Knox County, TN HVAC permit requirements

2018 IRC with Knox County amendments (Knox County Code Sec. 10-56/10-57; Ord. O-18-10-101, Nov 19, 2018; amended Ord. O-23-4-101, May 22, 2023). Energy-related IRC amendments: the Climate Zone 4 row of Table N1102.1.2 is changed to ceiling R-38 (not 49) and wood-frame wall R-13 (not '20 or 13+5'); N1102.4.1.2 testing is '(optional)' 'Where required by the building official'; N1103.1.1 programmable thermostat and N1103.2.2 duct sealing apply 'Where required by the building official'; N1103.6 mechanical ventilation is made 'Optional'.

2018 IECC with Knox County amendments (Sec. 10-301/10-302). R101.5 is amended so compliance may be shown under the IECC 'or Chapter 11, Energy Efficiency, of the International Residential Code' (2018 IRC as amended above).

2018 IRC M1401.3 is kept. The Sec. 10-57 amendments contain no M14xx sections, and 2018 IECC R403.7 is not amended in Sec. 10-302. M1401.3 requires Manual S sizing based on Manual J loads 'or other approved' methodologies.

2018 IRC M1601.1 is kept; the Sec. 10-57 amendments contain no M16xx sections (Manual D, the manufacturer's instructions, or other approved methods). The county duct handout (Rev. 022019) restates N1103.3.1 duct insulation of R-8 in attics and R-6 elsewhere (3 in. and larger).

Per the county handout: 'Inspectors will verify energy conservation code requirements based upon 2018 IRC regulations as amended by Knox County. The owner/contractor will sign the certificate verifying the type of insulation and the equivalent R-values'. The handout lists prescriptive values (attic R-38, wood wall R-13, floor R-19, window U-0.32, HVAC duct 'R-8 in Attic(All other R-6)'). Envelope is 'tested or inspected'. IRC Chapter 11 or the IECC may be used (R101.5 amendment). REScheck, performance and ERI are not mentioned.

No county mechanical permit checklist requiring Manual J/S/D or heat loss/gain was found. The county runs an online 'Permit Application' page for unincorporated Knox County.

www.knoxcounty.org/codes/online_permits.php