Definition
What is blown-in insulation, and how does it work?
Blown-in insulation is loose insulation material installed via a blower machine that fans the material through a flexible hose into the cavity being insulated. The blower lives outside the home; the hose runs through a window or attic vent into the attic or up against the wall being filled. Three materials dominate the blown-in market: cellulose (recycled paper, boric-acid treated), fiberglass (spun glass fiber, lightweight), and mineral wool (less common, premium fire and sound performance).
In attics, blown-in is installed at low density — typically 1.5-2 lbs per cubic foot — to deliver the rated R per inch. Material is fanned across the joist plane to a measured depth (e.g., 17 inches of cellulose for R-60). Depth markers are installed every 300 sq ft so the post-install verification is unambiguous.
In walls, the same materials can be installed at high density via dense-pack technique — 3.5 lbs per cubic foot — which prevents settling and adds significant air-sealing properties to the cavity. Dense-pack is typically delivered through small access holes drilled in siding or drywall, with the cavity packed completely from top to bottom plate.
Honest about limitations: blown-in cellulose absorbs moisture if it gets wet — installation must occur in dry conditions and pre-existing roof or plumbing leaks must be remediated first. Loose-fill blown-in cannot be used on sloped surfaces (e.g., cathedral ceilings) without netting; spray foam or batts are typically the right call there.
We focus on retrofit projects for existing Denver homes — assessment, removal where needed, air sealing, and installation tailored to homes that are already built and lived in. New construction insulation follows a different process and is typically handled through general contractors and builders; if you're working on a new build, we can refer you to a contractor experienced with new-construction insulation scope.
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.”
Qualification signals
Who needs blown-in insulation in Denver?
Blown-in is the right material for most retrofit insulation jobs in Denver-metro homes. The strongest applications: attic top-ups over existing fiberglass batts (extremely common in 1960s-80s ranches), full attic installs in pre-1965 homes that started with no factory insulation, and wall retrofits via dense-pack in pre-1980 empty-cavity walls. If you have an attic-floor insulation gap or empty wall cavities, blown-in is almost certainly the right answer.
Where blown-in isn't the right call: cathedral or vaulted ceilings (use spray foam or batts with netting), narrow rim joists or specific air-sealing details (closed-cell spray foam excels here), and wet-prone areas like crawl spaces or basement walls (use rigid foam or closed-cell foam). The pro on your job will recommend based on the specific cavity geometry and conditions.
Materials & methods
Which blown-in insulation material is right for your Denver home?
Conservative cost ranges for typical Denver-metro projects. Specific quotes depend on your home, current insulation, and any required pre-work.
| Material | R / inch | Density (attic) | Pros | Best for |
|---|---|---|---|---|
| Cellulose | ~3.5 | 1.5-1.7 lbs/cu ft | Highest R/inch, fire-treated, recycled, sound-dampening | Most retrofit attics; dense-pack walls |
| Fiberglass | ~2.5 | 0.5-0.8 lbs/cu ft | No settling, lightweight, moisture-resistant | Trusses with weight limits; high-moisture areas |
| Mineral wool | ~3.0-3.3 | 1.5-2.0 lbs/cu ft | Best fire performance, hydrophobic, premium sound | Specialty applications, fire-priority builds |
Cost & the cost of waiting
How much does blown-in insulation cost in Denver — and what does waiting cost?
No primary source publishes a Denver-specific installed cost per conditioned square foot for cellulose or fiberglass blown-in, so this page doesn't print one; mineral wool costs more than either. Wall dense-pack retrofits price separately by exterior wall area — the free in-home estimate prices your specific project.
Cost drivers specific to blown-in: removal of compacted, pest-disturbed, or wet existing insulation adds its own cost; difficult attic access (small hatches, low-clearance attics) adds labor time; dense-pack walls require hole patching (cost depending on siding or drywall surface). The 2026 Xcel rebate programs — standard rebate plus the Whole Home Efficiency Bonus — typically reduce net cost, with Xcel's income-qualified programs available to households that qualify.
Every winter you delay a real attic-and-air-sealing upgrade on a pre-1990 Denver home, you're heating the attic through the ceiling.
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.
Cost figures are conservative ranges. The free in-home estimate gives exact numbers based on your home and required pre-work — not a range.
Denver context
What's different about blown-in insulation in Denver?
Denver's 5,280-foot elevation slightly reduces blown-in cellulose density at the time of installation due to lower atmospheric pressure on the fanning machine. Reputable installers calibrate for elevation; the post-install R-value is unaffected when the depth is verified. This is rarely an issue in practice but worth knowing if you're comparing quotes — a shop unfamiliar with high-altitude install may slightly under-deliver depth without realizing it.
Foothills-adjacent neighborhoods (Lakewood west side, Golden, Arvada west) experience higher wind-driven air infiltration than central Denver. Blown-in by itself doesn't air-seal; it must be paired with attic-plane air sealing for full performance in wind-exposed homes. Most reputable Denver crews include air sealing as a standard part of any blown-in attic job.
Cellulose's boric-acid fire treatment is particularly valuable in foothills-adjacent Denver areas where wildland-urban-interface fire risk is elevated. Fiberglass is fire-resistant but doesn't have the same boric-acid pest deterrence; cellulose tends to be the preferred material in fire- or pest-conscious foothills homes.
Most Denver blown-in jobs involve some removal of old material first — even when the existing insulation looks intact, settled cellulose or fiberglass batts often need to come out before a fresh, evenly distributed install can be guaranteed. See our insulation removal guide for when removal is required versus optional.
According to Xcel Energy, the participating-contractor symbol marks a program that requires customers to use an Xcel Energy participating contractor to install the equipment or make the improvement.
Process
How does the blown-in insulation process work?
Site prep
Crew lays drop cloths over flooring along the path from outside to attic access, sets up the blower machine outside near the chosen attic vent or window, and prepares the hose run.
Pre-blow attic prep
Air sealing of the attic plane (top plates, recessed cans, bath fan housings, attic hatch perimeter) is completed before insulation goes in. Soffit baffles are installed at the eaves to preserve ventilation.
Material setup
Cellulose or fiberglass bags are loaded into the hopper of the blower machine. The machine fluffs the material as it feeds it through the hose.
Blowing the material
Installer in the attic fans the hose evenly across the joist plane, walking from the far corner toward the access. Material is built up to the target depth based on R-value math — 17 inches of cellulose for R-60.
Depth verification
Crew measures installed depth at multiple points across the attic to confirm the target R-value is hit. Photos are taken for rebate paperwork.
Cleanup
Equipment is removed, drop cloths rolled up, and any insulation tracked into the home is vacuumed.
Rebate paperwork
Crew submits Xcel rebate forms (standard Insulation and Air Sealing Rebate, Whole Home Efficiency Bonus paperwork if measures bundle, and Xcel's income-qualified program documentation where applicable).
Rebates & credits
What rebates apply to blown-in insulation in Denver?
Blown-in insulation qualifies for the 2026 Xcel rebate programs: the Xcel Energy Insulation and Air Sealing Rebate (when meeting program R-value targets), the Xcel Whole Home Efficiency Bonus when bundled with two or more additional qualifying measures within two years, the Xcel Insulation + Air Sealing Combo Bonus when paired with a qualifying space-heating heat pump, and Xcel's income-qualified programs for qualifying households.
- Xcel Energy Insulation and Air Sealing Rebate — standard utility rebate for Xcel heating customers, paid by check after application. Work must be completed by a participating contractor, with a blower door test before and after documenting a reduction of at least 20% in CFM50.
- Xcel Whole Home Efficiency (WHE) Bonus — adds a 25% bonus on all standard rebates when three qualifying measures are completed within two years of enrolling.
- Xcel Insulation + Air Sealing Combo Bonus — a bonus when rebate-qualifying air sealing and insulation are installed before a qualifying space-heating heat pump, within two years of each other by invoice dates; the current bonus amount is set out on Xcel's own program pages.
- Xcel's income-qualified programs — eligibility is set out on Xcel's own program pages.
- Power Ahead Colorado (DRCOG) — Denver-region incentive program. Published policy funds heat pump and heat pump water heater incentives; insulation and air sealing are recommended preparation steps, not incentivized measures. Not yet live.
For current Xcel rebate amounts and program rules, see the Xcel Energy insulation and air-sealing rebates program page. For Colorado-program status (including HEAR closure and Power Ahead Colorado launch), see the Colorado Energy Office Home Energy Rebate page. Eligibility may depend on income, program funding levels, and qualifying product specifications.
Service area
Where do you provide blown-in insulation services in the Denver metro?
We connect homeowners with local insulation pros throughout Denver and the surrounding Front Range.
- Lakewood
- Arvada
- Aurora
- Wheat Ridge
- Centennial
- Englewood
- Littleton
- Westminster
- Thornton
- Park Hill
- Washington Park
- Highland
- Golden
- Broomfield
- Northglenn
Related insulation services
Get a quote
Tell Us About Your Home
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.
Frequently asked
What do Denver homeowners ask about blown-in insulation?
Should I do blown-in insulation if my home was built after 2010?
Maybe — and a build date on its own does not settle it. Post-2010 Denver homes were built to the code in force the year they went up, not today's: most attics started at R-30 to R-38, against the R-60 ceiling minimum the 2021 IECC now sets for Climate Zone 5, so a newer attic is commonly short of the current figure from day one. Walls at R-21 are a different story and usually fine. Add the 10-15 year mark, when settled batts and unsealed penetrations start showing up, and the gap widens rather than closes. If your bills and your comfort are both fine, blown-in insulation is still a judgment call about where the next dollar does the most — we'll tell you straight when we look at it.
Do you handle new construction insulation in Denver?
We focus on retrofit insulation for existing 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 construction project and need an insulation contractor, we can refer you to a partner with new-construction experience. Send us your project details through the form below and note that it's new construction in the message.
Cellulose or fiberglass — which is better?
For most Denver attic retrofits, cellulose. Higher R/inch (~3.5 vs ~2.5), better air-blocking, fire-treated, recycled, and sound-dampening. Fiberglass is the right call when the trusses can't support cellulose density, when moisture is a chronic concern (rare in Denver), or when the homeowner has a documented cellulose allergy.
Will blown-in cellulose settle over time?
Yes — typically 10-20% in the first year. Reputable installers blow extra material above the target depth to compensate, so the post-settled depth still hits the rated R-value. Ask any installer to confirm they blow to "settled R-60" or similar; it's the right way to spec the job.
Can I add blown-in over my existing insulation?
Almost always yes. Existing fiberglass batts or older cellulose can typically be left in place and topped up with new blown-in. Exceptions: wet, pest-damaged, or asbestos vermiculite (Zonolite) insulation must be removed first.
How much does blown-in attic insulation cost in Denver?
No primary source publishes a Denver-specific figure, so this site doesn't print one — the free in-home estimate prices your attic. The 2026 Xcel rebate programs — standard rebate plus the Whole Home Efficiency Bonus — typically reduce net cost, with Xcel's income-qualified programs available to households that qualify.
Is blown-in insulation a fire hazard?
Cellulose is treated with boric acid for fire resistance. Fiberglass is naturally fire-resistant.
Does blown-in work in walls?
Yes — same material at higher density (3.5 lbs/cu ft, called "dense-pack"). Dense-pack cellulose is the standard wall-retrofit method, installed via small access holes without removing drywall or siding.
How quickly can blown-in be installed?
A typical 1,500-2,000 sq ft Denver attic top-up finishes in 4-6 hours. Larger or more complex jobs (1.5-story knee walls, vermiculite removal, asbestos abatement) can run a day or two longer.
Does Xcel rebate apply to fiberglass blown-in too, or just cellulose?
Both qualify. The 2026 Xcel Energy Insulation and Air Sealing Rebate covers any blown-in material that meets program R-value targets; the rebate is based on the work outcome (R-value achieved, area covered), not the specific material.