Thermal Performance refers to how well a structure responds to changes in external temperature during the daily and seasonal cycles.
The coefficient of heat transmission or thermal transmittance, a U-Value is a measure of heat loss/transfer of heat through a structural element (which can be a single material or a composite). It is calculated on the rate at which heat transfers through 1 square metre of a structure, where the temperature difference between the inner and outer face is 1 degree Celsius.
U-value measures the rate of heat transfer. This means that products with a lower U-value will be more energy efficient. R-value is a product’s resistance to heat flow which means that the higher the product’s R-value, the better it is at insulating a home and improving energy efficiency.