Cavity wall insulation may need to be removed if it has become wet, damaged, displaced, or ineffective. Common causes include rubble or debris left in the cavity during the original construction, which can trap moisture and cause insulation to become sodden. Insulation may also require removal if it was incorrectly installed, leaving voids or uneven coverage within the cavity that allow water to track across to the internal wall leaf. Defects can also occur following window or door replacements, where changes to frames, lintels, or surrounding materials can dislodge insulation or compromise the cavity, leading to damp issues, cold spots, and reduced thermal performance.