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 R402.1.2 target for Climate Zone 5B (Denver), the gap to current state, and what the gap typically translates to in comfort and energy terms.
Your area
All Denver-metro suburbs are in IECC Climate Zone 5B.
According to the International Energy Conservation Code, “the 2021 IECC (R402.1.2) sets attic insulation minimums at R-49 to R-60 for Climate Zone 5B, which covers the Denver metro area.”
How this works
How does the r-value calculator work?
The targets come directly from IECC 2021 R402.1.2 — the ceiling-, wall-, and floor-insulation table for Climate Zone 5B (which covers all of Denver metro and the Front Range). 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.
According to the ENERGY STAR, “Climate Zone 5 homes (which includes Denver) need attic insulation rated R-49 to R-60 for optimal performance.”
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Get a Quote Based on Your Numbers
30 seconds to fill out. We'll send your inputs along with the quote request so the contractor knows what you've already calculated.
We've Got It. Here's What Happens Next.
We've got your info. A local pro is reviewing it now. Expect a call within a few hours, or by tomorrow at the latest. While you wait, here's what to look for in the quote you receive: (1) R-value target — current Colorado code is R-49 to R-60 for attics, anything less is under-spec. (2) Air sealing scope — insulation alone does nothing if air leaks aren't sealed first. (3) Rebate handling — Xcel rebate paperwork should be handled for you, not by you. (The federal IRA Section 25C credit expired in 2025 and Colorado HEAR closed for the Front Range — Xcel programs are now the active rebate stack.) (4) Removal scope — pre-1990 homes often need old insulation removed before new install. If a quote skips all four, get another quote.
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According to the Department of Energy, “adequate insulation and air sealing can reduce heating and cooling costs by 10% to 20% in typical homes.”
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 recent code, so 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.
Why R-49 minimum but R-60 recommended for attics?
R-49 is the current code minimum for new construction in Climate Zone 5B. R-60 is the retrofit recommendation because settled blown-in insulation degrades 15-20% over its lifetime, and starting at R-60 leaves you near R-49 at year 15-20 instead of dropping below code.
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 brand new and already at R-49?
Then you're meeting code on paper. 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. Until then, focus your money elsewhere.