HVAC Systems for New Construction in New Hampshire

New construction in New Hampshire presents a defined window for making HVAC infrastructure decisions that affect building performance for 20 to 30 years. Unlike retrofit work, new construction allows full integration of duct routing, insulation strategy, equipment placement, and ventilation design before walls close. This page covers system types, regulatory requirements, permitting frameworks, and the structural decision factors that govern HVAC selection in NH new builds.

Definition and scope

HVAC systems for new construction refers to the complete heating, cooling, and ventilation infrastructure installed during the building phase of a residential or commercial structure — before occupancy and before the building envelope is sealed. In New Hampshire, this scope includes mechanical system specification, load calculation, duct or hydronic distribution design, equipment selection, and integration with the building's envelope performance targets.

The New Hampshire Energy Code, which adopts the International Energy Conservation Code (IECC) as its baseline, establishes minimum efficiency thresholds and envelope performance standards that directly constrain HVAC system selection in new builds. The IECC 2021 edition, referenced by the New Hampshire Office of Strategic Initiatives, sets prescriptive requirements for duct leakage, insulation R-values, and equipment efficiency ratings.

New construction HVAC differs from retrofit work in that the contractor, builder, and mechanical engineer operate simultaneously — duct routing, chase placement, and equipment room sizing are coordinated before framing is complete, rather than adapted around existing constraints.

How it works

New construction HVAC follows a sequential design-to-commissioning process with distinct phases:

1. Load calculation — A Manual J calculation (per the Air Conditioning Contractors of America standard, ACCA Manual J, 8th Edition) determines the heating and cooling loads for each conditioned zone. In NH climates with heating design temperatures as low as -3°F in northern regions (ACCA Manual J), this step is non-negotiable and forms the basis for all equipment sizing.

2. System selection — Based on load data, fuel availability, and code requirements, the mechanical contractor or engineer specifies equipment type. Options include forced-air gas or propane furnaces, boiler and hydronic systems, cold-climate heat pumps, geothermal systems, or hybrid configurations.

3. Distribution design — Ductwork design or hydronic piping layout is drafted to Manual D standards (ACCA Manual D) for forced-air systems, or equivalent hydraulic calculations for hydronic systems. Duct leakage targets for new construction under IECC 2021 are set at 4 CFM25 per 100 square feet of conditioned floor area (total leakage), per the IECC Section R403.3.

4. Permitting — The mechanical system requires a permit from the local building department before installation. NH RSA 155-A governs building code adoption and enforcement authority. Permit requirements are administered at the municipal level; NH permitting and inspections standards apply.

5. Rough-in inspection — Before insulation and drywall, a rough-in inspection verifies duct routing, equipment clearances, and fuel line placement comply with adopted codes.

6. Final inspection and commissioning — After installation, a blower door test and duct leakage test are required under IECC 2021 for new construction. Equipment is commissioned to manufacturer specifications and operational parameters documented.

Common scenarios

Single-family residential (conditioned floor area under 3,000 sq ft) — The dominant system type in NH new single-family construction is the forced-air furnace paired with central air conditioning or a heat pump. Propane is frequently used in areas without natural gas service, covering a substantial share of rural NH communities that lack pipeline infrastructure.

Energy-code-compliant all-electric builds — Cold-climate heat pumps rated for operation at -13°F (heat pump systems page) are being specified in new construction to meet increasingly stringent efficiency targets. Manufacturers including Mitsubishi, Bosch, and Daikin produce units verified under the Northeast Energy Efficiency Partnerships (NEEP) cold-climate heat pump specification.

High-performance or passive-house builds — In projects targeting Passive House Institute (PHI) or PHIUS certification, ventilation takes a central role. An Energy Recovery Ventilator (ERV) or Heat Recovery Ventilator (HRV) is required to maintain indoor air quality at tightly sealed envelope levels. Ventilation standards in these builds reference ASHRAE Standard 62.2 for residential ventilation rates.

Commercial new construction — For commercial buildings, commercial HVAC systems fall under IECC Commercial provisions and ASHRAE Standard 90.1. Equipment sizing, economizer requirements, and controls specifications are more complex. NH RSA 155-A requires that commercial mechanical systems above defined thresholds be designed by a licensed mechanical engineer.

Multi-zone and ductless mini-split configurations — In open-plan new construction or structures with irregular load zones, multi-head ductless systems allow zone-level control without central ductwork, eliminating duct leakage losses entirely.

Decision boundaries

System selection in NH new construction is governed by four intersecting constraints:

Fuel availability — Natural gas service is limited to specific utility corridors served by Liberty Utilities and Unitil. Outside those corridors, propane, oil, or electricity are the available fuel types. This geographic constraint often determines whether a gas furnace or an electric heat pump is the baseline specification.

Code compliance floor — The adopted IECC edition establishes non-negotiable minimums. Equipment with AFUE ratings below 80% for gas furnaces does not meet prescriptive compliance. Heat pumps must meet HSPF2 and SEER2 thresholds established by the U.S. Department of Energy under 10 CFR Part 430.

Licensing requirements — In NH, HVAC installation in new construction must be performed by or under the supervision of a licensed mechanical contractor. NH licensing requirements are administered by the NH Office of Professional Licensure and Certification (OPLC). Separate licensing applies to refrigerant handling (EPA Section 608 certification) and gas piping (NH licensed plumbers for gas work in many jurisdictions).

Incentive eligibility — Equipment selection affects access to rebates through Eversource NH, Liberty Utilities, and federal tax credits under the Inflation Reduction Act (IRA) Section 25C, which provides up to $2,000 for qualifying heat pump installations (IRS guidance, Energy Efficient Home Improvement Credit). Equipment must meet CEE (Consortium for Energy Efficiency) Tier specifications to qualify for utility rebates.

HVAC system sizing and insulation and building envelope performance interact directly with system selection — undersized envelope insulation raises equipment loads and may disqualify a build from certain rebate tiers.

References

• New Hampshire Office of Strategic Initiatives — Energy
• International Energy Conservation Code (IECC), ICC
• ACCA Manual J, 8th Edition — Residential Load Calculation
• ACCA Manual D — Residential Duct Systems
• ASHRAE Standard 62.2 — Ventilation for Acceptable Indoor Air Quality
• ASHRAE Standard 90.1-2022 — Energy Standard for Buildings
• Northeast Energy Efficiency Partnerships (NEEP) — Cold Climate Heat Pump Specification
• NH RSA 155-A — State Building Code
• NH Office of Professional Licensure and Certification (OPLC)
• IRS Energy Efficient Home Improvement Credit (Section 25C)
• U.S. DOE Appliance Standards, 10 CFR Part 430
• EPA Section 608 Refrigerant Management Requirements