Opaque Construction Properties

Opaque constructions calculated values

Outside and Inside surface convective heat transfer coefficient

Outside and inside air film resistances are never given as a layer of a construction library member since they are calculated during the EnergyPlus™ simulation. In order to display approximated values in the library, worst case outside and inside surface convective heat transfer coefficients have been taken from ASHRAE 90.1-2004 Normative Appendix A. Note that these are only approximations; actual calculated values will be available after calculation.

Default value:	value taken from ASHRAE 90.1-2013 Appendix A for appropriate surface type
Min & Max:	0 < x <= 100,000
Typical Range:	0-150
Units:	W/m2; (ft2•°F•hr)/Btu

U-Factor (ASHRAE calculation)

This field describes the U-Factor or overall heat transfer coefficient. This is the rated (NFRC) value for U-factor under winter heating conditions. The U-factor is assumed to be for vertically mounted products. Although the maximum allowable input is U-7.0 W/m2 ·K, the effective upper limit of the glazing generated by the underlying model is around U-5.8 W/m2 ·K

Default value:	blank
Min & Max:	0 < x <= 100,000
Typical Range:	1 to 7 W/m2K; 0.01 to 1.0 to Btu/(hr•ft2•°F)
Units:	W/m2; Btu/(hr•ft2•°F)

Override U-factor

Set value to Yes when you would like to override the calculated U-factor. This should be done with caution as changes will have to be made to the material layers of the construction to obtain the defined value.

Radiant Later Information

Radiant source will be present after the following layer

This field is an integer that relates the location of the heat source or sink. The integer refers to the list of material layers that makeup the construction. It defines the layer after which the source is present. If a source is embedded within a single homogenous layer (such as concrete), that layer should be split into two layers and the source added between them. For example, a value of “2” in this field defines that the source is located between the second and third material layers listed in the construction description.

Calculate temperature after the following layer

This field is an integer that specifies the location for a separate temperature calculation within the construction. The integer refers to the list of material layers that makeup the construction. This temperature calculation might be important in a radiant cooling system where condensation could be a problem.

Calculate the CTF with 1 or 2 dimensions

This field is also an integer and refers to the detail level of the calculation. A value of “1” states that the user is only interested in a one-dimensional calculation. This is appropriate for electric resistance heating and for hydronic heating (when boiler/hot water heater performance is not affected by return and supply water temperatures). A value of “2” will trigger a two-dimensional solution for this surface only. This may be necessary for hydronic radiant cooling situations since chiller performance is affected by the water temperatures provided.

A few things should be noted about requesting two-dimensional solutions. First, the calculation of the conduction transfer functions (CTF) is fairly intensive and will require a significant amount of computing time. Second, the solution regime is two-dimensional internally but it has a one-dimensional boundary condition imposed at the inside and outside surface (i.e., surface temperatures are still isothermal is if the surface was one-dimensional).

Tube spacing

This field defines how far apart in meters the hydronic tubing or electrical resistance wires are spaced in the direction perpendicular to the main direction of heat transfer. Note that this parameter is only used for two-dimensional solutions.