Definition
What is duct insulation, and how does it work?
Duct insulation wraps supply and return ductwork that runs through unconditioned space — most commonly an attic or crawl space — in a fiberglass or foam wrap rated for the application, reducing how much heat the air inside the duct loses (in winter) or gains (in summer) before it reaches a room.
This is a different scope from insulating the building envelope around the duct. Attic insulation on the floor plane and duct insulation wrapped around the ducts themselves both reduce energy loss in an unconditioned attic, but they're addressing different things — the ducts carry conditioned air directly, while the attic floor separates the conditioned home below from the unconditioned space above.
Duct insulation is often scoped alongside duct sealing — closing air leaks at joints, connections, and boots with mastic or foil tape — since a well-insulated duct that's still leaking air loses much of the benefit.
Qualification signals
Who needs duct insulation in Longmont?
Homes with forced-air heating and ductwork routed through an unconditioned attic or crawl space are the clearest candidates, especially if the ducts are original to an older home and show thin, gapped, or missing insulation wrap.
Signals worth a look: rooms far from the furnace running noticeably cooler or warmer than rooms close to it, unusually high heating or cooling bills relative to home size, or visible bare or damaged duct wrap during an attic inspection.
Cost & the cost of waiting
How much does duct insulation cost in Longmont — and what does waiting cost?
Duct insulation in Longmont typically runs a few dollars per linear foot of duct wrapped, depending on duct size, accessibility, and whether sealing is done at the same time. Total project cost depends on how much duct run is exposed to unconditioned space and how easy it is to reach.
Neither Xcel Energy's rebate summary nor Efficiency Works' incentive sheet lists duct insulation as an itemized measure with its own dollar figure — this is one of the scopes neither program's published sheet names. Ask your contractor to confirm current program rules before assuming any rebate applies to a duct insulation project.
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 duct 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). Air traveling through an unconditioned attic duct run loses more heat per foot in a Longmont winter than the same duct run would in a milder climate, which is part of why duct insulation gets flagged in older homes with long attic duct runs.
The rebate landscape here is genuinely two-utility for the measures that are itemized. Xcel Energy runs the gas-and-electric insulation rebate available to every Longmont address, and Longmont Power & Communications, the city's own municipal electric utility, doesn't cover the whole city — verified against Colorado's official utility-territory data, LPC serves roughly 61% of Longmont by area. But duct insulation isn't one of the measures either program names with its own dollar figure, so the utility split doesn't change the answer here the way it does for attic or wall insulation — ask your contractor to confirm current program rules before assuming coverage.
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 5.”
Process
How does the duct insulation process work?
Duct inspection
Crew inspects accessible ductwork in the attic or crawl space, noting duct material, size, existing insulation condition, and any visible leaks at joints or connections.
Leak assessment
Joints, connections, and boots are checked for air leaks — often addressed at the same time as insulation, since sealing and insulating together gets more benefit than either alone.
Duct sealing (if scoped)
Leaks are sealed with mastic or foil tape rated for duct use — not standard cloth duct tape, which degrades over time.
Insulation wrap installation
Fiberglass or foam duct wrap rated for the application is installed around the duct exterior, with seams sealed to maintain a continuous thermal layer.
Support and clearance check
Crew confirms duct supports and hangers are intact and that the added wrap doesn't interfere with other attic or crawl space work like insulation baffles or access paths.
Documentation
Photos of completed work are provided for your records — helpful if you want to ask your utility or contractor to double-check current rebate rules for the project.
Rebates & credits
What rebates apply to duct insulation in Longmont?
Duct insulation is not one of the measures either Xcel Energy's rebate summary or Efficiency Works' incentive sheet itemizes with its own dollar figure. That's simply what each program's published sheet does and doesn't name — it isn't this page's judgment call. If you're planning duct insulation alongside attic or crawl space work that is itemized, ask your contractor to confirm which parts of the combined project, if any, a rebate would apply to.
Where duct insulation stands with both programs:
- Xcel Energy — its rebate summary itemizes attic, wall, and air-sealing measures with specific dollar caps. Duct insulation is not among them.
- Efficiency Works — its incentive sheet itemizes crawl space, basement wall, cantilever floor, exterior wall, cathedral ceiling, and attic measures by the square foot. Duct insulation is not among them.
Ask your contractor to confirm current program rules before assuming a rebate applies to duct insulation specifically — this page isn't guessing a figure that neither program has published.
According to Xcel Energy, “Xcel's insulation and air sealing rebates pay 30% of project cost for gas-heat customers, up to $500 for attic insulation, $350 for wall insulation, and $400 for air sealing, with a 1.5x multiplier for customers whose heating fuel is Xcel gas.”
According to Efficiency Works (Platte River Power Authority program, for Longmont Power & Communications electric customers), “Efficiency Works pays $1.16 per square foot for most insulation measures (conditioned crawl space, basement wall, cantilever floor, exterior wall, cathedral ceiling, conditioned attic) and $0.77 per square foot for flat-ceiling attic insulation, available only to residential electric customers of Longmont Power & Communications.”
For current Xcel rebate amounts and program rules, see the Xcel Energy insulation and air-sealing rebates page. For Efficiency Works eligibility and current incentive values, see Efficiency Works home rebates. Eligibility may depend on which electric utility serves your address, program funding levels, and qualifying product specifications.
Get a quote
Tell Us About Your Home
30 seconds to fill out. Free quote, no high-pressure follow-up.
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 model energy code for Climate Zone 5 calls for R-49 to R-60 attic insulation; ask what your contractor is quoting to. (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 duct insulation?
Should I do duct 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 duct 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 duct insulation qualify for a rebate?
Not as its own itemized measure. Xcel Energy's rebate summary names attic, wall, and air-sealing measures with specific dollar caps, and Efficiency Works' incentive sheet names crawl space, basement wall, cantilever floor, exterior wall, cathedral ceiling, and attic measures by the square foot. Duct insulation isn't on either list. Ask your contractor to confirm current program rules before assuming coverage.
What's the difference between duct insulation and attic insulation?
Attic insulation is installed across the attic floor to separate the conditioned home below from the unconditioned attic above. Duct insulation wraps the ductwork itself, which runs through that unconditioned attic space. They're different scopes addressing different heat-loss paths, and a home can need one, the other, or both.
Should I insulate or seal my ducts first?
Both are usually scoped together for a reason — a well-insulated duct that's still leaking air at the joints loses much of the benefit, and a well-sealed duct with no insulation still loses heat through the duct wall. Ask your contractor whether your specific ducts need one, the other, or both.
How much does duct insulation cost in Longmont?
Pricing runs a few dollars per linear foot of duct wrapped, depending on duct size, accessibility, and whether sealing is done at the same time. The free in-home estimate gives exact numbers based on how much duct run is exposed to unconditioned space.
Can duct insulation be done without accessing the whole attic?
Often yes, if the duct run is reasonably accessible without disturbing other insulation. But if attic insulation work is also planned, scoping both at once usually makes more sense than two separate visits.
Is duct insulation worth it if my attic is already well insulated?
Possibly, since duct insulation addresses a different heat-loss path than the attic floor does — a well-insulated attic doesn't insulate the ducts running through it. Whether it's worth prioritizing depends on how much duct run is exposed and how the rest of your system is performing; that's a good question for the free in-home estimate.