The calculator
Run the r-value calculator
Pick which area of your home you're evaluating, your home's era, and current insulation depth. The calculator returns the IECC 2021 target for Climate Zone 5B (Denver), the gap to current state, and what the gap typically translates to in comfort and energy terms.
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According to the International Energy Conservation Code, the 2021 IECC sets a minimum ceiling insulation R-value of R-60 in Climate Zone 5 under Table R402.1.3, and Section R402.2.1 allows R-49 to satisfy that requirement only where the full height of uncompressed R-49 insulation extends over the wall top plate at the eaves.
How this works
How does the r-value calculator work?
The targets come from the 2021 IECC ceiling-, wall-, and floor-insulation table for Climate Zone 5, which covers all of Denver metro and the Front Range (Denver is 5B). The attic figure is R-60; R-49 satisfies it only where the full height of uncompressed insulation extends over the wall top plate at the eaves. Current-state estimation uses the era and visible-depth inputs as rough proxies; the free in-home estimate gives an exact measurement.
Calibrated against the IECC 2021 IRC code reference and Colorado building code as of May 2026.
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According to ENERGY STAR, recommended insulation levels for retrofitting existing wood-framed buildings in Zones 6, 5, and 4C are R60 added to the attic if your attic is uninsulated, or R49 if you already have 3-4 inches of insulation.
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We've Got It. Here's What Happens Next.
We've got your info and are routing it to a local pro. When they call, here's what to look for in the quote you receive: (1) R-value target — the 2021 IECC sets a ceiling minimum of R-60 in Climate Zone 5 (Table R402.1.3); R-49 qualifies only where uncompressed insulation extends full-height over the top plate at the eaves. (2) Air sealing scope — insulation and air sealing work together; sealing the leaks first is what lets the insulation do its job. If a quote skips both, get another quote. The federal IRA Section 25C tax credit ended December 31, 2025, and Colorado's HEAR single-family program is now closed for both Region 1 (the Front Range) and Region 2. Xcel Energy programs are the ones still paying on Denver-area insulation projects in 2026.
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According to ENERGY STAR's Seal and Insulate program, “EPA estimates that homeowners can save an average of 15% on heating and cooling costs (or an average of 11% on total energy costs) by air sealing their homes and adding insulation in attics, floors over crawl spaces and basements.”
Frequently asked
What do Denver homeowners ask about this calculator?
Should I use this calculator if my home was built after 2010?
Possibly — but interpret the output cautiously. Post-2010 Denver homes were built to the code edition in force at the time, which set a lower ceiling minimum than the R-60 the 2021 IECC requires — so a newer home can be code-legal as built and still sit short of today's target. Most calculator scenarios assume pre-1990 baselines and may overstate the project value for newer homes. If your bills are normal and your comfort is fine, the honest answer is usually: hold the money. The 10-15 year mark is when even code-compliant homes start showing settled batts.
Do you handle new construction insulation?
We focus on retrofit insulation for existing Denver homes. New construction insulation typically goes through your general contractor or builder, and the process is different — pricing structures, code compliance steps, and project timing all work differently for new builds. If you're working on a new build, we can refer you to a partner with new-construction experience.
Is the attic target R-49 or R-60?
R-60. The 2021 IECC sets R-60 for ceilings in Climate Zone 5, which covers Denver. R-49 satisfies that requirement only under a narrow allowance — where the full height of uncompressed R-49 insulation extends over the wall top plate at the eaves. R-49 was the minimum under the 2018 edition, which is why it still turns up in older quotes. Separately, ENERGY STAR recommends adding R-60 to an uninsulated attic in this zone, or R-49 if you already have 3 to 4 inches.
How do I tell what R-value my current insulation actually is?
Visible depth × R-value-per-inch. Loose-fill cellulose is ~3.5 R/inch; loose-fill fiberglass ~2.5 R/inch; fiberglass batts vary by product but a 6-inch batt is typically R-19. The free in-home estimate measures depth and identifies material — DIY-able with a tape measure if you can safely access the attic.
Does Climate Zone 5B mean my whole house, or just specific areas?
All of Denver metro and the Front Range fall in Climate Zone 5B for IECC purposes. Different areas of your home (attic, wall, floor, crawl) have different R-value targets within the same climate zone, but you don't need different climate-zone references for different rooms — it's all 5B.
What if my home is newer and already at R-49?
Then you are at the level the 2018 code required, and at the 2021 requirement only if that insulation runs full height over the top plate at the eaves. Otherwise you are 11 points short of R-60. Either way, settled insulation and unsealed attic-plane penetrations show up in the 10-15 year window, which is when even code-compliant homes start needing top-ups plus targeted air sealing.