How Much Does Spray Foam Save on Heating and Cooling

Spray foam insulation is the most effective insulation type because it’s properties to act as an air sealant and insulator in one, it’s high R-value to resist and because it can be applied to the roof decking which slows the heat transfer into the home before it hits the attic.  Spray foam not only saves on your heating and cooling bills, but you also realize savings from utilizing a smaller HVAC system, the ability to save on air sealing the attic floor, an less repairs on the HVAC system over it’s life.  If you want to know how much spray foam insulation will save on your energy bills there are several factors you need to consider to get an accurate savings estimate.  The table below shows how much savings to expect from spray foam insulation for different applications.  

As APS energy auditors since 2009, Green ID has experience with spray foam in all types of homes.  The factors that influence how much spray foam insulation will save on energy bills depend on the following.

1. Age of your home will affect how much cost savings you see from spray foam insulation.  The insulation codes have changes a lot over the past 50 years and newer homes with R30 insulation will see lower cost savings after installing spray foam than homes built in the 1970’s that have 3-4 inches of insulation.  That is because well insulated homes will already be somewhat protected from the outside elements and their energy bills will be lower because their base level of insulation is already helping.  Block homes built before 1990 have no insulation in the walls so injecting spray foam into the block walls is going to have a huge benefit compared to homes with block walls built after 1990.
   1. How much will spray foam on the roof decking save? Newer homes or well insulated homes will see around a 10-15% reduction in their heating and cooling costs compared to a 20-30% reduction for older homes with little existing insulation or homes with fiberglass batt insulation.
   2. How much will spray foam in block walls save?  Homes built before 1990 with block walls will see a 15-25% reduction in their heating and cooling costs when spray foam is installed in walls that see more than 2 hours of direct sunlight.
2. Single story or two story homes.  Single story homes will benefit more from having spray foam than two story homes with typically double the attic square footage.  Existing homes with vaulted ceilings and little attic space cannot be upgraded to spray foam over the vault because it’s impossible to access unless the drywall is removed.  For vaulted ceilings an air barrier can be created between the vaulted ceiling and the accessible attic, creating a conditioned attic area with spray foam and an unconditioned attic without spray foam.  The attic with less area to apply spray foam insulation will also have lower cost savings than 100% accessible attic spaces.
3. If the existing insulation is left in the attic or removed when spray foam is applied to the roof deck.  Homeowners will save more money on their utility bills when the existing insulation is removed from the attic floor.  This is because insulation left on the attic floor with spray foam on the roof deck traps the heat inside the attic during the summer, cause the temperature to increase much higher than if no insulation is present on the attic floor.
4. The climate.  Homes in different climates can vary where heat loss and heat gain enter into the home, and then vary on how much energy can be saved with spray foam.  For example, in Phoenix, despite our 118 degree summer days, the majority of our heat gain comes in through the windows!  Not the attic, not the walls… the windows.  So it becomes impossible to save 30% on your total energy bills with spray foam on the roof decking when only 15% of your heat gain is coming from the attic space.  In Chicago, the walls are the greatest source of heat loss and so wall insulation is the best upgrade you can choose for spray foam.