Sorry for delay...
Please refer to the IRS publication 523 - http://www.irs.gov/pub/irs-pdf/p523.pdf
Improvements. These add to the value of your home, prolong its useful life, or adapt it to new uses.
Repairs. These maintain your home in good condition but do not add to its value or prolong its life. You do not add their cost to the basis of your property.
The following chart lists some other examples of improvements. <table border="0" width="390">
|Heating & Air Conditioning|
Central air conditioning
|Lawn & Grounds|
Storm windows, doors
Soft water system
Pipes and duct work
Examples. Repainting your house inside or outside, fixing your gutters or floors, repairing leaks or plastering, and replacing broken window panes are examples of repairs.
Exception. The entire job is considered an improvement if items that would otherwise be considered repairs are done as part of an extensive remodeling or restoration of your home. For example, if you have a casualty and your home is damaged, increase your basis by the amount you spend on repairs that restore the property to its pre-casualty condition.
You may find these definition a little vague - but these are the only we should rely...
I assume that the IRS agent has great experience dealing with such kind of issues and if you are trying to convince him/her to accept your interpretation of definitions without reference to precedences - that might be not the best move.
If you have been audited - you had better to have a local CPA or Enrolled Agent to represent you with the IRS.
Not only that person will instruct you for the best response, but the IRS agent will act differently if there will be a qualified representation in your case.