Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page

# Setting Solar and Visible Absorptance

I'm trying to set the solar and visible absorptance for the roof of a building. Right now, I've deduced I need to loop through the surfaces to find those with an outside boundary condition of outdoors and a surface type of RoofCeiling. Once, I single out these surfaces, how do I set their solar and visible absorptance?

Thanks.

edit retag close merge delete

Sort by ยป oldest newest most voted

Step 1) Picking up a random example file from EnergyPlus in order to better explain the solution (e.g., 1ZoneDataCenterCRAC_wPumpedDXCoolingCoil.idf) you will see that the roof is under the following object:

BuildingSurface:Detailed,
Zn001:Roof001,           !- Name
Roof,                    !- Surface Type
ROOF31,                  !- Construction Name
Main Zone,               !- Zone Name
Outdoors,                !- Outside Boundary Condition
,                        !- Outside Boundary Condition Object
SunExposed,              !- Sun Exposure
WindExposed,             !- Wind Exposure
0,                       !- View Factor to Ground
4,                       !- Number of Vertices
0.000000,15.24000,4.572,  !- X,Y,Z ==> Vertex 1 {m}
0.000000,0.000000,4.572,  !- X,Y,Z ==> Vertex 2 {m}
15.24000,0.000000,4.572,  !- X,Y,Z ==> Vertex 3 {m}
15.24000,15.24000,4.572;  !- X,Y,Z ==> Vertex 4 {m}


Step 2) ROOF31 is your roof's construction name. The object consists only of R31LAYER.

Construction,
ROOF31,                  !- Name
R31LAYER;                !- Outside Layer


Step 3) You have to look for the R31LAYER object. The answer is:

Material:NoMass,
R31LAYER,                !- Name
Rough,                   !- Roughness
5.456,                   !- Thermal Resistance {m2-K/W}
0.9000000,               !- Thermal Absorptance
0.7500000,               !- Solar Absorptance
0.7500000;               !- Visible Absorptance


This is where your solar and visible absorptance values are.

more