The fenestration (window or skylight) has a glazing U-Factor that is not valid. You must input a valid U-Factor for the fenestration. The U-factor is the coefficient of conduction (heat transfer) for the fenestration product. This value is obtained from the manufacturer of the product.
In the Building Tree, navigate to the window or skylight and click on the fenestration selection. This will take you into the Fenestration Library where you can either select another product that is valid, or you can edit the fenestration U-Factor directly.
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