The “best” attic insulation depends on what you’re trying to achieve, what your attic currently has, and what your budget is. This guide compares the main options honestly — not to sell you the most expensive one, but to help you identify the right one for your specific situation.
Colorado Attic R-Value Requirements: Start Here
Before comparing products, know your target. Colorado’s 2021 energy code requires:
Denver, Aurora, Fort Collins, Colorado Springs (Climate Zone 5): R-49 minimum, R-60 recommended
Boulder, higher elevation Front Range (Zone 5/6): R-49–R-60
Most Colorado homes built before 2005 have R-19 to R-30. Your goal is to reach R-49–R-60. The material that gets you there most cost-effectively depends on your attic’s configuration.
Option 1: Blown-In Fiberglass or Cellulose — Best for Most Colorado Attics
For the vast majority of Colorado homeowners upgrading an existing attic, blown-in insulation in Colorado is the right answer. Here’s why:
Installs on top of existing insulation — no removal required in most cases
Conforms to every irregular shape, around every joist, pipe, and corner
Achieves R-49 to R-60 in a single installation visit
Cost: $1.50–$2.50 per sq ft installed — most attics run $1,800–$4,500
Fiberglass: slightly less settling, better moisture resistance in attic floor applications
Cellulose: higher density, better air resistance, borate treatment deters pests
The single most important requirement: always pair blown-in insulation with attic air sealing first. Blown-in without air sealing delivers 60–70% of its theoretical performance because conditioned air continues to bypass the insulation through unsealed penetrations.
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You’re converting to a conditioned (unvented) attic assembly — HVAC equipment and ductwork live in the attic and you want them in the conditioned envelope
You need maximum R-value in limited depth (closed-cell delivers R-6–R-7 per inch vs. R-3.7 for blown-in)
You’re insulating rim joists and band joists — spray foam is the correct product here
You need both insulation and a vapor barrier in the same application (crawl space walls, basement rim joists)
Spray foam on the attic floor (rather than the roof deck) doesn’t make financial sense for R-value improvement alone — you’d pay 3x the cost of blown-in for the same R-value result. See the full comparison on our spray foam insulation in Colorado page.
Option 3: Fiberglass Batts — Best for New Construction
Fiberglass batts (the pink or yellow rolls you’re familiar with) are appropriate for:
New construction with open, accessible framing where batts can be precisely cut and fitted
Attic floors with perfectly standard joist spacing and no obstructions
Budget-constrained projects where cavity fill is the primary goal
Batts are not a good choice for adding insulation to existing attics. They require precise fitting to avoid air gaps, they can’t be added on top of existing material effectively, and they perform poorly when improperly installed (compressed batts lose significant R-value). For existing attic upgrades, blown-in is always preferable to batts.
Option 4: Pest Control Insulation (TAP) — Best for Pest-Active Properties
If your home has any history of insect activity — ants, cockroaches, earwigs, silverfish — pest control insulation in Colorado (TAP insulation) is the right choice over standard cellulose. It provides identical R-value to blown-in cellulose and installs the same way, but the borate treatment kills and deters insects permanently. The cost premium over standard cellulose is modest — typically $0.25–$0.50 per sq ft more.
The Answer: What Most Colorado Homes Actually Need
For most Colorado homeowners upgrading an existing attic from under-R-30 to R-49–R-60: the right answer is attic air sealing in Colorado (first) + blown-in insulation in Colorado (second). This combination delivers 85–90% of what spray foam would achieve at 40–50% of the cost. It’s the most cost-effective path to code-compliant attic performance for the vast majority of homes on the Front Range.
The scenarios where this changes: if you’re converting to a conditioned attic assembly, insulating rim joists, or insulating a crawl space — those applications call for spray foam. An assessment from Level Up Insulation covers all of this and makes the right recommendation for your specific home.
Attic Insulation Comparison Table
Blown-in fiberglass
R-2.2–R-2.7/inch | Cost $1.50–$2.50/sqft | Best for: adding R-value to existing attics
Blown-in cellulose
R-3.2–R-3.8/inch | Cost $1.50–$2.50/sqft | Best for: retrofit attics, pest-active homes (with TAP)
R-6–R-7/inch | Cost $3.00–$5.00/sqft | Best for: rim joists, crawl space walls, roof deck with moisture
Fiberglass batts
R-3.1–R-4.3/inch | Cost $0.75–$1.50/sqft | Best for: new construction with open framing
Ready to Fix It? Get a Free Free Attic Assessment Estimate
Level Up Insulation Co. is BPI certified, an Xcel Energy rebate partner, and serves the entire Colorado Front Range. Call us or request your free estimate online — we assess your home, explain every option, and give you a clear quote with no hidden fees and no pressure. Schedule online at Free Attic Assessment
The Best Insulation Options for Your Attic: A Homeowner’s Guide
Colorado Attic R-Value Requirements: Start Here
Option 1: Blown-In Fiberglass or Cellulose — Best for Most Colorado Attics
Contact us today for a free consultation and estimate.
Option 2: Spray Foam — Best for Conditioned Attics and Rim Joists
Option 3: Fiberglass Batts — Best for New Construction
Option 4: Pest Control Insulation (TAP) — Best for Pest-Active Properties
The Answer: What Most Colorado Homes Actually Need
Attic Insulation Comparison Table
Blown-in fiberglass
R-2.2–R-2.7/inch | Cost $1.50–$2.50/sqft | Best for: adding R-value to existing attics
Blown-in cellulose
R-3.2–R-3.8/inch | Cost $1.50–$2.50/sqft | Best for: retrofit attics, pest-active homes (with TAP)
Open-cell spray foam
R-3.5–R-4/inch | Cost $1.75–$3.00/sqft | Best for: conditioned attic roof deck
Closed-cell spray foam
R-6–R-7/inch | Cost $3.00–$5.00/sqft | Best for: rim joists, crawl space walls, roof deck with moisture
Fiberglass batts
R-3.1–R-4.3/inch | Cost $0.75–$1.50/sqft | Best for: new construction with open framing
Ready to Fix It? Get a Free Free Attic Assessment Estimate