IECC 2015 - State Building Code (Illinois)

Last updated: 15 February 2019
Development Authority: International Code Commission

Implementation Authority: Local authorities

Verification Authority: Code official

Prescriptive Compliance path
Occupiable space, excluding crawl spaces and garages

Energy Requirements:
U-Values (Btu/h.ft2) Floor Roof Walls Windows
Climate zone 1 0.064 0.035 0.197 1.2
Climate zone 2 0.064 0.035 0.165 0.65
Climate zone 3A and 3B 0.047 0.035 0.141 0.5
Climate zone 4A and 4B 0.047 0.03 0.141 0.35
Climate zone 4C 0.033 0.03 0.082 0.35
Climate zone 5 0.033 0.03 0.082 0.35
Climate zone 6 0.033 0.026 0.06 0.35
Climate zone 7 0.033 0.026 0.057 0.35
Climate zone 8 0.028 0.026 0.057 0.35

The total glazed area may not exceed 18% of the conditioned floor area using the prescriptive method SHGC (for all fenestration including skylights) is 0.30 W/m2.k for climate zones 1-3. No SHGC requirement for other zones
Skylights individually are 0.75 W/m2.k zones 1-2, 0.65 W/m2.k zone 3 and 0.60 W/m2.k zones 4-8
Air Leakage
7 ACH at 50Pa. The thermal envelope must be verified even when using the perscriptive method
Space Heating System
At least one thermostat shall be provided for each separate heating and cooling system. Specific requirements exist for ducts, piping, ventilation, pool systems and snow melt systems Requirements are relative to equipment size and building type.
Water Heating System
All circulating service hot water piping shall be insulated to at least R-2 and have automatic or accessible manual switches to turn off the pump when the system is not in use
A minimum 50% of lamps in permanently installed lighting fixtures shall be high-efficacy lamps.
Renewable Energy
Pools deriving >60% heating energy from site-recovered or solar energy are exempt from pool specific energy saving measures
Compliance Softwares:
End-uses considered:
Space cooling, Space heating, Water heating, Ventilation
Performance Compliance path
Not a requirement / performance based elements are based on a reference model and are relative to energy costs

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