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HF 3129

Commissioner of labor and industry required to adopt rules about unvented attics and enclosed rafter assemblies.

2025-2026 Regular Session Introduced by Joe McDonald and 1 co-sponsor

Requires unvented attic/enclosed rafter assemblies to meet R-30 insulation and U-factor ≤0.038 when heating/cooling/ventilation equipment stays inside the attic.

Author added McDonald
#buildingsandbuildingcodes #labor #employment #andlaborandindustrydepartment
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Bill Summary · HF 3129

Summary of HF 3129 (2025-2026) – Minnesota

Purpose and Intent

HF 3129 would require the Commissioner of Labor and Industry to adopt rules related to the Minnesota State Building Code, with a focus on energy efficiency and safety features. A notable provision adds explicit rulemaking to address unvented attic and unvented enclosed rafter assemblies, establishing specific insulation and air-sealing standards aligned with the Minnesota Residential Energy Code (REC) — specifically, R-30 insulation and a maximum U-factor of 0.038, provided that heating, cooling, and ventilation equipment (including ductwork) remain located inside the unvented attic.

Key Provisions and Changes

  • Amends Minnesota Statutes 2024, section 326B.106, subdivision 4 (Special requirements) to add:
    • Subsection (o): Unvented Attics and Unvented Enclosed Rafter Assemblies
    • The commissioner must adopt rules deeming unvented attics and unvented enclosed rafter assemblies insulation and air-sealing with air-impermeable insulation at R-30 and a maximum U-factor of 0.038 to meet the requirements of Section R402 of the Minnesota Residential Energy Code.
    • The insulation requirements apply only if indoor heating, cooling, and ventilation equipment (including ductwork) is located inside the unvented attic.
  • The bill otherwise largely operates within the existing framework of the State Building Code, referencing a broad array of code-related provisions (smoke detectors, doors, child care facilities, stairways, energy codes, exterior wood decks, bioprocess permits, ungraded lumber, window safety, adult changing facilities, etc.). The new provision is the primary substantive addition.

Who or What is Affected

  • Minnesota building code enforcement and administration:
    • The Minnesota Department of Labor and Industry (DLI), as the agency responsible for adopting and administering the State Building Code, would implement the new rule.
  • Homeowners, builders, and developers:
    • Projects using unvented attic or unvented enclosed rafter assemblies, where the attic is used to house heating, cooling, and ventilation equipment, would be subject to the new insulation and air-sealing standards.
  • Insulation and construction practice:
    • Requirement for air-impermeable insulation at R-30 and a ceiling/assembly U-factor not exceeding 0.038, with the caveat about equipment placement inside the attic.
  • Energy compliance:
    • Aligns with Minnesota’s Residential Energy Code (R402) requirements, potentially impacting design choices for new homes and major renovations in areas where unvented attics are planned.

Procedural and Timeline Aspects

  • Introduction and referral:
    • HF 3129 was introduced on April 7, 2025, and referred to the Committee on Workforce, Labor, and Economic Development Finance and Policy.
  • Rulemaking process:
    • The bill directs the commissioner to adopt rules using the expedited rulemaking process outlined in section 14.389, indicating a faster-than-usual rulemaking timeline for this aspect.
  • Status:
    • The document shows an action history indicating continued consideration in 2026, with a noted sponsor addition (McDonald) as of 2026-04-27, but no final enacted status provided in the text available.

Practical Implications

  • For builders and remodelers:
    • Any project involving unvented attic spaces housing mechanical equipment would need to meet the specified insulation and air-sealing standards, potentially affecting material choices, design, and costs.
  • For inspectors and code officials:
    • New compliance checks would be added to verify R-30 insulation and the U-factor cap in applicable assemblies, along with confirming that mechanical equipment remains inside the attic.
  • For energy efficiency:
    • The rule aims to improve thermal performance and reduce energy losses associated with unvented attic installations, contributing to Minnesota’s energy code goals.

If you’d like, I can provide a side-by-side comparison with current code provisions to highlight the exact changes HF 3129 would introduce.

Compiled from official sources — confirm details with the bill’s official record.

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