Internal Surfaces Thermal Mass
Internal Mass, Interior Surfaces
Patrick Pease avatar
Written by Patrick Pease
Updated over a week ago

Each opaque surface within an EnergyPlus model is assigned a construction. This construction is made up of Materials that are with fully defined with Density, Thermal Performance, Specific Heat, etc. or a No Mass Material which only includes the Thermal Performance.

For ease of assigning specific Thermal Performance internal surfaces within the model are assigned a No Mass Material that reflected the defined R-value or U-value. However, including mass within the model is important to help the Heat Balance simulations resolve.

To introduce mass into the building models and improve reliability of the simulation a standard Internal Mass Material is added to each interior surface. This includes the Ceilings, Interior Floors, and Interior Walls. The thermal mass added has the follow properties

  • Thickness = 3.93 in (0.1 m)

  • Conductivity = 13.86 Btu*in/hr*ft2*R (2.0 W/m*K)

  • Density = 187.28 lb/ft3 (3000 kg/m3)

  • Specific Heat = 0.238 Btu/lb*R (1000 J/kg*K)

  • Thermal Absorptance = 0.9

  • Solar Absorptance = 0.7

  • Visible Absorptance = 0.7

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