A U-value, Time Lag, and Decrement Factor calculator opaque wall or roof surfaces.

OPAQUE calculates the U-value, Time Lag, and Decrement Factor for wall or roof opaque surfaces composed of a single or multiple layers. These can be used to calculate the Heat Gain or Loss through the surface. Composite surfaces are constructed by the user from a library of materials and displayed in two or three dimensions. In addition, 2-D plots of Outdoor and Sol-Air Temperatures, Radiation variables, and Heat Gain/Loss through the envelope can be displayed. A unique new feature of OPAQUE allows the inclusion of microencapsolated Phase Change Material (PCM) in one of the layers of the composite surface and uses an efficient approximation algorithm to calculate average daily Energy Reduction when PCM is included.