Solar TRA: Measures the heat that goes through a fabric
Optical TRA: Measures the light that goes through a fabric
TRA is an acronym method that is used to measure solar and optical performance of different fabrics.
T = Transmission: How much heat/light goes through the fabric.
R = Reflection: How much heat/light bounces off the fabric.
A = Absorption: How much heat/light is absorbed by the fabric.
Nearly all light and heat that is absorbed will enter the building, as it then radiates out into the space. If you want to look at how much heat or light will be blocked, it’s best to look at Reflection.