Frequently Asked Questions

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 2015 IECC with Illinois Amendments. Section numbers are from the 2015 IECC. This page will be updated to the 2018 IECC version on July 1, 2019, when the updated Illinois Energy Code becomes effective.

Administration/Legal Questions

Q: When does the updated Illinois Energy Code based on the 2018 IECC become effective? 
A: The City of Chicago has already adopted the updated Energy Code based on the 2018 IECC, and the new Code applies to the projects with permit application started on or after 6/1/2019. For the rest of the state, the Illinois Capital Development Board has set an effective date of 7/1/2019 for the updated Energy Code, based on the 2018 IECC with Illinois Amendments. Please check here for the latest announcements about code adoption.  

Q: If my building is LEED certified, does that guarantee that it is compliant with the Illinois Energy Conservation Code? 
A: No. LEED certification is separate from Energy Code compliance as energy efficiency is a small portion of the LEED rating system. Buildings may be code compliant and not be LEED certified. Conversely, buildings may be LEED certified and not code compliant. LEED does not qualify as an "Above-code Program" under the Illinois Energy Conservation Code. 

Q: A building addition is proposed for an existing building. How can the compliance of the addition be calculated with COMcheck? 
COMcheck determines compliance for additions in the same manner as new construction. When entering an addition, only the new portions of the building need to be shown in the software. COMcheck will perform trade-offs between envelope assemblies when determining compliance. 

Q: When is compliance with the current IECC (2015 or 2018) determined? When the design begins, when the construction documents are complete, or when the building permits have been obtain? 
Typically, it is the date of the application/submission of the permit that dictates which version of the energy code is applicable. However, we recommend confirming with the local code official since it is ultimately the Authority Having Jurisdiction who has the final say.  

Commercial Questions

Q: Can a permit applicant mix and match provisions of IECC Section 4 and ASHRAE Standard 90.1 on a single permit application for compliance assessment?
A: [C401.2] No, designers are not permitted to "cherry-pick" a customized path to compliance by combining provisions of both ASHRAE Standard 90.1 and IECC. Either code must be used in its entirety with applicable Illinois Amendments. 

Q: How might the Energy Code apply to a proposed building without heating and cooling?
A: [C402.1.1]
This building does not "contain conditioned space," it may qualify as a "low-energy building," making it exempt from the building thermal envelope provisions. 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 C503.2). 

Q: Does the 2015 IECC require a loading dock to be insulated? 
A: [C402] If the loading dock qualifies as a "low-energy building" (see section C402.1.1), then the loading dock would be exempt from needing to be insulated, including the loading dock weatherseal provisions (C402.5.6). The loading dock would be required to be thermally separated from the remainder of the building, unless the whole building qualifies as a "low-energy building." If the loading dock does not qualify as a "low-energy building," it is required to follow the building envelope requirements (C402).

Q: Do "net zero" buildings (geothermal wells, natural roof area, roof-mounted photovoltaic panels) need to comply with any of the requirements of the IECC? 
A: [C402.1.1]  The building is required to be in compliance with the electrical and lighting provisions of Section C405. If the building qualifies as a "low-energy building," it is not required to comply with the building thermal envelope provisions of Section C402.1.1.  

Q: How might the Illinois Energy Conservation Code (2015 IECC) apply to the roof insulation of a parking garage? 
A: [C402.1.1] The parking garage may qualify as a "low-energy building" (or portion thereof). If it does, then the parking garage would be exempt from the building thermal envelope provisions. If the peak design rate of energy usage is above this level required to qualify as a "low-energy building," then the parking garage must comply with all the requirements of Section C402. 

Q:  In "through-fastened" or "screw-down" metal roofing where batten insulation is draped over purlins and then compressed as metal purlins are attached, how do you meet the required R-values? 
A: [Table C402.1.3] The Illinois Energy Conservation Code requires all metal building roof systems to be provided with "thermal spacer blocks" to limit conduction and a Liner System (LS) to limit air leakage. 

Q: Could you explain the "tapered insulation" provisions? 
A: [C402.2.2] Tapered insulation of roofs cannot vary more than 1-inch from the required minimum. For instance, if 5 inches of insulation are required to meet the specified R-value and tapered insulation is going to be used, the minimum tapered insulation of the roof would be 4 inches. The area-weighted average insulation U-factor for the entire roof field would need to achieve the minimum U-factor equivalent to the R-value specified in Table C402.1.3.  

Q: To be compliant with the economizer fault detection and diagnostics (FDD) requirements, can we use a thermostat that only indicates there has been an economizer fault of some kind?
A: [C403.2.4.7, item 6] 
Yes. The fault may be annunciated locally on zone thermostats.

Q: Do the multiple compressor staging requirements only apply to VAV controlled units? 
A: [C403.4.1.1] 
They only apply to hydronic and multiple-zone HVAC units. However, there are multiple staging requirements in C403.3.1 which apply to single zone HVAC units. 

Q: Is it acceptable for a stairwell with no manual switches to have 100% of the lighting on occupancy sensors that take a few seconds to respond? 
A: [C405.2] The Illinois Energy Conservation Code exempts interior exit stairways from requiring lighting controls. There is nothing in the Code that prohibits occupancy sensors in stairwells. However, turning off 100% of stairwell lighting may pose a safety risk. 

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. 

Q: Are manual daylighting controls permitted by the Code?
 [C405.2.3] No. Daylight-responsive controls are required to be automatic, not manual. 

Q: What are the Energy Code requirements for commercial lighting alterations? 
A: [C503.6]
Alterations to any building or structure should comply with the requirements of the Code for new construction with some exceptions. If less than 10% of the luminaries are replaced and the lighting alterations do not increase the interior lighting power, the lighting alterations are exempt from meeting the requirements of the Code.

Residential Questions

Q: Does a 3-season room have to meet the requirements of the Energy Code? Does a fireplace count as a heater for determining if a 3-season room is a low-energy building? 
A: [R402.1] A 3-season room must comply with the Illinois Energy Conservation Code. However, if a 3-season room qualifies as a low-energy building or a portion of a low-energy building, it is exempt from meeting the envelope requirements of the Code. Fireplaces do count as heaters for determining low-energy qualifications. 

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: Could you explain the Code requirements for basement wall insulation? 
A: [R402.1.2] Per Table R402.1.2 from the IL Amendments, basement walls are to be insulated with R-10 continuous insulation on the interior or exterior of the home or R-19 cavity insulation at the interior of the basement wall. Section R402.2.9 of the IL Amendments states that this insulation from the top of the basement wall should extend down to 10 feet below grade or to within 6 inches of the basement floor, whichever is less. Exception: Insulation can extend 4 feet below grade when the basement R-value is at least R-15 continuous or R-19 cavity insulation.  

Q: What is the minimum continuous insulation level required for low-sloped (flat) roofs without attic spaces? 
A: [R402.2.2] In addition to meeting the requirements of Section R402.1, please refer to Section R402.2.2 for roofs/ceilings without attic spaces. Minimum R-49 is the requirement for roofs/ceilings per Table R402.1.2. If the design of the roof/ceiling does not allow sufficient space for insulation, minimum R-30 is allowed to 500 sf or 20% of the total insulated ceiling area, whichever is less. This reduction cannot apply to the U-factor alternative and total UA alternative in R402.1.5.  

Q: Could you please clarify the code regarding the reduction of R-5 continuous insulating sheathing where walls are partially covered with structural sheathing? 
A: [R402.2.7] In addition to meeting the requirements of Section R402.1, please refer to Section R402.2.7 for walls with partial structural sheathing. Minimum R-20 or R-13+5 is the requirement for wood framed walls per Table R402.1.2. If the structural sheathing covers 40% or less of the gross area of all exterior walls, there is an allowance for R-value reduction of no more than R-3 (R-5 down to R-2) for the portions with structural sheathing. Otherwise, R-5 continuous insulating sheathing must be applied over the entire building thermal envelope. 

Q: What are the air sealing/air barrier requirements for rim joists? 
A: [Table R402.4.1] 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 of the building envelope also 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 5 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: Does the blower door testing have to be done by a third party?
A: [R402.4.1.2] Yes. Where required by the code official, the blower door testing must be conducted by an approved third party or an approved inspection agency. 

Q: What are the requirements with regard to fireplace air leakage control? 
A: [R402.4.2] The code requires wood fireplaces to have either tight-fitting flue dampers or doors, and outdoor combustion air.  

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 a wood-framed wall of an existing residential building is being re-insulated, what is the minimum required R-value based on climate zone? This is not for whole wall assembly, but rather interior alterations which require removing and replacing wall cavity insulation and applying new interior drywall finish.
A: [R503.1.1] Envelope assemblies that are part of the alteration should comply with Section R402 with some exceptions provided the energy use of the building is not increased. One of the exceptions in R503.1.1 is for existing ceiling, wall or floor cavities exposed during construction. Per R503.1.1 exception 2, existing cavities can be filled with insulation to meet the envelope requirements. For example, Table R402.1.2 calls for R-20 cavity insulation, but filling the cavity may only provide R-15 insulation. Filling the cavity is important to minimize convection within the wall cavity.