Insulation wind washing is when air movement disrupts the effectiveness of insulation, typically in a building's attic or walls. This can happen when outside air penetrates the building envelope and moves through or around the insulation material. Here’s how it works:

Air Infiltration: Air can enter through gaps and openings in the exterior shell in improperly sealed homes. This can be around windows, doors, or other penetrations for utilities.

Disruption of Insulation: As air flows through these gaps, it can move through and around insulation batting or other types of insulation. The air movement effectively "washes" over the insulation.

Reduced Effectiveness: When insulation is subject to wind washing, its ability to resist heat transfer (R-value) diminishes. This is because insulation relies on trapping air within its structure to provide thermal resistance and moving air disrupts this trapped air.

Potential Consequences: The result can be increased energy costs, uneven heating and cooling in the building, and an overall decrease in comfort. It can also lead to moisture problems, as moving air can carry moisture, which may condense when it encounters cooler surfaces.

To prevent wind washing, a well-sealed vapour permeable wrap can help control both air and moisture flow, improving the overall efficiency of the building's insulation system.

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