The 2021 International Energy Conservation Code (IECC) became effective on November 1, 2024. The following are some specific code requirements of the 2021 IECC related to residential construction following the prescriptive compliance option from §401.2.1. Please refer to the code to reference all applicable requirements including additional requirements for commercial construction.
- Insulation: The State of Maryland has provided an alternative insulation
Document
Table R402.1.3.1
(301.6 KB)
for use when combined with §R408.3. Otherwise,
Document
Table R402.1.3.pdf
(444.75 KB)
applies. All of Garrett County is considered Climate Zone 5.
- Sunrooms and Heated Garages: If thermally isolated from the home, sunrooms and heated garage must have a minimum of R-24 in ceilings and R-13 in walls. The wall separating sunrooms and heated garages from conditioned space must comply with Table R402.1.3.
- Under-slab insulation: R-5 continuous required under the full slab area of a heated slab in addition to the required slab edge insulation R-value from table R402.1.3.
- Duct Testing: Air leakage testing is now required on all duct work. A copy of the test results must be submitted to the Permits Office from the third-party testing agent.
- Ducts Outside Thermal Envelope: - Leakage Rate ≤ 4.0CFM/100SF of floor space
- Ducts Within Thermal Envelope: - Leakage Rate ≤ 8.0CFM/100SF of floor space
- Mechanical Ventilation: Testing of Mechanical Ventilation systems is now required to ensure compliance with section M1505 of the IRC or IMC. A copy of the test results must be submitted to the Permits Office from the third-party testing agent.
- Blower Door Testing: Air Leakage rate of ≤ 3.0ACH50 is required. For attached single family, multi-family dwellings, and for dwellings ≤ 1,500 SF, a leakage rate of 0.30 CFM per SF of enclosure area is allowable. A copy of the test results must be submitted to the Permits Office from the third-party testing agent.
- Log Homes: Must comply with the standards of the 2021 IECC or ICC 400. Documentation of compliance with ICC 400 is required, or the 2021 IECC standards will apply.
- Manual J & Manual S: Manuals J & S are protocols developed by the Air Conditioning Contractors of America (ACCA) to help properly size HVAC equipment. Manual J consists of load calculations that accurately determine a home’s heating and cooling needs. Manual S is then used to select the properly sized heating and cooling equipment based on Manual J load calculations. In new homes with a forced air heating system, a copy of the Manual S & J calculations must be submitted to the Permits office and must be available for review by the building inspector during the final inspection. Alternatively, the HVAC equipment may be verified by an approved third-party testing agent.
- Additional Energy Features: If using the prescriptive compliance path of §R402.1.3.1, an additional energy efficiency package must be selected from Document Table 408.3 (620.05 KB) . A minimum efficiency increase of 6% is required for Climate Zone 5.
