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.
Worth separating two things that share the word "audit" here. The blower door reading Xcel wants before an insulation or air-sealing rebate is a condition of qualifying — 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 work. A home energy audit is also listed on Xcel's own rebate summary as its own category with its own criteria, which is a separate question from the insulation rebate this page is mostly about.
Qualification signals
Who needs energy audit in Longmont?
Anyone planning to claim the Xcel rebate on an insulation or air-sealing project needs a blower door reading behind it — but not necessarily a full audit, and not necessarily a new one: Xcel's product write-up asks for that reading on any project that has not already had a recent home energy audit that included one, so a recent audit can carry the step rather than starting it over. Xcel's Whole Home Efficiency page names two ways into that program rather than one — a Home Energy Squad Plus visit, or a Blower Door or Infrared Home Energy Audit by a qualified participating contractor — so an audit is not the single door there either. Efficiency Works is a separate program with its own rules: it requires its own assessment first, before it will pay any insulation or air-sealing incentive.
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: the blower door reading your insulation rebate depends on is not itself a rebated measure. Xcel's product write-up treats the blower door reading as a condition of qualifying rather than its own rebated measure: one before the work, and unless that reading already finds the home tight enough by Xcel Energy's own measure, another after air sealing documenting at least a 20% reduction in CFM50 before the attic or wall insulation rebate is reachable. Those two insulation measures carry R-value conditions in addition. Efficiency Works requires its own assessment before it pays any incentive, again as a gate rather than a paid line item. A home energy audit is a separate matter: Xcel lists home energy audits on its own rebate summary as their own category, with their own criteria — see Xcel's rebate page for what it currently pays and who qualifies.
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 its product write-up runs the blower door before the work and, unless that first reading already finds the home tight enough by Xcel Energy's own measure, again after air sealing to document at least a 20% reduction in CFM50 — the gate the attic and wall insulation rebates sit behind, with those measures' R-value conditions applying in addition. 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 the Colorado Geospatial Portal's own 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 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 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 baseline CFM50 reading and the post-work comparison it calls for unless that baseline already shows the home tight enough, or Efficiency Works' required assessment step.
Rebates & credits
What rebates apply to energy audit in Longmont?
The blower door reading both programs build on is a prerequisite, not a rebated measure in itself — though Xcel does list home energy audits separately on its own rebate summary, with their own criteria. Xcel Energy's product write-up requires a blower door reading before the work and, unless that reading already finds the home tight enough by Xcel Energy's own measure, air sealing and a second reading documenting at least a 20% reduction in CFM50 before the attic or wall insulation rebate can be claimed; those two insulation measures carry R-value conditions as well. 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 product write-up requires a blower door reading before the work and, unless that reading already finds the home tight enough by Xcel Energy's own measure, air sealing and a second reading documenting at least the 20% reduction in CFM50 Xcel Energy requires (cubic feet per minute at 50 pascals) before the attic or wall insulation rebate can be claimed; those two insulation measures carry R-value conditions in addition. The reading itself is a condition of qualifying, not a rebated measure.
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.
Two different things share the word “audit” here. The blower door reading Xcel requires before it will pay an insulation or air-sealing rebate is a condition of qualifying, not a rebated measure — treat it as the diagnostic gate to the rebate. A home energy audit is listed separately on Xcel's own rebate summary, with its own criteria. Check Xcel's rebate page for current amounts and eligibility before assuming either way.
According to Xcel Energy, its Insulation and Air Sealing product write-up requires a pre-improvement blower door test in CFM 50 — cubic feet per minute at 50 pascals — on any project that has not already had a recent home energy audit that included one; unless that test finds the home already tight enough by Xcel Energy's own measure, air sealing is required and a post-improvement test must show at least a 20% reduction in air leakage before attic or wall insulation can qualify for a rebate, and the insulation measures carry R-value conditions of their own beyond the blower-door result.
According to Efficiency Works (Platte River Power Authority program, for Longmont Power & Communications electric customers), Efficiency Works pays a per-square-foot incentive for most insulation measures (conditioned crawl space, basement wall, cantilever floor, exterior wall, cathedral ceiling, conditioned attic) and a separate per-square-foot rate for flat-ceiling attic insulation, available only to residential electric customers of Longmont Power & Communications, with the current rates published on its own incentive sheet.
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.
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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 — 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 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?
Two separate things get called the audit here. Xcel lists home energy audits on its own rebate summary as their own category with their own criteria — check Xcel's rebate page for current amounts and who qualifies. That is different from the blower door reading Xcel requires as a condition of the insulation and air-sealing rebate: Xcel's product write-up makes a documented 20% CFM50 reduction the gate on the insulation side of its insulation and air-sealing rebate as well as on the air-sealing side, unless the baseline reading already finds the home tight enough by Xcel Energy's own measure, and the two insulation measures carry R-value conditions in addition. Efficiency Works requires its own assessment before paying any incentive. Both treat that 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 — and a recent audit may already have covered it. Xcel's write-up asks for a blower door reading before the work on any project that has not already had a recent home energy audit that included one, so a recent audit with a blower door test can carry that step rather than starting it over. Either way, that reading is what decides whether the home is already tight enough by Xcel Energy's own measure or has to hit a documented CFM50 reduction first for the insulation rebate. 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's product write-up runs a blower door reading before the work and, unless that reading already finds the home tight enough by Xcel Energy's own measure, a second one after air sealing showing at least a 20% reduction in CFM50 — the gate the attic and wall insulation rebates sit behind, with R-value conditions on those two measures in addition. 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.