NH Energy Code & IECC Compliance Guide for Residential Construction
New Hampshire enforces the 2015 International Energy Conservation Code (IECC) as its state energy code—adopted verbatim with minor administrative amendments. All new residential construction, additions, and major renovations must comply with mandatory provisions covering thermal envelope, mechanical systems, lighting, and verification testing. As a cold climate zone (Zone 6), NH imposes stringent requirements for insulation, air sealing, and equipment efficiency to reduce heating demand and support statewide energy goals.
NH Energy Code 2015 Adoption & Scope
New Hampshire adopted the 2015 IECC effective January 1, 2017, through RSA 155-A:3-a, administered by the NH Office of Energy and Planning (OEP). The code applies uniformly across all municipalities—no local amendments are permitted—and covers new one- and two-family dwellings, townhouses, and residential portions of mixed-use buildings. Key scope elements include mandatory prescriptive and performance paths; however, most builders use the prescriptive path due to its clarity and auditability. The code requires compliance documentation via the NH Energy Code Compliance Form (Form EC-1), submitted with building permits. Enforcement is conducted by municipal building officials trained and certified by OEP. Notably, NH does not adopt subsequent IECC editions (e.g., 2018 or 2021) as of 2024; the 2015 version remains legally binding. Exemptions are extremely limited—only agricultural buildings and certain historic renovations qualify. Design professionals must verify climate zone assignment (NH is entirely IECC Climate Zone 6A) before selecting R-values, fenestration criteria, and duct sealing requirements. Failure to submit compliant documentation risks permit denial or stop-work orders during inspections.
Envelope Requirements: Insulation, Windows & Air Sealing
In NH’s Zone 6A, the 2015 IECC mandates minimum insulation levels significantly higher than national averages: R-49 for attic/ceiling, R-21 for above-grade walls (cavity), R-10 for basement walls (continuous), and R-30 for crawl space floors. For windows and skylights, the maximum allowable U-factor is 0.32 (U-0.32), with SHGC no greater than 0.40 for north-facing glazing and up to 0.55 for south-facing to leverage passive solar gain. All exterior doors must have a U-factor ≤ 0.20. Critical to compliance is mandatory air sealing: all penetrations (plumbing, wiring, framing gaps) must be sealed with caulk, gaskets, or spray foam meeting ASTM E283 standards. Ducts located outside conditioned space must be insulated to R-8 minimum and tested for leakage (≤ 4% total duct leakage to outdoors). A continuous air barrier system—verified via visual inspection and, where required, blower door testing—is essential. Builders must document air barrier continuity on plans and provide manufacturer specs for sealants and tapes used. Non-compliant assemblies trigger rework and delay final occupancy approval.
HVAC Efficiency, Ventilation & Verification Testing
NH’s 2015 IECC sets strict HVAC efficiency thresholds: gas furnaces require ≥ 90% AFUE, heat pumps must meet ≥ 14 SEER / 8.2 HSPF (for split systems), and ductless mini-splits ≥ 15 SEER / 8.5 HSPF. All systems must include programmable thermostats with setpoint restrictions and outdoor air ventilation per ASHRAE 62.2–2013 (minimum 0.35 ACH or 7.5 CFM/person, whichever is greater). Mandatory verification includes both duct leakage testing (≤ 4% total leakage to outdoors if ducts are outside conditioned space) and a post-construction blower door test at 50 Pa pressure differential. The required air change rate is ≤ 3.0 ACH50 for new homes—a rigorous target reflecting NH’s cold climate priorities. Testing must be performed by a BPI- or RESNET-certified professional using calibrated equipment, with results submitted on Form EC-2 to the local building official. Mechanical ventilation systems must be balanced and commissioned, with airflow verified using an anemometer or flow hood. Failure to pass the blower door test necessitates targeted air sealing remediation and retesting before certificate of occupancy issuance.
Energy Audits, Utility Rebates & Compliance Workflow
While not mandated for code compliance, a pre-drywall or final energy audit is strongly recommended—and often required to access utility incentives. Eversource and Liberty Utilities (serving NH) offer rebates for high-performance features: $1.00–$2.50/sq ft for homes achieving ≤ 2.0 ACH50, $300–$1,200 for ENERGY STAR Certified Homes, and up to $1,500 for heat pump water heaters or cold-climate air source heat pumps. Eligibility requires participation in the NH Home Performance with ENERGY STAR program or equivalent third-party verification (e.g., RESNET HERS rating ≤ 55). The audit process includes infrared imaging, duct leakage testing, combustion safety checks, and whole-house modeling using REM/Rate or EnergyGauge USA. Builders must retain audit reports, equipment spec sheets, and signed compliance forms for minimum 5 years. The full compliance workflow begins with plan review using IECC-prescriptive checklists, continues through rough-in and insulation inspections, and concludes with final blower door and duct tests. Municipalities may require digital submission via NH’s ePermitting portal. Staying current with OEP bulletins—such as updated inspector training schedules or rebate program deadlines—is critical for timely project closeout.
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Does NH allow trade-offs between wall R-value and window U-factor under the 2015 IECC?
No. New Hampshire enforces the prescriptive path strictly—trade-offs between envelope components are prohibited unless using the performance path with approved software (e.g., REM/Rate) and a certified rater. Even then, the modeled design must demonstrate ≥ 10% energy cost savings versus the prescriptive baseline, verified via HERS rating.
Can a builder use fiberglass batts alone to meet R-21 in 2x6 walls per NH code?
Yes—but only if installed without compression, voids, or thermal bridging, and combined with continuous exterior insulation (R-5 minimum) to address framing losses. The 2015 IECC requires accounting for thermal bridging in Zone 6A; relying solely on cavity insulation typically fails compliance without additional sheathing-level R-value or advanced framing techniques.
Is a blower door test required for all new homes in NH, even if using the prescriptive path?
Yes. Section R402.4.1.2 of the NH Energy Code 2015 mandates a post-construction blower door test for every new dwelling unit, regardless of compliance path. The test must be conducted after drywall is complete and prior to occupancy, with results ≤ 3.0 ACH50 documented on Form EC-2 and submitted to the local building department.
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