to reduce heat loss and is part of the thermal barrier of a home.
Remember: The thermal barrier protects the envelope from heat loss/heat gain. Basically, it is the blanket that keeps a house warm.
The purpose of the thermal barrier is to keep the heat in the home longer during winter, and keep the heat out longer in the summer.
A main source of heat loss within the building envelope is through conduction; all walls, floors and ceilings which separate a heated area from an unheated area require a thermal barrier ( e.g. Insulation) to be installed. Insulation allows a home to retain heat in the winter and remain cool in the summer. The greater the amount of insulation, the less heat transfer occurs. The minimum amount of insulation that is required within a building is determined by the climate and the local codes for a given location.
Thermal control criteria:
Refer to SB-12 and the appropriate building codes as it requires one of the three following values to be met for insulation levels:
Improperly installed Insulation can cause major heat loss issues for a building. This can greatly increase the cost of heating the home and may also cause occupant discomfort. Failure of this layer is caused by water ingress which significantly reduces the ability to control heat flow.