Attic Insulation Savings Calculator (R-Value)

How to do it

1. 1
   Step 1: Open Attic Insulation Savings Calculator (R-Value) and add your input

   Type your numbers or text, add your file, or pick the options you need. Nothing is uploaded: everything stays in your browser.

2. 2
   Step 2: What Attic Insulation Savings Calculator (R-Value) does

   Estimate the heating energy and money saved by adding attic insulation.

3. 3
   Step 3: Read the result and compare

   The result appears at once. Change one value to see how the answer moves, then keep the figure that fits your case.

4. 4
   Step 4: Copy or save it

   Copy the result or download it. For an important decision, confirm it with the official source or an adviser.

About this tool

Enter the attic area, the R-value now and the new R-value, your heating degree days, the fuel and its price, and the cost of the work. The calculator shows the heat lost before and after, the saving per year and the payback time.

Heat loss

Heat lost through a ceiling per season = area × heating degree days × 24 ÷ R-value, in BTU. Raising the R-value from 11 to 38 cuts this by about 71%.

Savings

For gas the saving is the BTU saved divided by 100,000 BTU per therm and the furnace efficiency, times the price per therm. For electric resistance heat, 3,412 BTU equal one kWh.

Check

Heating degree days (base 65 °F) are published for each city. This estimates only the ceiling; air sealing often adds more savings. Recommended attic levels are R-38 to R-60 depending on climate.

Worked example

A 1,200 ft² attic going from R-11 to R-38 in a climate with 5,000 heating degree days saves 9.3 million BTU a year, about $145 of gas at $1.40 a therm and a 90% furnace. A $2,400 job pays back in about 16.6 years.

Tips for best results

Check every box before you rely on a result, because one wrong digit changes the whole answer. Use the exact figures from your payslip, bill, certificate or contract, and keep a note of the date you calculated. Rates, thresholds and rules change from time to time, so for tax, fees and legal matters treat the output as an estimate and confirm with the official source named on this page. You can run as many scenarios as you like; nothing is saved or sent, and refreshing the page clears the boxes.