@Critter wrote:
but the problem arises in separating the old hvac cost from the cost basis of the house.
You cannot break out the cost of the hvac from the original cost basis once you start depreciating it.
The Treasury Department and IRS disagree with you.
Google "Partial Disposition" and Regulation §1.168(i)-8(d).
https://www.law.cornell.edu/cfr/text/26/1.168(i)-8#d
