Nashua, NH Noise from Specific Sources: HVAC & Mechanical Noise (2026)

Chapter 190 (Land Use Code) of the Nashua Revised Ordinances sets the city's explicit numeric noise standard for mechanical equipment. The operative rule: mechanical appurtenances such as heating and air-conditioning equipment may be located on the exterior portion of structures, but shall include any necessary sound buffer and/or noise attenuation equipment sufficient to reduce sound levels to 50 decibels during the daytime hours (7:00 a.m. to 8:00 p.m.) and 45 decibels during the nighttime hours (8:00 p.m. to 7:00 a.m.), measured at residential zoning district boundaries. This is the only explicit dBA cap in Nashua's noise framework - the rest of Chapter 201 (Noise) operates on the reasonableness / 50-foot audibility standard. The 10:00 p.m. / 7:00 a.m. construction-equipment night window in Chapter 128 (within 600 ft of dwellings) does not apply to permanent fixed mechanical equipment, but Chapter 190's day/night dBA split functionally creates an HVAC-specific quiet window. The Nashua City Planning Board incorporates the Chapter 190 mechanical-equipment dBA standard into the site-plan review checklist - applicants for site-plan or design review must demonstrate compliance through proposed equipment placement, screening / acoustic enclosures, or vendor noise-emission data for new commercial / multifamily HVAC installations. Existing residential single-family HVAC equipment (central air condensers, heat pumps, mini-split outdoor units) is not subject to permit-stage review but remains subject to the residential-boundary dBA cap and to Chapter 201's general disturbance standard. Common Nashua HVAC noise sources: (1) rooftop package units (RTUs) at strip-retail centers along Daniel Webster Highway, Amherst Street, and Spit Brook Road; (2) ground-mounted condensers at apartment complexes in north Nashua and along Broad Street; (3) commercial walk-in cooler / freezer compressors at restaurants throughout downtown Main Street and the Daniel Webster Highway corridor; (4) restaurant kitchen exhaust fans (which also fall under NH state mechanical code RSA 155-A and IMC adoption). Heat pumps (increasingly common in northern New Hampshire due to electrification incentives and the NH Saves residential energy program) are typically quieter than legacy central AC condensers, but condenser-fan noise can still approach the 45 dBA nighttime residential-boundary cap at close lot-line distances. NH RSA 644:2 (disorderly conduct) is the statewide backstop where mechanical-equipment noise rises to loud or unreasonable noise disturbing a person of average sensibilities. New Hampshire has no statewide HVAC-noise dB code parallel to WAC 173-60. Enforcement of the Chapter 190 50/45 dBA cap is by the Code Enforcement Department and Zoning Administrator under Chapter 190 zoning-violation procedures; Chapter 201 (Noise) enforcement is by Nashua Police.