Definition for word: Shim Space

The narrow clearance space between the window frame and the window's rough opening. To improve energy efficiency, the shim space should be sealed and filled with fiberglass or low-expanding foam insulation. It's difficult to tell if the shim space has been sealed and insulated because it's covered by interior and exterior casing.

Referrence from

A shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects. Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear.

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