Which R-value of insulation would be used most often to conform with the State Energy Commission requirements, when insulating an attic during new construction?

Using an R-value of R30 for attic insulation aligns with the California State Energy Commission (CEC) requirements, particularly for new residential construction. The R-value measures the insulation's thermal resistance, which indicates how well the material can resist heat flow. A higher R-value means better insulating properties, which is crucial in California's climate to enhance energy efficiency and reduce heating and cooling costs.

In many areas of California, especially in zones with more extreme temperatures, an R-value of R30 is often recommended or required to meet both building codes and energy efficiency standards. This level of insulation helps to ensure that homes remain comfortable throughout the year while also minimizing energy consumption.

The other options generally fall short of current standards; R11 and R19 may have been suitable in the past or for specific applications, but they typically do not provide the necessary level of insulation for attics in new construction as per the latest CEC guidelines. Therefore, R30 represents the standard that not only meets but often exceeds the requirements for effective insulation in attics, contributing significantly to energy savings and comfort in residential buildings.