When combined, the material thermal properties define the following characteristics for each construction type.
A series of conduction time factors for a wall or roof material over a 24-hour period is called a conduction time series (CTS). Chapter 30 of the ASHRAE 2005 HoF contain tables of CTS values for many different wall and roof constructions. The Engine in Revit MEP is able to derive an unlimited number of wall and roof CTS schedules based upon the thermal properties of each material type that makes up the wall or roof.
Ceilings, partitions, and doors do not require CTS schedules for the cooling load calculations.
The R-value of a material or construction represents its thermal resistance or heat loss retardation. The U-value is the reciprocal of R-value. The total U-value of a construction can be derived by adding the reciprocal of the R-values of the individual materials that make up the construction. The R-value (or U-value) of each material is dependent upon the properties of the material, itself, and the thickness of the material. In Revit MEP, construction types for the walls, roofs, doors, and floors are selected for each space either in the space Instance Properties dialog or in the Heating and Cooling Loads dialog.