Selecting Window Products: The Role of California Climate

California’s climate varies greatly, from Mediterranean to subarctic, depending on where you are exactly. Like other areas, the ocean plays a significant role in California’s temperature. It moderates temperature extremes, which makes summer significantly cooler and winter warmer, particularly along the coastal areas.

Climate is a primary consideration when selecting replacements windows in Orange County CA and other parts of the state. To get the right products for your home, you should know the recommended U-factor and SHGC according to the ENERGY STAR® Zones.

U-Factor is the degree of heat loss that occurs through the window. The lower the U-factor, the greater resistance to heat flow a window has. Now, let us look into SHGC or Solar Heat Gain Coefficient. According to the Department of Energy:

Solar heat gain coefficient (SHGC) 
is the fraction of solar radiation admitted through a window, door, or skylight — either transmitted directly and/or absorbed, and subsequently released as heat inside a home. The lower the SHGC, the less solar heat it transmits and the greater its shading ability. A product with a high SHGC rating is more effective at collecting solar heat during the winter. A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun.

California is in the North/Central and South/Central climate zones according to Energy Star. To help you pick the right replacement windows, we’ve listed the recommended U-factor and SHGC requirements for each Californian zone:

North/Central Zone U-factor (U≤0.32)

  • A low U-factor becomes more relevant with larger heating bill.
  • For superior energy performance, choose windows with a U-factor of 0.25 or lower.

North/Central Zone SHGC (SHGC≤0.40)

  • Windows with low SHGC decrease free winter solar heat gain and summer cooling demand.
  • To address high air conditioning costs and summer overheating issues, consider SHGC values of 0.30 or lower.

South/Central Zone U-factor (U≤0.35)

  • A low U-factor is beneficial for cold days when heating is required and during hot days when it is necessary to keep the heat out.

South/Central Zone SHGC (SHGC≤0.30)

  • Windows with low SHGC decrease summer cooling demand and free winter solar heat gain.

Don’t forget to check the ENERGY STAR label of the windows you plan to buy to make sure they meet the required U-Factor and SHGC for your area.

Aside from U-factor and SHGC requirements, Low-E is another important consideration for your new windows. Renewal by Andersen® of Orange County offers High-Performance™ Low-E4® glass options that provide thermal control in both cold and warm weather.

Enjoy the benefits of having the right type of Orange County windows. Get in touch with us for more information on how California’s climate can affect your window choices. With over 30 years of experience in the window replacement industry, we can offer expert recommendations that suit your requirements.

(Article Excerpt from Energy Performance Ratings for Windows, Doors, and Skylights,,  June 18, 2012 )