Note: The responses to the questions below are based on the Illinois Energy Conservation Code. SEDAC is the Energy Code Training Provider for Illinois EPA and is not the code official nor the authority having jurisdiction. As such, the opinions expressed below are advisory and not a legal interpretation.

"The Code" or "the Energy Code" refers to the current Illinois Energy Conservation Code, which is based on the 2018 IECC with Illinois Amendments. Section numbers are from the 2018 IECC.

Administration/Legal Questions

Q: When did the updated Illinois Energy Code based on the 2018 IECC become effective? 
A: The Illinois Energy Code based on the 2018 IECC with Illinois Amendments became effective 7/1/2019. For the City of Chicago, the updated Energy Code based on the 2018 IECC became effective on 6/1/2019.

Q: How do I know which version of the Illinois Energy Code my project is required to follow?
A: 
The code version is generally determined by the date of the permit application. For permits in Illinois, all permits submitted after 7/1/2019 must comply with the 2018 IECC version. For permits in Chicago, all permits submitted after 6/1/2019 must comply with the 2018 IECC version. Ultimately, the Authority Having Jurisdiction has the final say on which version to use, so check with your local Authority Having Jurisdiction to verify the version for your project.

Q: Can I use both ASHRAE 90.1 and IECC for Energy Code compliance?
A: 
Projects must choose one compliance path for minimum Energy Code Compliance. Designers are not permitted to "cherry-pick" a customized path to compliance by combining provisions of both ASHRAE Standard 90.1 and IECC 2018. Either code must be used in its entirety with applicable Illinois Amendments. Projects may choose to go beyond minimum code compliance, but minimum code compliance must be demonstrated using a single compliance path.

Q: I am working on an elementary school. Who is the Authority Having Jurisdiction for code enforcement?
A: 
According to Title 23 of the Illinois Administrative Code Part 180 Health/Life Safety Code for Public Schools, the Authority Having Jurisdiction is the Regional Superintendent.

Q: I have a mixed-use building. How do I determine which provisions (residential or commercial) apply?  
A: [C101.4.1, R101.4.1] For mixed residential and commercial buildings 3 stories or less (4 or less in Chicago), each portion must separately consider and meet the applicable commercial or residential provisions. Mixed residential and commercial buildings larger than three stories (four in Chicago) are considered commercial buildings, and residential portions of these larger buildings do not need to meet separate residential provisions.

Commercial Questions

Q: How might the Energy Code apply to a proposed building without heating and cooling?
A: [600.310]
 If the building does not "contain conditioned space," it does not need to comply with the Illinois Energy Conservation Code. Be aware that if the building is changed in the future and no longer qualifies as a low-energy building, it may require substantial work to bring the envelope into compliance (See Title 71 Section 600.310 of the IL Administrative Code).

Q: When is an air-side economizer required?
A: [C403.5] 
The prescriptive requirements of the 2018 IECC require economizers to be used in buildings based on cooling capacity. The capacity limits are modified based on climate zone and occupancy class. For fan cooling units, the occupancy of the building (residential or non-residential) and the system size are the determining factors. See Section C403.5 for thresholds of fan system cooling capacity. Keep in mind this should be Total Net Capacity and that you are checking against the larger of the two values. First, check if the Total Net Capacity in Btu/h of your building is larger than the value given for your occupancy (1,500,000 Btu/h for Group R and 300,000 Btu/h for all other). If total building capacity is below the value given, an economizer is not required.

If you are using the performance path to compliance rather than the prescriptive path, installing an economizer is not required as long as energy performance requirements are met. Learn more about air-side economizers and code compliance here.

Q: If shutting off lights will present a life safety hazard for occupants, are you required to have occupancy sensors in egress stairways and corridors? 
A: [C405.2] No. C405.2 Exception 2 states that lighting controls are not required for interior exit stairways, interior exit ramps, and exit passageways. Further C405.2.1.1 states, "Full automatic-on controls shall be provided to control lighting [in areas] where manual-on operation would endanger the safety or security of the room or building occupants."

Q: Are you permitted to install occupancy sensors in a stairway or public corridor? 
A: Maybe. This question is not addressed in the 2018 IECC; instead, please check the safety requirements of other local and national codes that have jurisdiction over the project. Some relevant safety codes include the Chicago Building Code, the 2018 IBC, and the Life Safety Code (NFPA 101). We reviewed these codes and found that generally you can have energy saving motion sensors for lighting in designated egress zones, as long as they meet certain safety requirements. For instance, you are not required to illuminate paths of egress in normally unoccupied areas of the building or service support areas. Therefore, support areas may be great places to take advantage of motion sensitive lights.

Q: Is daylight harvesting and daylight zone control required by the Energy Code? 
A: [C405.2.3] Yes, if there are more than 150 watts of general lighting in the sidelit or toplit zone. There are some exceptions provided for certain applications. For instance, areas are exempt from meeting the daylight zone control requirements if the area weighted lighting power density is less than 40% of normal LPD for the space type (Exemption #4, see also C406.3).

Q: I am renovating a commercial building. Do I need to bring my building's envelope up to full compliance with the 2018 IECC? 
A: [C502, C503 & C505.1]. If a space changes occupancy or use, the space must meet the 2018 IECC envelope requirements. For example, if an unconditioned storage area is converted into an office space or a warehouse is converted into residential lofts, these spaces must be insulated to the current energy code. If part of a building is altered or new construction is added to the building, the altered or added parts of the building must comply with envelope requirements, but the code requirements do not apply to the unaltered parts of the building.

Q: When I'm doing roof work, when do I need to add insulation?
A: [C503.3.1, C504]. There are several kinds of roof work. Some of them trigger compliance with the IECC envelope requirements, some do not.

  • Roof replacement is defined as the process of "removing the existing roof covering, repairing any damaged substrate and installing a new roof covering." During roof replacements, section C503.3.1 requires the roof deck to be brought into compliance with the IECC thermal envelope requirements if "the existing roof assembly is part of the building thermal envelope and contains insulation entirely above the roof deck." Roof replacement presents a unique opportunity to add insulation. We strongly recommend that you meet or exceed the minimum insulation requirements, if feasible.
  • Roof membrane peel and replacement is defined as removing the existing membrane and installing a new membrane, but not replacing any roof decking or insulation. This type of roof work is currently exempt from the envelope requirements (see Illinois Amendments).
  • Roof recover is defined as "the process of installing an additional roof covering over a prepared existing roof covering without removing the existing roof covering." Section C503.1 indicates that roof recovers are not required to meet the IECC insulation and envelope requirements.
  • Roof repairs are defined as "reconstruction or renewal of any part of an existing roof for the purposes of its maintenance." These are also exempt from meeting the IECC insulation and envelope requirements (C504).

Q: For a low slope roof replacement, what should be done if there is not enough room to provide the full R-30 insulation and install flashings properly?
A: [C503.1, C402.1] 
Complying with requirements for alterations does not "require unaltered portions of the existing building to comply with the code" or "create unsafe or hazardous conditions or overload existing building systems." This suggests that the amount of insulation should be brought as close to the level required by the Code, while accounting for restrictions of existing conditions (parapet walls, equipment curbs, fenestration, etc.) and manufacturer's flashing installation directions. The level of insulation after the roof replacement may not be less than what it was before the roof replacement.
In addition, there is an Illinois Amendment which covers "roof membrane peel and replacement." When the membrane is removed and replaced with no insulation work or roof deck work done, this would not require the roof insulation to be increased. However, not inspecting the roof deck may not follow the recommended practices of the National Roofing Contractors Association. It is recommended that the feasible additional insulation be planned in the project rather than rebidding if insulation or roof deck repairs are needed.

Residential Questions

Q: What is a "low-energy" building per the Energy Code?
A: [R402.1]. 
A low-energy building is a building that has a peak design rate of energy usage less than 3.4 Btu/h • ft2 or 1.0 W/sf of floor area for space-conditioning purpose. A building that does not contain conditioned space is a low-energy building.

Q: What are the air sealing/air barrier requirements for rim joists?
A: [Table R402.4.1.1]. 
Rim joists should include the air barrier and insulation, and the air barrier should be continuous per Table R402.4.1.1. Air-permeable insulation, such as fiberglass, should not be used as a sealing material. Components fo the building envelope should be installed according to the manufacturer's instruction.

Q: What is the maximum air leakage rate allowed per Code?
A: [R402.4.1.2] 
Per Illinois Amendments, the Code requires buildings to be tested and verified as having an air leakage rate not exceeding 4 air changes per hour (ACH). The building should be provided with a whole-house mechanical ventilation system as designed in accordance with Section R403.6. Air leakage testing should be conducted in accordance with ASTM E779 or ASTM E1827 and reported at a pressure of 50 pascals.

Q: Is diagnostic testing required for assessing compliance with the Energy Code?
A: [R402.4.1.2] 
Yes. The air leakage testing called for in Section R402.4.1.2 will require diagnostic testing equipment such as a blower door to be used for compliance verification. This is a mandatory provision of the code and therefore is required regardless of the compliance path chosen.

Q: Are permits required for window replacements? 
A: Permit requirements vary by jurisdiction. Check with your local jurisdiction to determine their permit requirements.

Q: If I open a wall, do I need to add the required amount of insulation if there isn't enough space?
A: [R503.1.1] Building envelope assemblies that are part of the alteration are required to follow certain envelope requirements, including insulation requirements, but there are a number of exceptions. Exception 2 would likely apply to this situation: "Existing ceiling wall or floor cavities exposed during construction" do not need to comply with these requirements "provided that the energy use of the building is not increased" and "provided that these cavities are filled with insulation." Thus, the wall would not need to be expanded to add R-20 insulation, but it would require insulation to fill the cavity. R-13 or R-15 insulation would likely be sufficient for a 2X4 wall.

Note that for masonry walls, an air gap should be left between the masonry and the wall/insulation because masonry absorbs water and needs to be able to dry or it will degrade. Leaving no air gap would violate the requirement that "alterations shall not create an unsafe or hazardous condition or overload existing building systems" (R503.1).

Q: I am renovating a house but not changing space conditioning requirements; what envelope requirements must I meet?
A: [R503.1.1]. If your renovation is not changing occupancy or energy use of the space, you are often not required to bring the existing portions of the building into compliance with the 2018 IECC envelope requirements in section R402. When a floor, wall or ceiling cavity is opening in the process of a renovation that portion of the envelope is not required to be brought up to the new construction level as long as the cavity is filled with insulation, and the renovation is not changing space conditioning requirements. If the cavity is not filled with insulation, the 2018 IECC requires that you add it.

Q: For a low slope roof replacement, what should be done if there is not enough room to provide the full R-30 insulation and install flashings properly?
A: [R503.1] 
Code compliance for alterations does not "require unaltered portions of the existing building to comply with the code" or "create unsafe or hazardous conditions or overload existing building systems." This suggests that the amount of insulation should be brought as close to the level required by the Code, while accounting for restrictions of existing conditions (parapet walls, equipment curbs, fenestration, etc.) and manufacturer's flashing installation directions. The level of insulation after the roof replacement may not be less than what it was before the roof replacement.

In addition, there is an Illinois Amendment which covers "roof membrane peel and replacement." When the membrane is removed and replaced with no insulation work or roof deck work done, this would not require the roof insulation to be increased. However, not inspecting the roof deck may not follow the recommended practices of the National Roofing Contractors Association. It is recommended that the feasible additional insulation be planned in the project rather than rebidding if insulation or roof deck repairs are needed.