Definition
What is energy audit, and how does it work?
A home energy audit, sometimes called a home energy assessment, is a diagnostic process rather than an installation. At its core is a blower door test: a calibrated fan mounted in an exterior door depressurizes the house so a technician can measure total air leakage and, often, walk the home feeling for the specific leak paths — top plates, recessed lights, penetrations — that are driving the number.
Beyond the blower door, a fuller audit typically includes a visual check of existing insulation levels against the home's attic, wall, and crawl-space assemblies, and sometimes a look at ductwork and heating/cooling equipment. Where equipment sizing is part of the scope, ANSI/ACCA Manual J is the standard used to size heating and cooling equipment to the specific home rather than by rough square-footage rules of thumb.
What an audit is not: a separately rebated project with its own dollar-for-dollar payout. It's the diagnostic step that has to happen — in one form or another — before either of Longmont's insulation rebate programs will pay out on the actual insulation or air-sealing work.
Qualification signals
Who needs energy audit in Longmont?
Anyone planning to claim either the Xcel or the Efficiency Works rebate on an insulation or air-sealing project needs this step completed first — it isn't optional paperwork, it's baked into how both programs verify eligibility.
It's also useful on its own for a homeowner who isn't sure where a home is actually losing energy — a documented blower door number and a walk-through of leak paths gives a baseline that a visual guess doesn't, even for someone not planning to pursue a rebate.
Cost & the cost of waiting
How much does energy audit cost in Longmont — and what does waiting cost?
A standalone home energy audit or blower door assessment in Longmont commonly runs a few hundred dollars, depending on home size and how much of the fuller inspection (ductwork, equipment sizing) is included. Contractors doing insulation or air-sealing work often bundle the initial blower door test into the project rather than charging for it as a separate line item.
Here's the honest part: there is no published dollar figure from either Xcel or Efficiency Works for the audit or assessment itself. Xcel's rebate requires a documented before-and-after CFM50 reduction as part of qualifying for its insulation and air-sealing payout, not as its own rebated measure. Efficiency Works requires its own assessment before it pays any incentive, again as a gate rather than a paid line item. Don't expect a rebate check for the audit step — the rebate money is on the insulation or air-sealing work that follows.
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 energy audit 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) — figures that make an accurate baseline leakage number more consequential here than in a milder climate, since the same leak rate costs more in heating dollars.
The diagnostic requirement is genuinely two-utility here. Xcel Energy's rebate applies citywide and requires a documented 20% reduction in CFM50, verified by a blower door test before and after the work. Longmont Power & Communications electric customers may separately qualify for an Efficiency Works rebate, which requires its own assessment first, before the incentive is paid — verified against Colorado's official utility-territory data, LPC serves roughly 61% of Longmont by area. Check your electric bill to know which program's diagnostic path — or both — applies to your address.
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 energy audit process work?
Initial walkthrough
Technician does a visual review of the home — existing insulation levels in the attic and walls where visible, obvious air-leak signs, and general condition of the envelope.
Baseline blower door test
A calibrated fan mounted in an exterior door depressurizes the house, and a manometer measures the home's existing air leakage rate in CFM50 — the starting number both rebate programs build on.
Leak-path walk-through
With the house depressurized, the technician walks the attic and living space identifying where air movement is strongest — top plates, recessed lights, bath fan housings, and similar penetrations.
Insulation and envelope review
Existing insulation depth and coverage are checked against the home's attic, wall, and crawl-space assemblies, giving a plain-language picture of where the home falls short.
Ductwork and equipment review (where scoped)
If HVAC sizing is part of the audit, equipment and ductwork get reviewed against ANSI/ACCA Manual J's load-calculation approach, rather than assumed from square footage alone.
Report and next steps
Findings are documented in a report — the CFM50 baseline, insulation gaps, and recommended work — that feeds directly into whichever program's application the homeowner pursues: Xcel's before-and-after CFM50 comparison, or Efficiency Works' required assessment step.
Rebates & credits
What rebates apply to energy audit in Longmont?
An energy audit doesn't carry its own rebate dollar figure from either program — it's the diagnostic prerequisite both build on. Xcel Energy's insulation and air-sealing rebates require a documented reduction of at least 20% in CFM50, verified by a blower door test before and after the work. Efficiency Works requires its own assessment first, before it will pay any insulation or air-sealing incentive, and only for Longmont Power & Communications electric customers. The rebate money is on the insulation or air-sealing work itself, not on the audit step.
Xcel Energy — applies regardless of electric utility:
- Blower door requirement, not a separate rebate line item — Xcel's insulation and air-sealing rebates require a documented reduction of at least 20% in CFM50 (cubic feet per minute at 50 pascals), verified by a blower door test before and after the work. There is no separate dollar figure paid for the test itself.
Efficiency Works — Longmont Power & Communications electric customers only:
- Assessment requirement, not a separate incentive line item — Efficiency Works requires its own assessment before it will pay any insulation or air-sealing incentive. Its published incentive sheet does not list a dollar amount for the assessment itself.
Neither program publishes a rebate figure for the audit or assessment step on its own. Treat it as the diagnostic gate to the insulation or air-sealing rebate, not as a rebated project in itself.
According to Xcel Energy, “Xcel's insulation and air sealing rebates require a documented reduction of at least 20% in CFM50 — cubic feet per minute at 50 pascals — verified by a blower door test before and after the work.”
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 home energy audits?
Should I do energy audit 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 energy audit 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 the energy audit itself get a rebate?
No — neither Xcel nor Efficiency Works publishes a dollar figure for the audit or assessment step on its own. Xcel requires a documented 20% CFM50 reduction, verified by a blower door test, as part of qualifying for its insulation and air-sealing rebate. Efficiency Works requires its own assessment before paying any incentive. Both treat the diagnostic step as a requirement, not a paid line item.
Do I need an audit even if I already know I want attic insulation?
If you want either rebate, yes in some form. Xcel's rebate requires the before-and-after CFM50 test regardless of how confident you are about what the home needs. Efficiency Works requires its own assessment first. If you're not pursuing a rebate at all, a full audit is optional, though still useful for an accurate baseline.
What's the difference between Xcel's requirement and Efficiency Works' requirement?
Xcel requires a blower door test showing at least a 20% reduction in CFM50, run before and after the insulation or air-sealing work. Efficiency Works requires its own assessment first, before the incentive is paid, and its published sheet doesn't state whether it uses the same CFM50 metric — this page doesn't assume the two are measuring leakage the same way.
How much does a home energy audit cost in Longmont?
A standalone blower door assessment commonly runs a few hundred dollars, though pricing depends on how much of the fuller inspection — ductwork, equipment sizing — is included. Many contractors bundle the initial test into an insulation or air-sealing project rather than billing it separately. The free in-home estimate gives an exact number for your home.
Does an energy audit include checking my furnace or ductwork?
It can, depending on scope. Where equipment sizing is part of the audit, ANSI/ACCA Manual J is the standard used to size heating and cooling equipment to the specific home rather than by square-footage rules of thumb. Not every audit includes this — confirm what's covered before scheduling if HVAC review matters to you.