Attic Insulation in Longmont, CO

Definition

What is attic insulation, and how does it work?

Attic insulation is the loose-fill or batted thermal layer installed across the floor of an unconditioned attic — directly above the ceiling drywall — to slow heat flow between the conditioned home below and the unconditioned attic above. Materials come in the same families used across the Front Range: loose-fill cellulose, loose-fill fiberglass, and batted fiberglass or mineral wool.

Loose-fill installations use a blower machine that stays outside the home; a flexible hose runs into the attic where the crew fans material evenly across the joist plane to a measured depth. Batted installations are hand-laid between joists.

Attic insulation is not a fix for moisture, ventilation, or air-leakage problems on its own. If bath fans vent into the attic, or top plates are unsealed, those need addressing first — adding insulation over an unsealed or wet attic plane can trap the underlying problem rather than solve it.

Longmont context

What's different about attic 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). Those figures drive real load calculations, not just a code checkbox — an attic running under-target loses more in a Longmont winter than the same gap would in a milder climate.

The rebate landscape is genuinely two-utility here in a way most Front Range markets aren't. Xcel Energy runs the gas-and-electric insulation rebate available to every Longmont address. 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.”

Rebates & credits

What rebates apply to attic insulation in Longmont?

Attic insulation in Longmont draws on two separate programs. Xcel Energy's citywide rebate pays a percentage of project cost for gas-heat customers against a per-measure cap — ask your contractor for the current rate. Longmont Power & Communications electric customers may separately qualify for an Efficiency Works rebate paid per square foot for flat-ceiling attic insulation, at a rate Efficiency Works publishes on its own rebates page — available only on the LPC-served portion of the city.

Xcel Energy — applies regardless of electric utility:

• Xcel Energy Insulation and Air Sealing Rebate — pays a percentage of project cost for gas-heat customers against per-measure caps; ask your contractor for the current rate. 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:

• Efficiency Works Retrofit Rebate — paid per square foot for flat-ceiling attic insulation, at a lower rate than the one most other insulation measures earn; ask your contractor for the current rate. Requires an Efficiency Works assessment first and applies only to residential electric customers of Longmont Power & Communications.

These are separate programs from separate sources. 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 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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