Significant changes to the commercial provisions in 2012 IECC

Significant changes to the 2012 International Energy Conservation Code (IECC) impact architects, engineers, code officials, and other building design professionals.


Learning objectives

  1. Understand the significant changes in the commercial provisions in 2012 IECC.
  2. Learn about the newly added sections to the code. 

Figure 1: Pictured is a hospital building that has chosen on-site supply of renewable energy as the choice for compliance per newly added section C408, Additional Efficiency Package Options. Courtesy: Apollo Solutions GroupThe 2012 edition of the International Energy Conservation Code (IECC) expanded the code requirements for building systems and equipment over those of the 2009 edition to focus on conservation over the life of the building. A major formatting change was also made in that the residential and commercial provisions were split up to provide the commercial provisions in the front with a “C” preceding each section and the residential provisions in the back with a preceding “R.”

The code sections noted in this article are merely to facilitate discussion of the potential requirements that may be applicable in the 2012 IECC. This article is not intended to be a replacement for any of the referenced code/standard documents.

Section C401, Scope & Application of Commercial Energy Efficiency, has been modified to require new buildings designed using the prescriptive approach to comply with an additional efficiency package option in Section C406 and buildings designed using the performance-based approach to have energy costs ≤ 85% of the standard reference design building. Compliance with ASHRAE Standard 90.1 is still available as an option. The new section, Additional Efficiency Package Options (C406), requires new buildings to comply with at least one of three subsections: efficient HVAC performance, efficient lighting, or on-site supply of renewable energy (see Figure 1). Individual tenant spaces must comply with one of the first two unless the entire building complies with the on-site supply of renewable energy specifications or the tenant scope falls within the limitations of an alteration as noted in C101.4.3.

Lighting and efficiency

There were several changes regarding lighting, some of which increase the number of options available to designers and others that are more restrictive with the intent of increasing overall efficiency. The exception to complying with the Electrical Power and Lighting Systems (C405.1) for dwelling units within commercial buildings was made more stringent by increasing the required number of permanently installed high-efficiency lighting fixtures from 50% to 75%. Luminaries of rated power less than 100 W, equipment rooms and electrical/mechanical rooms, and daylight spaces complying with Section C405. are excluded from the Light Reduction Controls Section (C405.2.1.2) requirements.

The 5,000-sq-ft threshold on automatic time switch control devices (C405.2.2.1) was removed, and all buildings are now subject to the requirement. Occupancy sensors are now required in all meeting rooms, storage closets, and other spaces 300 sq ft or less (C405.2.2.2) and must be either manual on or controlled to automatically turn on the lighting to not more than 50% power. Additionally, daylight zone controls can no longer exceed 2,500 sq ft (C405.2.2.3), and the prescriptive approach requires compliance with new Section C405., Automatic Daylighting Controls, which requires the capability to automatically reduce lighting power in response to available daylight. Dedicated controls are now required per a new section (C405.2.3) for display and accent lighting, supplemental task lighting, and other similar specific applications.

The interior lighting power allowances in Table C405.5.2(1) have decreased for fire stations, offices, retail, and warehouses. The total interior lighting power allowance (C405.5.2) can now be determined using the building area method as well as the returned space-by-space method using newly added Table C405.5.2(2). The space-by-space method was previously known as the “tenant area or portion of building method” in the 2003 IECC before being removed in the 2006 revision.


Figure 2: The solar heat gain coefficient (SHGC) is the percent of the solar heat that is transmitted through glazing. Similarly, the visible transmittance (VT) is the percent of visible light that is transmitted through glazing. Horizontal projections abSeveral updates regarding fenestration were made that could potentially increase construction costs. The rating of visible transmittance (VT) was added to the Fenestration Product Rating section (C303.1.3) and its corresponding Table C303.1.3(3). The maximum allowable fenestration area as a percent of wall area was reduced from 40% to 30% (C402.3.1). Increased fenestration is permitted, however, with daylighting controls provided that at least 50% of the conditioned floor area is within a daylight zone and the VT is greater than or equal to 110% of the solar heat gain coefficient (SHGC). Automatic daylighting controls specified in Section C402.3 must comply with the dimming requirements in section C405.

Values were modified in Table C402.3, Building Envelope Requirements: Fenestration, and the maximum SHGC for projection factor (PF) values more than 0.2 are calculated with the newly added complementary Table C402.3.3.1, SHGC Adjustment Multipliers. Area-weighted PF values are no longer permitted to be calculated and used (C402.3.3). See Figure 2 for a description of glazing properties.

A new section was added (C402.3.2) that requires building areas of certain occupancies greater than 10,000 sq ft with ceilings greater than 15 ft to have at least 50% of the floor area as a daylight zone under skylights. Furthermore, the skylight area to daylight zone must be at least 3% with a VT of 0.40 or the skylight effective aperture must be at least 1% as determined by newly added Equation 4-1, Skylight Effective Aperture. Four exceptions were added, excluding the following:

  • Climate zones 6 through 8
  • Designed lighting power densities <0.5 W/sq ft
  • Areas where existing objects block sunlight for more than 1,500 daylight hours per year from 8 a.m. to 4 p.m.
  • Spaces where daylight zones under rooftop monitors are greater than 50% of the enclosed floor space.

Within the affected occupancies, all lighting in daylight zones is required to be controlled by multilevel lighting controls (C402.3.2.1), and skylights in most of those areas must have a measured haze factor >90%, with the exception of skylights designed to exclude direct sunlight from entering occupied spaces (C402.3.2.2).

A maximum SHGC of 0.40 in climate zones 1 to 3 for vertical fenestration ≥ 6 ft above the finished floor (C402.3.3.2) and a maximum SHGC of 0.60 in climate zones 1 to 6 for skylights above daylight zones provided with automatic daylighting controls (C402.3.3.3) are now permitted. A maximum U-factor of 0.9 in climate zones 1 to 3 and 0.75 in climate zones 4 through 8 for skylights above daylight zones provided with automatic daylighting controls is also permitted (C402.3.3.4).

Requirements and limitations on how the SHGC and VT for dynamic glazing is to be calculated and used are now specified (C402.3.3.5). Area-weighted averages are permitted to satisfy U-factor requirements within and only within each fenestration category listed in Table C402.3 (C402.3.4), potentially lowering the cost of construction.

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