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Insulate & Stay Cool

Cut Your Losses: The Importance of Insulation

Help your home keep cool in the summer and stay warm in the winter by making your home more resistance to heat transfer between the conditioned indoor space and the weather outside. Adding insulation in the ceiling and walls, as well as eliminating leaks by weatherizing or sealing your home, are the first steps to reducing your heating and cooling bills.

Efficiency: Insulation Is Key

On average, Californians spend about $96 per year for heating and cooling.1,2 According to the California Energy Commission, those costs can be cut by 30% to 50% by properly insulating an un-insulated home.3

Start Here: Choosing an Area

Insulating some areas of your home is easier and more cost-effective than others. A home energy audit can help you determine where to start. Typically you should first insulate your attic, then walls, and then tackle your basement, foundation or crawl space, if you have one.

Start at the Top: Attic Insulation

The attic is usually easiest to insulate for a single-family home, and it’s also where a lot of energy enters and leaves the building, so it’s a great place to begin.

Outside In: Insulating Walls

Adding wall insulation is more complex than adding attic insulation, and typically requires the skills of a professional contractor. Your home’s walls account for the greatest area of the building’s exterior, so adding wall insulation can be more expensive. Consult a home energy auditor or contractor to see if wall insulation is cost effective for your home.

Bottom Lines: Foundation, Basement & Crawlspace

Up to 20% of the heat in your home may escape through an un-insulated foundation.4  Consider insulating finished or unfinished basements, and crawlspaces as well.

How Much Is Enough?

The amount of insulation you should install depends on your climate, type of insulation, home construction parameters, fuel type, and energy-efficiency goals. Use the U.S. Department of Energy’s (DOE) ZIP-Code Insulation Program and R-Value Recommendations to guide you. Or, to get the most accurate recommendation, hire a professional to perform an energy audit on your home.      

Your Attic: Customized Advice

No floor: place new, un-faced batt insulation perpendicular to existing insulation to cover the joists.

Attic floor: Remove floor before adding insulation. 12 inches of insulation will be cost effective in most climates.

Finished attic with cathedral ceiling: Requires removing the roof, installing rigid material, then re-roofing. A contractor should do this. Attic insulation in this case may not be as cost effective as other weatherization measures.

No Attic: You can install insulation on the underside of the roof system rather than the floor. Any insulation work done on or around your roof should be performed by  a skilled contractor. In general, we recommend consulting with a professional before engaging in any attic insulation work on your home.

Wall Options: Best for your Home

  • Finished: Loose-fill insulation is a good choice for existing finished walls, as installation does not disturb the existing wall much.
  • Unfinished interior walls: If you’re installing a home addition, you can easily add blanket or batt insulation between the framing studs.
  • Exterior walls: If you’re replacing your home’s exterior siding, consider having a contractor install rigid board insulation.

Use & Care

Properly installing and maintaining your home’s insulation will maximize efficiency measures. Learn more about Insulation Use & Care, where to start, and how to insulate your home from high energy costs. Return to Building and Materials.

Buyer’s Guide

Before you shop for efficiency upgrades, visit the Insulation Buyer’s Guide for easy facts and figures that can help you choose the best materials for your home, needs and budget.

1 KEMA, Inc. for the California Energy Commission. (2010). 2009 California Residential Appliance Saturation Study:  Executive Summary (CEC-200-2010-004-ES). Oakland, CA: KEMA, Inc. Retrieved October 3, 2012, from http://www.energy.ca.gov/appliances...
2 Calculated using the average California household kWh usage and heating & cooling percentage from the 2009 California Residential 
Appliance Saturation Study.
3 California Energy Commission. (2012). Tighten Up Your Home.  Retrieved June 11, 2010, http://www.consumerenergycenter.org/home/tightenup/insulate.htm
4 Archambault, T., Wang, K., & Yardi, R. (2004). Home Energy Briefs, #1 Building Envelope. Snowmass, CO: Rocky Mountain Institute. http://www.rmi.org/pid217.

This program is funded by California utility customers and administered by Southern California Edison under the auspices of the California Public Utilities Commission.