How can I insulate my attic in southern California?

Question

I live in Southern California (San Bernardino county), and I'd like to add insulation in my attic.

cathedral ceiling; 1/2 of entire roof has no attic space how do i insulate this space? the other 1/2 traditional attic space (bedrooms above this space) except there are no soffit or ventilation at the fascia, the only ventilation is at the gables (2) at each end of the house and 1 power attic fan. the only insulation i have in the attic is blown insulation about 15 inches high, how do properly insulate this attic space

Answer 1

If it was originally built correctly, the cathedral sections should already be adequately insulated... There is actually a vapor permeable membrane that is used between the decorative side you see indoors and the functional side your roofing is attached to. While this insulation is relatively thin, it serves the purpose as an air-tight barrier. The rest of the R-value (in essence) of this style of ceiling is known as thermal mass, where thicker wood or material is used to prevent temperature fluctuations. For some references to answer your questions in more detail see: http://www.applegateinsulation.com/Product-Info/Technical-Pages/249234.aspx or https://web.archive.org/web/20120629164116/http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11430