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2021 High-Rise Building Code Changes

The following sections of the new commercial building code are now requirements:


C402.5 Air Leakage—Thermal Envelope (Mandatory)

The thermal envelope of buildings shall comply with Sections C402.5.1 through C402.5.8, or the building thermal envelope shall be tested in accordance with ASTM E 779 at a pressure differential of 0.3 inch water gauge (75 Pa) or an equivalent method approved by the code official and deemed to comply with the provisions of this section when the tested air leakage rate of the building thermal envelope is not greater than 0.40 cfm/ft2 (2.0 L/s • m2). Where compliance is based on such testing, the building shall also comply with Sections C402.5.5, C402.5.6 and C402.5.7.


Section C406 Additional Efficiency Package Options:

 C406.1 Requirements

Buildings following either ASHRAE 90.1 or IECC shall comply with at least three of the following:

  1. More efficient HVAC performance in accordance with section C406.2.
  2. Reduced lighting power density system in accordance with section C406.3.
  3. Enhanced lighting controls in accordance with section C406.4.
  4. On-site supply of renewable energy in accordance with section C406.5.
  5. Provision of a dedicated outdoor air system for certain HVAC equipment in accordance with section C406.6.
  6. High-efficiency service water heating in accordance with section C406.7.
  7. Enhanced envelope performance in accordance with Section C406.8.
  8. Reduced air-infiltration in accordance with Section 406.9.
  9. Renewable space heating in accordance with Section 406.
  10. Type IV Heavy timber construction in accordance with Section 406.11.


C406.9 Reduced Air Infiltration

Air infiltration shall be verified by whole-building pressurization testing conducted in accordance with ASTM E779 or ASTM E1827 by an independent third party. The measured air-leakage rate of the building envelope shall not exceed 0.25 cfm/ft2 (2.0 L/s x m2) under a pressure differential of 0.3 inches water column (75 Pa), with the calculated surface area being the sum of the above- and below-grade building envelope. A report that includes the tested surface area, floor area, air by volume, stories above grade, and leakage rates shall be submitted to the code official and the building owner.

Exception: For buildings having over 250,000 square feet (25 000 m2) of conditioned floor area, air leakage testing need not be conducted on the whole building where testing is conducted on representative above-grade sections of the building. Tested areas shall total not less than 25 percent of the conditioned floor area and shall be tested in accordance with this section.





C407.1.1 Energy Rating Index (ERI) for Multi-Family Buildings

 For residential units within a building up to five stories above grade plane, a HERS rater verified Energy Rating Index (ERI) score of 55 or less for each finished unit together with a completed and HERS rater verified ENERGY STAR Thermal Enclosure System Rater Checklist may be used.


 C407.5.1 ERI Documentation

  1. Prior to the issuance of a building permit, the following items must be provided to the Building Official:
  • A HERS compliance report which includes a proposed HERS index score of 55 or lower
  • A description of the unit’s energy features
  • A statement that the rating index score is “based on plans”
  1. Prior to the issuance of a certificate of occupancy, the following items must be provided to the Building official:
  • A copy of the final certificate indicating that the HERS rating index score for each unit is verified to be 55 or less
  • A completed HERS rater verified ENERGY STAR Thermal Enclosure System Rater Checklist



If you have questions about how these new code changes will affect your project, please contact our High-Rise Program lead, Andrew, at 508-974-8504 or There are also incentives and rebates available for eligible high-rise projects through Mass Save®. Click here to learn more.