Major Renovation Building Energy Modelling

Dear All We are currently working on a Major Renovation Building. we are confused a lot in selecting a base case for Energy Modelling 1.Is there any specific modelling guidelines for Major Renovation Buildings 2.What is the base case for Energy Modelling 3.Is ASHRAE 90.1 is a Base case for Lighting, Building Envelope, HVAC Etc. 4.Is our previous building condition is take it as Base Case for Lighting, Building Envelope, HVAC Etc. 5.We purchase some new machines now we are going to work out a Exceptional calculation in that we need to documenting systems used to perform the same function in other newly constructed facilities (three facilities built within the past five years of the project registration date) In our case Our Project is Major renovation so is it ok to take project registration date for consider three facilities built within the past five years for base caseor we take a date of major renovation start date or any other date 6.we have some already used machines and the machines are energy efficient we also done a exceptional calculation for that machines/Equipments but they are available in site before major renovation .is it acceptable It is acceptable means which date is consider for consider three facilities built within the past five years for base case