Under the Distribution tab at the System level of the tree, you are given the option of selecting the location of the ductwork. When the location has been set to Attic, the CEC Compliance Manager requires that the total size of the attic must be at least 10% of the total square footage of the home. Without an attic of at least this size, there is insufficient space for the model to include the total volume of ductwork.
You have the option of changing the location of the ductwork by editing this input and selecting another location if your attic area does not meet this criteria.
If you think you have attic area that is 10% or more, navigate to each roof in the building tree. Review the area input for each roof. Also, click on the construction assembly and verify that you have selected a roof construction that includes an attic, and not a cathedral roof type construction.
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