A guide to reducing home energy costs
and increasing comfort.
Improvements   >   Attic/Wall Insulation
Quick Fact

When retrofitting insulation into existing walls, the wall cavity must be completely empty in order for the process to be benefecial.

Insulation costs a little,
but pays a lot!

Attic/Wall Insulation

Using the recommended level of insulation in your attic, walls and floor is your primary defense against heat gain in the summer and heat loss in the winter. Insulation is measured in R-values; “R” indicates resistance to heat; the higher the “R” value, the greater your home will resist the transfer of heat. Having the prescribed amount of insulation increases your home’s thermal performance while decreasing heating and cooling costs.  A properly insulated home will also reduce outside noise levels and increase comfort.

Does your home have enough insulation?

Due to the absence of energy codes, homes built in California prior to 1978 often have little or no attic, wall, and floor insulation. Starting in 1978, the California Energy Commission (CEC) began requiring new home construction to meet energy conservation standards. Known as Title 24 Energy Standards, the regulation required R-19 insulation in the attic and R-11 in the walls. These minimum standards were increased in 1985.  Unfortunately, a large percentage of California housing stock, was built prior to energy codes, and could benefit by adding more insulation.

A Safety Issue.

Cellulose insulation, used in attic and walls, has a Class 1 rating for flame spread and smoke development when tested in accordance with ASTME84.  It meets specifications set by all federal, state, and local building authorities and is tested by major testing labs including Underwriters Labratory.  Because of its fire-retardant treatment it is shown to inhibit the spread and speed of fire.  For more details about how effective Cellulose insulation can be, watch "The Big Burn" here.

How much insulation is needed?

For existing homes, attic insulation to R-30 or R-38 standards is recommended. In many homes small amounts of insulation already exist but these levels can be far below current energy standards; therefore, adding additional insulation can be a great investment. 

The average existing home’s exterior has approximately 80% wall area and when empty of insulation, can waste a substantial amount of energy. Exterior wall insulation does require the expertise of a qualified contractor. Holes are drilled and cellulose loose-fill material is pumped into the 2” x 4” wall cavity to achieve an R-13 standard. Wall insulation not only provides energy savings, but the added benefits of increasing comfort while reducing outside noise.

Insulation is made from several materials and comes in different shapes and sizes… loose-fill, batts, and rolls. Fiberglass batts and rolls are almost always installed in new home construction.  The batts are placed between the joists in the ceilings and floors and between the studs in the walls. The R-values on batts are clearly marked on the foil or paper side of the material.

When retrofitting existing structures, the following three loose-fill materials are typically installed: cellulose, rock wool and fiberglass. These products are all assigned an R-Value per inch.

To be sure you are selecting the correct insulation material for your home, follow these guidelines:

  • Material meets standards of the CPSC (Consumer Protection Safety Council)
  • Won’t damage or corrode steel, copper, aluminum, or galvanized materials
  • Odor and fungi resistant, protecting against mold and mildew
  • Fire retardant – the ability to inhibit the spread and speed of fire


Consumer Alert

When considering upgrading attic and wall insulation in existing older homes, it is highly recommended to check with your local utility provider for available cash incentive programs.  These incentives can often considerably offset your improvement cost.

Click here to check for current rabates from The Gas Company.


Top-rated against fire.

See how cellulose
compares to fiberglass
in a fire test.

When considering insulation types, sometimes using less will provide more protection and savings.

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