OPAQUE is a software tool for calculating properties of wall or roof surfaces like U-value, Time Lag, and Decrement Factor. 

It models single or multiple layer compositions, aiding in Heat Gain/Loss calculations. Users create custom composite surfaces from a material library, view them in 2D or 3D, and analyse variables such as Outdoor/Sol-Air Temperatures and Heat Transfer. 

OPAQUE uniquely includes microencapsulated Phase Change Material (PCM), estimating daily Energy Reduction efficiently when PCM is used.