On January 2, 2013

Want To Know When Your Home Insulation Will Pay For Itself?

So you have sealed air leaks in your home, replaced and updated insulation, windows and roofing, and now you are wondering, ‘When will all this energy efficiency pay back?’

Well, while the professionals at ASAP ROOFING are in favor of energy efficiency and sustainable roofing options, they are also very much aware of the bottom line. So, to help you estimate the cost effectiveness of adding home insulation, ASAP ROOFING, provides the following equation formula, which is also available at the Energy.Gov website: http://energy.gov/energysaver/articles/estimating-payback-period-additional-insulation.

The following equation helps to estimate the number of years it will take for your home insulation investment to pay for itself by way of reduced heating costs.

You can use the equation for your entire home provided that your home has a uniform R-Value. If different R-values exist for your home, you will need to calculate each R-value separately and then add the totals together. Also remember to subtract the areas occupied by windows and doors when calculating a total for wall insulation with windows and doors. If you do not have the cost of your energy source, it can be obtained either by saving your energy bill, or contacting your local energy company for a rate schedule.

You are now ready to plug your costs into the formula:

Years to Payback  =  (C(i) × R(1) × R(2) × E)   ÷  (C(e) × [R(2) – R(1)] × HDD × 24)

To calculate the payback, you must supply the following information:

C(i)  =  Cost of insulation in $/square feet. Collect insulation cost information; include labor, equipment, and vapor barrier if needed.

C(e)  =  Cost of energy, expressed in $/Btu.

  1. To calculate the cost of energy, divide the actual price you pay per gallon of oil, kilowatt-hour (kWh) of electricity, gallon of propane, or therm (or per one hundred cubic feet [ccf]) of natural gas by the Btu content per unit of fuel.
  2. To figure the price you pay per unit, take the total amount of your bills (for oil, electricity, propane, or natural gas) during the heating season, and divide it by the total number of gallons, kWh, or therms you consumed during those months. Use the following values for fuel Btu content:
    #2 Fuel Oil = 140,000 Btu/gallon
    Electricity = 3,413 Btu/kWh
    Propane = 91,600 Btu/gallon
    Natural Gas = 103,000 Btu/ccf or
    100,000 Btu/therm

E  =  Efficiency of the heating system. For gas, propane, and fuel oil systems this is the Annual Fuel Utilization Efficiency or AFUE. Typical AFUE values are 0.6 to 0.88 for oil or propane furnaces, and 0.7 to 0.95 for natural gas furnaces. Older systems are usually less efficient. Use E = 1.00 for baseboard electric systems. For heat pumps, use the Coefficient of Performance or COP for E; where E = 2.1 to 2.5 for conventional heat pumps, and E = 3.2 to 3.5 for geothermal heat pumps.

R(1)  =  Initial R-value of section

R(2)  =  Final R-value of section

R(2) – R(1) =  R-value of additional insulation being considered

HDD  =  Heating degree days/year. This information can usually be obtained from your local weather station, utility, or oil dealer.

24  =  Multiplier used to convert heating degree days to heating hours (24 hours/day).

We use HDD in our calculations because it is sufficient for homes in cold or moderate climates (which includes most of the country). For homes in hot climates, the payback calculation is more complex. To account for the full savings achievable year-round, try using a more advanced tool to calculate your energy savings such as the Home Energy Saver, created by DOE’s Lawrence Berkeley National Laboratory.


Suppose that you want to know how many years it will take to recover the cost of installing additional insulation in your attic. You are planning to increase the level of insulation from R-19 (6-inch fiberglass batts with moisture barrier on the warm side) to R-30 by adding R-11 (3.5-inch unfaced fiberglass batts). You have a gas furnace with an AFUE of 0.88. You also pay $0.87/therm for natural gas. Let’s also suppose that you supply the following values for the variables in the formula.

C(i) = $0.18/square foot

C(e) = ($0.87/therm)÷(100,000 Btu/therm) = $0.0000087/Btu

E = 0.88

R(1) = 19

R(2) = 30

R(2) – R(1) = 11

HDD = 7000

By plugging the numbers into the formula, you obtain the years to payback:

Years to Payback  =  (C(i) × R(1) × R(2) × E)   ÷  (C(e) × [R(2) – R(1)] × HDD × 24)

Years to Payback  =  (0.18 × 19 × 30 × 0.88)   ÷   ($0.0000087 × 11 × 7000 × 24)

90.288   ÷   16.077   =  5.62 years


So now you should have an approximate idea of how long it will take for your home insulation to pay for itself, but also keep in mind that at both the state and federal level, the U.S. Department of Energy incentivizes energy efficiency through a variety of programs. The resources that follow this article will direct you to a list for state and federal energy incentive programs.

And as always, ASAP ROOFING is here to help you maximize your home energy efficiency through a variety of sustainable roofing, siding and insulation options. Just visit us at www.asaproofing.com.

Written by Nick Dorotik



Nick Dorotik is the Vice President of ASAP Roofing, and manages the sales and marketing. You can find him on Google+ and twitter.


For more information about ASAP ROOFING, visit http://asaproofing.com/



The U.S. Department of Energy publishes incentives for renewables and energy efficiency for each state. The following link provides a list of Colorado Residential Incentives for homeowners:



The U.S. Department of Energy also publishes a list of Federal Incentives for Residential renewables and Energy Efficiency for homeowners. Here is a link to that list;


  • By kirk  8 Comments 

    Posted by Felix on
    • Jan 3 2013
    Damn thats a lot of math there! But the bottom line looks good. Given that the formula does not account for increasing cost of heating fuel, or for inflation. Its likely even a bit better then the math. I'll have to plug in some numbers into those equations and see what the math looks like on new windows... it seems like the level of improvement would be very extensive... however the cost of new windows is also relatively high. Lets see how the numbers pile up for the time being. I also just wanted to say that the information on this site is very good and I appreciate the fast feedback on my previous questions!
      Posted by admin on
      • Jan 3 2013
      kind of a lot of math. Hope it helps. Thanks for the feedback
    Posted by Dan Mestas on
    • Jan 4 2013
    this is awesome. how did you figure this out?
      Posted by admin on
      • Jan 5 2013
      Rigorous research.
    Posted by admin on
    • Jan 11 2013
    Great....Hope you like what you see.
    Great informative post you have added in this post with useful calculating formulas, i want to say thank for sharing such kind of informative post here. I want to say something about home insulation that insulation is a curious thing for homes and it can make our homes energy efficient. I want to say thanks for sharing this post.
      Posted by admin on
      • Feb 5 2013
      Thanks for the feedback.

    Leave a Reply

    Your email address will not be published. Required fields are marked *