I agree with Brian:

Insulation shield is missing. This is allowing insulation to contact the B vent. Today's requirements (G2426.4) states; 'When passing through insulated assemblies, an insulation shield shall be installed to provide clearance between the vent and the insulation material, When vents pass through attic space, the shield shall terminate not less than 2 inches above the insulation materials and shall be secured in place to prevent displacement." Have the proper shield installed to prevent the insulation from contacting the B vent.

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Darren Succasunna, NJ
www.aboutthehouseinspections.com
'The world's most plentiful ingredient is Stupidity.' (FZ)