Material Regular
 
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36 Output data in Excel

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Now we start with a new group - Surface Construction Elements. This group of objects describes the physical properties and configuration for the building envelope and interior elements. That is, the walls, roofs, floors, windows, doors for the building.

Specifying the Building Envelope
Building element constructions in EnergyPlus are built from the basic thermal and other material property parameters in physical constructions. Materials are specified by types and named. Constructions are defined by the composition of materials. Finally, surfaces are specified for the building with geometric coordinates as well as referenced constructions.

Information from the EnergyPlus Input Output Reference:

Materials

There are three material “types” which may be used to describe layers within opaque construction elements. The choice of which of these types to use is left up to the user.  The three opaque types are:

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Material:Regular

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Material:Regular-R

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Material:Air

Material:Regular is the “preferred” type of material. This requires knowledge of many of the thermal properties of the material, but it allows EnergyPlus to take into account the thermal mass of the material and thus allows the evaluation of transient conduction effects.

Material:Regular-R is similar in nature but only requires the thermal resistance (R-value) rather than the thickness, thermal conductivity, density, and specific heat. Note that using a simple R-value only material forces EnergyPlus to assume steady state heat conduction through this material layer.

Finally, Material:Air should only be used for an air gap between other layers in a construction. This type assumes that air is sufficiently lightweight to require only an R-value. In addition, since it is not exposed to any external environment, surface properties such as absorptance are not necessary.

Material:Regular

This definition should be used when the four main thermal properties (thickness, conductivity, density, and specific heat) of the material are known.

Field: Name
This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data (ref: Construction).

Field: Roughness
This field is a character string that defines the relative roughness of a particular material layer. This parameter only influences the convection coefficients, more specifically the exterior convection coefficient. A special keyword is expected in this field with the options being “VeryRough”, “Rough”, “MediumRough”, “MediumSmooth”, “Smooth”, and “VerySmooth” in order of roughest to smoothest options.

Field: Thickness
This field characterizes the thickness of the material layer in meters. This should be the dimension of the layer in the direction perpendicular to the main path of heat conduction. This value must be a positive.

Field: Conductivity
This field is used to enter the thermal conductivity of the material layer. Units for this parameter are W/(m-K). Thermal conductivity must be greater than zero.

Field: Density
This field is used to enter the density of the material layer in units of kg/m3. Density must be a positive quantity.

Field: Specific Heat
This field represents the specific heat of the material layer in units of J/(kg-K). Note that these units are most likely different than those reported in textbooks and references which tend to use kJ/(kg-K) or J/(g-K). They were chosen for internal consistency within EnergyPlus. Only positive values of specific heat are allowed.

Field: Absorptance:Thermal
The thermal absorptance field in the Material input syntax represents the fraction of incident long wavelength radiation that is absorbed by the material. This parameter is used when calculating the long wavelength radiant exchange between various surfaces and affects the surface heat balances (both inside and outside as appropriate). Values for this field must be between 0.0 and 1.0 (with 1.0 representing “black body” conditions).

Field: Absorptance:Solar
The solar absorptance field in the Material input syntax represents the fraction of incident solar radiation that is absorbed by the material. Solar radiation includes the visible spectrum as well as infrared and ultraviolet wavelengths. This parameter is used when calculating the amount of incident solar radiation absorbed by various surfaces and affects the surface heat balances (both inside and outside as appropriate). Values for this field must be between 0.0 and 1.0.

Field: Absorptance:Visible
The visible absorptance field in the Material input syntax represents the fraction of incident visible wavelength radiation that is absorbed by the material. Visible wavelength radiation is slightly different than solar radiation in that the visible band of wavelengths is much more narrow while solar radiation includes the visible spectrum as well as infrared and ultraviolet wavelengths. This parameter is used when calculating the amount of incident visible radiation absorbed by various surfaces and affects the surface heat balances (both inside and outside as appropriate) as well as the daylighting calculations. Values for this field must be between 0.0 and 1.0.

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