WHAT IS A COST SEGREGATION STUDY?

Is there any good rules of thumb to estimating the cost of a boiler?

To be brutally honest i don't care if it's at cost, below or above, I only care what it is exactly and how much. 

These methods include: Detailed Engineering Cost ApproachDetailed Engineering Cost Estimate ApproachSurvey or Letter ApproachResidual Estimation ApproachSampling or Modeling ApproachExperience or “Rule of Thumb” ApproachIt’s important to understand the differences between the approaches including which one best fits your property and the reliability of each approach.DETAILED ENGINEERING COST APPROACHThis approach compiles the costs from construction and accounting reports to build a report.

If....and this is a BIG if I know...the work was done to code, what could I reasonably expect it to cost for the inspections / rezoning process? 

Here's an article with things to consider when selecting a cost segregation company.

Looking my insurance policy it mentions that I can opt for settlement under Actual Cash Value vs Replacement Cost. 

Here's an article with FAQs including the cost of a study.

This helps determine if I would be responsible for covering those costs.

I am doing my best to accommodate and fix the insulation as well as see if there are programs in place to lower the cost. however i want to be firm with tenant as they are not compliant with paying rent because of the cost of the utilities.