#2228 Standard Design for Altered Fenestration

[Felicia Lee]

We have a commercial office building retrofit project where we will replace the existing windows. My understanding is the windows will be “Altered” components, and Table 141.0 D have two baseline options for altered windows, with and without third party verification of existing condition. My question is in CBECC-COM, when we use performance method to show compliance, how to make CBECC-COM use existing U-factor and RSHGC level as the baseline. The baseline model in CBECC-com is by default table 141.0-A, which is the case without third-party verification.

[John Arent]

Response to user, 4/17:

For the performance compliance approach using CBECC-Com, the third-party verification approach specified in Table 141.0-D of the Standards is not applicable. If fenestration is altered, the standard design (baseline) is determined from Table 141.0-A of the Standards. So the fenestration baseline is not as stringent as the baseline for new construction, but it may be more stringent than the existing fenestration.

If fenestration is existing an unaltered, the standard design matches the existing condition.

Please let me know if you have any further questions.

Best regards, John