Title 24 is the California Energy Code created by the California Building Standards Commission to reduce California’s energy consumption. The standards are updated periodically by the California Energy Commission to allow consideration and possible incorporation of new energy efficiency technologies and methods.
All of California is broken up into zones. The details below and the map are the current Title 24 details as of 2015.
The coastal areas of Sonoma County are in Title 24 Zone 1. These cities are Bodega Bay, Town of Bodega, Cazadero, Duncan Mills, Fort Ross, Jenner, Ocean View, Annapolis, Plantation, Sea Ranch, Soda Springs, & Stuarts Point. In zone 1 new window installations must have a U-Factor of .32 or less. Typically that will require an SB60 LowE, Argon gas and a spacer bar that does not conduct heat.
The rest of Sonoma County is in Title 24 Zone 2, which has additional requirements. From Petaluma through Santa Rosa and Windsor into Cloverdale. New window installations in Zone 2 must have a U-Factor of .32 or less and the Solar Heat Gain Coefficient aka SHGC must be at .25 or less. This will require a higher grade of LowE such as SB70, Argon Gas and a spacer that does not conduct heat.
The U-Factor measures how well a product prevents heat from escaping a home or building. The lower the U-Factor, the better a product is at keeping heat in. U-Factor is particularly important during the winter heating season.
Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat from the sun. The lower the SHGC, the better a product is at blocking unwanted heat gain. Blocking solar heat gain is particularly important during the summer cooling season.