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Attic Insulation Savings Calculator

Attic insulation + air-sealing savings

What could an attic insulation upgrade save?

Start with your existing attic insulation, including R-10, and compare a final value of R-49 or R-60. See insulation-only savings first, then the additional air-sealing estimate and complete package total. All figures use the square footage you enter directly.

Planning estimate, not a guaranteed bill reduction. Uses published Rocky Mountain Power Utah standard residential and Enbridge Gas Utah GS rates verified October 23, 2026. Choose custom rates for another utility, time-of-use or solar plan.

Your project and utility bills

Pleasant Grove climate: 5,005 heating / 1,187 cooling degree days per year (base 65°F). Adjust these in the settings for another location.

Enter the attic floor area above conditioned rooms. The calculator uses this number directly.
Use your last 12 bills ÷ 12. Enter 0 if you do not use gas.
Use your last 12 bills ÷ 12, not only a summer bill.
Depths are approximate and vary by material and settling. Have the existing R-value assessed.
Adds R-22 to your existing R-38.

Air sealing is included in Interwest’s upgrades. Results distinguish insulation savings from the assumed air-sealing benefit, then add them for the package total. The 10-year projection assumes utility energy prices rise 4% per year.

Equipment, rates and air-sealing assumptions
90% is an assumption; use your equipment rating.
Illustrative default. Use SEER, not EER.

Climate default: NOAA Pleasant Grove station USC00426919, 1991–2020 normals: 5,005 heating and 1,187 cooling degree days, base 65°F. Other locations differ. Custom annual totals keep the Pleasant Grove seasonal pattern.

Air-sealing savings assumptions

Air sealing is included in every option. Without an energy audit, savings use the illustrative assumptions below. Actual leakage reduction can be lower or higher; adjust with professional audit information. These are not measured Interwest job results.

0.4 is an illustrative starting assumption. This is natural ACH, not a blower-door ACH50 reading.
20% is an attic-sealing scenario informed by ENERGY STAR’s modeling assumptions, not a guaranteed result. It does not mean 20% lower bills.

No email or bill uploads required. Calculations run in your browser.

Compare the insulation upgrade

Insulation-only monthly savings

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Enter your attic area and bills, then compare final R-49 and R-60.

Default equipment: 90% gas furnace and SEER 13 central AC. Open settings to match your home.

Insulation already in place affects the value of adding more. An assessment can check coverage, air leaks and the appropriate upgrade for your attic.

Request an attic assessment

Which square footage should I enter?

Use the total attic floor area being upgraded above conditioned rooms. Do not include an unheated garage or add basement floor area. The number is used directly as the insulation area.

Your utility bill includes appliances, water heating and other uses that attic insulation will not eliminate. Bills show savings relative to current spending; they do not set the energy price. Insulation savings and an illustrative air-sealing improvement are shown separately, with a combined package total.

For other utility plans—including municipal electricity, time-of-use and solar—choose custom rates in the settings. This simple model does not simulate hourly solar exports or time-of-use schedules.

Need help measuring the attic or choosing an upgrade? Request an attic assessment.

How the estimate is calculated

Heating energy saved = attic area × 24 × heating degree days × (1 ÷ existing R-value − 1 ÷ final R-value), divided by heating efficiency. Natural gas is converted using 100,000 BTU per therm. This uses the same simplified nominal R-value heating approach as the CIMA calculator linked below. Cooling uses cooling degree days and SEER separately. The insulation component excludes framing bridges, installation defects, other ceiling layers and solar roof heating. Air-sealing savings are calculated separately and added once.

For air sealing, the entered area × average ceiling height provides a simplified volume proxy. It is not a measurement of the entire home’s volume. The example starts at 0.4 natural air changes per hour and assumes 20% less leakage after attic sealing. Sensible heat savings use volume × reduction in natural air changes × 0.018 BTU per cubic foot per °F × degree days × 24 hours, adjusted for equipment efficiency. The standard-air approximation does not model humidity, altitude, wind, mechanical ventilation changes or seasonal infiltration effects. An audit is needed for a home-specific prediction.

Monthly climate normals allocate energy savings between the utilities’ summer and winter periods. Standard rate ranges use the two published usage tiers; custom rates use one entered energy price throughout the year. This is an educational model, not a utility-endorsed prediction or an energy audit.

Choose the final total R-value: R-49 or R-60. Insulation added equals the final R-value minus your starting R-value. If the starting and final values are both R-49, insulation-only savings are zero; the air-sealing estimate remains separate. This comparison does not establish rebate eligibility.

Understand R-38, R-49 and R-60 · Explore attic insulation service

Rebates are one-time incentives, separate from the utility savings shown here. See Utah insulation rebate requirements and our cost guide.

Utility rates and technical references

Rates verified October 23, 2026. Published snapshot, not a live utility feed. Standard electric rates include applicable usage-based adjustments; local taxes and fixed customer charges are excluded from savings. Rate changes require review.

  • Rocky Mountain Power Utah price summary — effective September 25, 2026, Schedule 1 standard rates and listed adjustments. The Schedule 92 adjustment used here runs through December 31, 2026.
  • Enbridge Gas Utah tariffs — GS volumetric summer/winter rates, revised June/July 2026; 1 Dth = 10 therms.
  • NOAA Pleasant Grove climate normals — station USC00426919, 1991–2020, page 1; annual HDD65 5,005 and CDD65 1,187. Rounded monthly values are scaled to the entered annual totals.
  • U.S. Department of Energy insulation savings equations — Appendix E.7. Our simplified model uses nominal R-values; it is not a calibrated whole-house simulation.
  • CIMA insulation savings calculator — the insulation-only heating component matches when area, degree days, R-values, gas price and furnace efficiency match. Interwest’s totals also include an assumed air-sealing improvement. CIMA’s separate 10-year result assumes 10% annual fuel-price increases; this calculator uses a fixed 4%.
  • ENERGY STAR air-sealing upgrade assumptions — includes a 20% infiltration-reduction scenario for attic sealing. Our starting natural leakage and ceiling height are illustrative assumptions, not ENERGY STAR ratings or verified Interwest performance.