Definition
What is blown-in insulation, and how does it work?
Blown-in insulation is loose-fill material — cellulose or fiberglass — installed with a blower machine that stays outside the home while a flexible hose runs material into the attic or wall cavity. In an attic, the crew fans material evenly across the joist plane to a measured depth. The same machine and loose-fill material can also be dense-packed into an existing wall cavity through small drilled access holes, described in more detail on this site's wall insulation page — it's the same underlying technique, just a denser fill and a different cavity.
Two materials dominate blown-in work: loose-fill cellulose, made from recycled paper treated with fire retardant, and loose-fill fiberglass, made from spun glass fibers. Both are blown to a target depth or density rather than cut to fit, which is what separates blown-in from batt installation.
Blown-in is not a fix for moisture, ventilation, or air-leakage problems on its own. If an attic has an unsealed ceiling plane or an active leak, those need addressing first — blowing material over an unsealed or wet plane traps the underlying problem rather than solving it.
Qualification signals
Who needs blown-in insulation in Longmont?
Blown-in is the right call for an open, accessible attic floor with irregular joist spacing or obstructions (wiring, ductwork, low headroom) that make batt installation slow and prone to gaps — the loose material flows around obstacles that a cut batt has to be trimmed around. It's also the standard method for topping up existing attic insulation without disturbing what's already down.
For walls, blown-in (as dense-pack) applies to the same candidates described on this site's wall insulation page: pre-1990 homes with empty or settled wall cavities. If you're deciding between blown-in and batts for an open attic you're insulating from scratch, either works — the choice usually comes down to attic accessibility and whether the space is fully open or has framing that makes hand-fitting batts impractical.
Cost & the cost of waiting
How much does blown-in insulation cost in Longmont — and what does waiting cost?
This site has no single sourced per-square-foot install rate for blown-in insulation in the Longmont market. Dense-packed into a wall cavity, the drill-and-patch process is more labor-intensive than open-attic blowing, and either way price depends on current insulation level, access, and any required pre-work. The free in-home estimate gives an exact number for your home.
Both this property's rebate programs reduce net cost. Xcel's rebate is a percentage of project cost, capped by location. Efficiency Works' rebate is a flat rate per square foot, available only to Longmont Power & Communications electric customers. Whether a single project can claim both is unconfirmed: Efficiency Works' own table pairs an Xcel figure with its own and totals them, but that Xcel figure doesn't match any Xcel per-measure cap we've independently verified — ask your contractor to confirm for your specific address before assuming a combined figure.
Cost figures are conservative ranges. The free in-home estimate gives exact numbers based on your home and required pre-work — not a range.
Longmont context
What's different about blown-in insulation in Longmont?
Longmont sits at roughly 4,980 feet in IECC Climate Zone 5B, with a winter design temperature around −2°F (−10°F for boiler sizing). Whether the loose-fill goes into an attic or a wall, an under-filled cavity loses more heat in a Longmont winter than the same gap would in a milder climate.
The rebate landscape is genuinely two-utility here. Xcel Energy runs the gas-and-electric rebate available to every Longmont address, with dollar caps set by where the work happens (attic, wall) rather than what material is used. Longmont Power & Communications, the city's own municipal electric utility, doesn't cover the whole city — verified against the Colorado Geospatial Portal's own utility-territory data, LPC serves roughly 61% of Longmont by area, with Xcel, Poudre Valley REA, and United Power splitting the rest. Only LPC electric customers can access the separate Efficiency Works rebate. Check your electric bill; that's the fastest way to know which side of the line your address is on.
According to the City of Longmont Building Services, “The City of Longmont has adopted the 2024 International Codes, along with the Metro Cohort Model Code and Colorado Wildfire Resiliency Code as of July 1st, 2026.”
Process
How does the blown-in insulation process work?
Pre-work inspection
Crew inspects the target cavity — attic floor or wall — for existing insulation depth or fill, moisture or pest signs, and any obstructions before scoping material quantity.
Air sealing first
Top plates, can lights, and other attic penetrations (or, for a wall job, any accessible gaps) are sealed before material goes in — required for both the Xcel and Efficiency Works blower-door tests.
Baffle or access-hole setup
For an attic, soffit baffles go in to protect eave-vent airflow. For a wall, access holes are drilled per stud bay.
Blowing the material
Loose-fill cellulose or fiberglass is blown via a hose run from the machine outside — to a measured depth across the attic floor, or to high density inside each wall cavity.
Depth or density verification
Crew measures installed depth (attic) or checks fill density per bay (wall) to confirm coverage, and takes photos for rebate paperwork.
Rebate paperwork
Crew completes whichever program's forms apply to the address — Xcel's application, and a separate Efficiency Works application if the home is LPC electric. Each program's paperwork is filed separately; neither office handles the other's forms.
Rebates & credits
What rebates apply to blown-in insulation in Longmont?
Blown-in insulation doesn't carry a rebate line of its own — Xcel and Efficiency Works both key their dollar figures to where the material ends up, not what it's made of. Blown into an attic, the work falls under Xcel's percentage-of-cost per-measure cap (gas-heat customers; ask your contractor for the current rate) and Efficiency Works' per-square-foot flat-ceiling-attic rate. Dense-packed into a wall, it falls under Xcel's per-measure cap and Efficiency Works' per-square-foot exterior-wall rate — the same figures a batt or spray-foam job in the same location would draw on. Efficiency Works publishes both rates on its own rebates page.
Blown-in insulation doesn't have its own rebate line — both programs pay by location, not material:
- Xcel Energy — gas-heat tier applies regardless of electric utility — pays a percentage of project cost for gas-heat customers, against per-measure caps keyed to where the material is installed; ask your contractor for the current rate. A reduced tier applies to Xcel electric customers with central air conditioning whose heating fuel is not provided by Xcel Energy. Requires a participating contractor and, unless a first blower door test already finds the home tight enough by Xcel Energy's own measure, a documented 20% reduction in CFM50.
- Efficiency Works — Longmont Power & Communications electric customers only — one per-square-foot rate for flat-ceiling attic work, a different one if the material goes into an exterior wall (that second rate also covers crawl space, basement wall, cantilever floor, and cathedral ceiling locations); ask your contractor for the current rates. Requires an Efficiency Works assessment first.
These are separate programs from separate sources, and neither one prices by material. Efficiency Works' own table pairs an Xcel figure with its own and totals them, but that Xcel figure doesn't match any Xcel per-measure cap we've independently verified — confirm which applies to your address before assuming a combined figure.
According to ENERGY STAR, recommended insulation levels for retrofitting existing wood-framed buildings in Zones 6, 5, and 4C are R-60 added to the attic if the attic is uninsulated, or R-49 if it already has 3-4 inches of insulation.
For current Xcel rebate amounts and program rules, see the Xcel Energy insulation and air-sealing rebates page. Eligibility may depend on which electric utility serves your address, program funding levels, and qualifying product specifications.
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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 — ask what R-value your contractor is quoting to, in writing, and confirm the figure your permit is reviewed against with the City of Longmont's building department. (2) Air sealing scope — insulation alone does nothing if air leaks aren't sealed first, and Xcel requires a blower door test to rebate it. (3) Rebate handling — ask which programs your specific address qualifies for. Xcel and Efficiency Works are separate programs with separate paperwork, and not every address qualifies for both. (The federal IRA Section 25C tax credit ended December 31, 2025 — no federal insulation credit applies to 2026 work. Xcel Energy's insulation and air-sealing rebate remains active for its gas and electric customers. Longmont Power & Communications electric customers may separately qualify for an Efficiency Works rebate — check your bill to see which utility serves your address. Boulder County EnergySmart pays a third, income-qualified-only rebate as of January 1, 2026.) (4) Removal scope — older homes often need old insulation removed before new install. If a quote skips all four, get another quote.
Frequently asked
What do Longmont homeowners ask about blown-in insulation?
Should I do blown-in insulation if my home was built after 2010?
Probably not yet. Post-2010 homes were built to recent code — most attics started well above the pre-1990 baseline. If your bills are normal and comfort is fine, hold the money. The 10-15 year mark is when settled batts and unsealed penetrations start showing up; that's when blown-in insulation pays back on a newer home.
Do you handle new construction insulation?
We focus on retrofit insulation for existing homes. New construction insulation typically goes through your general contractor or builder, and pricing, code compliance, and timing all work differently for new builds. If you're working on new construction and need an insulation contractor, note that in the message field below and we'll refer you to a partner with new-construction experience.
Does blown-in insulation qualify for a rebate?
Not as its own category — Xcel and Efficiency Works both key their dollar figures to where the material is installed, not what it's made of. Blown-in cellulose or fiberglass in an attic falls under the same attic figures a batt job would use; dense-packed into a wall, it falls under the wall figures. See the rebate breakdown above for the actual numbers.
What's the difference between blown-in and batt insulation?
Blown-in is loose material — cellulose or fiberglass — installed by machine to a measured depth or density, flowing around obstacles like wiring and ductwork. Batts are pre-cut panels hand-fitted between framing members. Both are legitimate methods; the better fit depends on the space's accessibility and framing.
Is blown-in cellulose or blown-in fiberglass better?
Both are used across the Front Range and both fall under the same rebate figures. Cellulose is treated recycled paper and will settle 10 to 20 percent over time; fiberglass doesn't settle the same way but has its own handling and coverage considerations. Your contractor can walk through which fits your specific attic or wall.
Can blown-in insulation go into a wall, not just an attic?
Yes — dense-packed into an existing wall cavity through small drilled access holes, it's the same underlying blown-in technique at a higher density. See this site's wall insulation page for the dense-pack process in detail.
How much does blown-in insulation cost for a typical Longmont home?
This site doesn't publish a per-square-foot install rate for attic or dense-packed wall work — no Longmont-specific primary source establishes one. The free in-home estimate gives an exact number, not a range.
Does blown-in insulation require air sealing first?
It should. Blowing loose-fill material over an unsealed ceiling plane or wall cavity doesn't stop air movement, it just covers it up. Ask your contractor whether air sealing is included in the scope before material goes in.