Engineering Inputs

Christopher Riddell avatar
Written by Christopher Riddell
Updated over a week ago

The default R-values for roof (assembly) are referred from:

  1. ASHRAE table 5.5 when respective ASHRAE code version (2007, 2010, 2013, 2016) is selected.

  2. Table 140.3-B when respective California Title 24 code version (2016, 2019) is selected.

  3. Division B-Part 3 when respective NECB cove version (2011, 2015) is selected.

Since there are different types of material assemblies for roof which would affect what value would be used to determine the automated value, cove.tool makes that assumption for the users based on Pacific Northwest National Laboratory (PNNL) building prototypes.

  1. Roof Area: Total roof area of the building. This area can be imported using different plugins (Revit, Rhino/Grasshopper, SketchUp) that cove.tool supports or can be entered manually.

  2. Roof R-Value: This measures how effective your roof material is as an insulator. The default R-values for roof (assembly) are referred from ASHRAE table 5.5. cove.tool will automatically populate the R-values based on the location of the project assuming the Insulation Entirely above Deck roof type for all commercial building types except small offices (Attic and Other).

For example, if your project (Hospital) is in Atlanta, GA (ASHRAE Climate Zone 3A) and the energy code selected is ASHRAE 90.1 2013, the automated roof R-value (Insulation Entirely above Deck) can be seen highlighted in the image attached below:

Exporting Roof Geometry to cove.tool

In an energy model, Roof objects are defined as the insulated top surface of a conditioned space that protects against solar radiation and heat gain. Roofs are part of the thermal envelope, therefore ceilings should not be considered roofs unless they are not exposed to the outside environment. The roof object for cove.tool must only depict the cap of a thermal envelope and not expand beyond the conditioned space. For example, a canopy, cantilever, overhang, or balcony, would not be considered roof objects even if they do have identical construction properties. Instead split these elements, and export them as shading devices.

Find the Roof R-value input in the baseline page, envelope tab.

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