Bathroom fan added in 2009 and was vented through the attic and out the roof to the outside. Selling the place and buyer wants it vented through the soffit in the attic to the outside. Could be expensive considering all the blown insulation in the attic and how hot is is up there. It was originally done by someone who was licensed. Is it violating code venting it up to the roof and to the outside through the attic?
Venting of a bathroom fan through the roof to the outside is correct and IRC code [303.3X] approved. Venting of a bathroom fan through the soffit is not recommended, forbidden in most places because it results in condensation buildup on the soffit’s surface and moisture migration into the attic (in case the soffit vents are close by). However, I’ve seen such installations and some jurisdictions allow it.
There might be some circumstances (in your case) dictating relocation of the existing bathroom vent, such as proximity of other roof vents (intakes or exhaust). You may want to ask the buyer’s inspector to explain his recommendation.
Please let me know.