Details of the New Illinois Energy Code

Codewatcher Illinois energy code

The Illinois energy code, based largely on the 2018 IECC, is slightly weaker than the model code.

In mid-September, the Capital Development Board approved the proposed energy code, with
minimal exceptions. The state energy code, based largely on the 2018 IECC, is slightly weaker than the model code. Here are the highlights:

  • The ACH50 number was lowered from 5 to 4, though it is still above the model code’s number of 3.
  • The state code calls for lighting with an efficacy of not less than 65 lumens per watt or light fixtures of not less than 55 lumens per watt.
  • The fenestration U-factors were modified ever so slightly, from 0.35 in climate zones 3 and 4 to .032 and, in climate zones 5 through 8, from 0.32 to 0.30. The glazed SHGC in climate zone 4 (except marine) was changed from not required to 0.40.
  • There is an exception for skylights. If the skylight’s SHGC doesn’t exceed 0.30, it is permitted to be excluded from the requirements of climate zones 1-3.
  • RESNET/ICC 380 is now an acceptable test method in the state.
  • An exception to the ACH50 testing section was added for multifamily buildings. The leakage rate cannot exceed 0.25 cfm per s.f. An approved third party can conduct the testing, if the code official allows. Also, a sampling protocol was entered into the code, whereby the first 7 units must be tested without failure. If that occurs, remaining units can be sampled at a rate of 1 in 7.
  • The state continued to omit the model code section on rooms for fuel-burning appliances.
  • Duct testing is mandatory at rough-in and postconstruction. Total leakage shall be measured with a pressure differential of 0.1 inch w.g. (25 Pa) across the entire system. The two exceptions to the duct leakage testing are: 1) where the ducts and air handlers are located entirely within the building thermal envelope, and 2) ducts serving heat or energy recovery ventilators that are not integrated with ducts serving heating or cooling systems.

The new code will go out for final public comment soon, and it is anticipated that the new energy code will take effect on March 1, 2019.