What is the definition of major renovation in Itemized deduction - General sales taxes?

Background: I am planning to use State and Local General Sales Tax Deduction worksheet in 1040 schedule A, itemized deduction. 

 

- Enter on line 7 any state and local general sales taxes paid on the following specified items.

- substantial addition to or major renovation of a home

 

What counts for substantial addition to or major renovation of a home? For example, is adding central air conditioning considered as "substantial addition"? Is replacing furnace a "major renovation"?