C502.1 General.Additions to an existing building, building system or portion thereof shall conform to the provisions of this code as they relate to new construction without requiring the unaltered portion of the existing building or building system to comply with this code. Additions shall not create an unsafe or hazardous condition or overload existing building systems. An addition shall be deemed to comply with this code if the addition alone complies or if the existing building and addition comply with this code as a single building. This allowance applies to prescriptive compliance in accordance with Section C502.2 or total building performance in accordance with Section C407.

C502.1.1 Additional energy efficiency credits. Additions shall comply with Section C406.1. The addition shall be deemed to comply with this section if the addition alone complies or if the addition area is combined with existing building areas to demonstrate compliance with an additional efficiency credit.

C502.1.2 Renewable energy. Additions shall comply with Section C411. The addition shall be deemed to comply with this section if the addition alone complies or if the addition area is combined with existing building areas to demonstrate compliance with the requirements for on-site renewable energy or solar readiness, as applicable.

C502.2 Prescriptive compliance.Additions shall comply with Sections C502.2.1 through C502.2.6.2.

C502.2.1 Building mechanical systems. New mechanical systems and equipment serving the building heating, cooling or ventilation needs, that are installed as a part of the addition shall comply with Sections C403, C408.2, C501.6, and C506.1.

C502.2.2 Service water heating systems. New service water-heating systems and equipment that are installed as a part of the addition shall comply with Sections C404, C408.3, C501.6, and C506.1.

C502.2.3 Pools and permanent spas. Systems and equipment serving new pools and permanent spas that are installed as a part of the addition shall comply with Sections C404.11, C408.3, C501.6, and C506.1.

C502.2.4 Electrical power and lighting systems and motors. New electrical power and lighting systems and motors that are installed as a part of the addition shall comply with Sections C405, C408.4, C501.6, and C506.1.

C502.2.4.1 Interior lighting power. The total interior lighting power for the addition shall comply with Section C405.4.2 for the addition alone, or the existing building and the addition shall comply as a single building.

C502.2.4.2 Exterior lighting power. The total exterior lighting power for the addition shall comply with Section C405.5.2 for the addition alone, or the existing building and the addition shall comply as a single building.

C502.2.5 Refrigeration systems. New refrigerated spaces and refrigeration systems and equipment that are installed as a part of the addition shall comply with Sections C408.7, C410, C501.6, and C506.1.

C502.2.6 Building envelope. Additions shall comply with Sections C402.1 through C402.5, C502.2.6.1 and C502.2.6.2.

C502.2.6.1 Vertical fenestration. Additions with vertical fenestration shall comply with the following:

1. Where an addition with vertical fenestration area results in a total building vertical fenestration area less than or equal to the maximum allowed by Section C402.4.1, the addition shall comply with Section C402.4.

2. Where an addition with vertical fenestration area results in a total building vertical fenestration area greater than the maximum allowed by Section C402.4.1 (regardless of the ratio prior to the addition), the addition shall comply with one of the following:

2.1. Component performance alternative with target area adjustment per Section C402.1.5 for the addition area of the building only.

2.2. Existing building and addition area are combined to demonstrate compliance with the component performance alternative for the whole building. U-factors applied to existing envelope assemblies in the UA calculation shall comply with Section C501.2.1.

2.3. Total building performance in accordance with Section C407 for the addition area of the building only.

2.4. Total building performance for the whole building.

C502.2.6.2 Skylights.Additions with skylights shall comply with the following:

1. Where an addition with skylight area results in a total building skylight area less than or equal to the maximum allowed by Section C402.4.1, the addition shall comply with Section C402.4.

2. Where an addition with skylight area results in a total building skylight area greater than the maximum allowed by Section C402.4.1 (regardless of the ratio prior to the addition), the addition shall comply with one of the following:

2.1. Component performance alternative with target area adjustment per Section C402.1.5 for the addition area of the building only.

2.2. Existing building and addition area are combined to demonstrate compliance with the component performance alternative for the whole building. U-factors applied to existing envelope assemblies in the UA calculation shall comply with Section C501.2.1.

2.3. Total building performance in accordance with Section C407 for the addition area of the building only.

2.4. Total building performance for the whole building.