what is title 24?
Created to develop energy efficiency standards to ensure new and existing building achieve energy efficiency and preserve outdoor and indoor environment quality..
In 1970's it became clear that California needed to reduce the energy consumption and to reduce the impacts to the environment.   The State Legislature passed Warren Alquist State Energy Resources Conservation and Development  Act.  It grew out of a battle over power plant siting.  It  marked a historic compromise between the utilities and environmentalists. The Energy Commission  was to develop and maintain energy efficiency standards for new buildings under the Public Resources Code (Section 250402).  This section of the code is referred to as the Warren Alquist Act.
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purpose of title 24
Energy Savings
Electricity Reliability and Demand
Comfort
Economics
Environment
Global Warming

building energy efficiency standards 2013
changes to Title 24 for 2013 have been implemented as of July 1, 2014
The building envelope for Zone 12:
Roof: R-38 insulation(remains)
Roof: Radiant Barrier Required
Walls: 2 x 6 construction R-19 insulation(remains)
Floors: Slab - no insulation required
Raised foundation: R-19 insulation
Windows: Max U-Factor  0.32
Windows will have west facing restrictions of 5% glazing for prescriptive designs
Mechanical Ventilation required
Electric Resistance heaters are not allowed

building energy efficiency standards 2008
Mariposa County is split between Climate Zone 12 and 16 depending on site location. 
The building envelope for Zone 12:
Roof: R-38 insulation
Walls: 2 x 6 construction R-19 insulation
Floors: Slab - no insulation required
Raised foundation: R-19 insulation
Windows: Max U-Factor  0.40
Mechanical Ventilation required
Electric Resistance heaters are not allowed