2006 IECC

The 2006 changes (compared to IECC 2003), include:

• New climate basis: - strictly geographical (no more HDD)

                                             - fewer zones (more homogeneity within jurisdictions)

                               - better climate coverage (zones based on more than HDD)

                                             - Residential / Commercial use the same climate zones

• Single family and multy family consolidated
• Envelope requirements independent of window-wall ratio (except in perfortmance path)
• Performance path closer to prescriptive
• New "trade-off" limits for glazing U-Factor and SHGC

Chapter 1: ADMINISTRATION

Regulatory Requirements (102.1.3)

U-Factors and Solar Heat Gain Coefficient (SHGC) of fenestration products (windows, doors and skylights) shall be determined in accordance with NFRC 100 and NFRC 200 respectively, by an accredited, independent laboratory, and labeled and certified by the manufacturer. Products lacking such labels, shall be assigned default values (Table 102.1.3: 1, 2 and 3). The default values typically do not give full credit for energy efficient performance.

Chapter 4: RESIDENTIAL ENERGY EFFICIENCY

Fenestration Air Leakage( 402.4.2. - mandatory):

Air leakage requirements are set at 0.3 cfm/sf for windows and sliding doors (cubic feet per minute per square foot of window area) and 0.5 cfm/sf for swinging doors. Fenestration systems must be tested in accordance with NFRC 400 or AAMA/WDMA/CSA 101/I.S.2/A440, by an accredited, independent laboratory and listed and labeled by the manufacturer.                          Exceptions: Site built windows, skylights and doors.

Prescriptive requirements (402.1.1) - by climate zone are shown below:

Table 402.1.1 in the 2006 IECC

Click here to see the corresponding climate map.

Total UA alternative (402.1.4)

If the total building thermal envelope UA (sum of U-factor times assembly area) is less than or equal to the total UA resulting from using the U-factors in Table 402.1.3 (see below, multiplied by the same assembly area as in the proposed building), the building shall be considered in compliance with Table 402.1.1 (above). The UA calculation shall be done using a method consistent with the ASHRAE Handbook of Fundamentals and shall include the thermal bridging effects of framing materials. The SHGC requirements shall be met in addition to UA compliance.                                            

                                                                 Table 402.1.3 in 2006 IECC

Simulated Performance Alternative (404)

Compliance based on simulated energy performancerequires that a proposed residence (proposed design) be shown to have an annual energy cost that is less than or equal to the annual energy cost of the standard reference design. Some of the fenestration limitations on this approach are (trade off limitations):

• U-Factor < 0.48 in zones 4 and 5; and < 0.40 in zones 6 to 8 (vertical fenestration)
• U-Factor < 0.75 in zones 4 to 8 (skylights)
• SHGC < 0.50 in zones 1 to 3

Note, the 2006 IECC performance analysis now uses energy cost, not consumption, for comparison (similar to ASHRAE's methods.) This means that electricity use is penalized since it is an expensive fuel.  For fenestration, this means that SHGC may be more heavily credited in the design since a SHGC reduction will result in reduced cooling cost which is electrically driven. This fact may allow the designer to trade off against other components more easily.