Whether you are creating conditioned space from and existing garage, closing in and conditioning a porch, or adding on new construction square footage, the requirements for meeting Florida energy compliance for an addition can vary from meeting the same for new construction. Here’s a few key things to keep in mind before you submit the job for permit:
Supplying A/C for the addition using the exiting home A/C unit: If you intent to use the existing home A/C unit to supplement A/C to the addition, most plan reviewers are going to want a Manual J (load calc) that includes the area of the existing house plus the addition to ensure the existing A/C unit is going to be large enough for both. This can be a royal pain for the contractor and the Energy Rater because running the Manual J in this case requires detailed plans for the whole house (not just the addition). All too often with these types of projects, whole house plans are not readily available, forcing a sketch of the existing portions of the home to be created in order to satisfy the needs of the energy model. This eats up time and resources that the contractor often times did not anticipate.
Envelope Leakage testing for additions: If the prescriptive method of the Energy Code R502 is used to meet energy compliance (most common method for small additions), then there is an exception stated in the code that “air leakage testing is not required for additions, alterations, renovations or repairs of the building thermal envelope of existing buildings in which the new construction is less than 85 percent of the building thermal envelope”. Most of the time with small additions this is the case, and the blower door test can be waived. (However, if the Performance Compliance, section R405 method is used, envelope leakage testing will be required.)
Duct Leakage testing for additions: Again, if the prescriptive compliance method is used, ducts need to be tested unless the ducts and air handler(s) are entirely within the building thermal envelope. An exception in Section R502.1.1.2 also waives duct testing requirement for ducts extended from an existing heating and cooling system to an addition that are less than 40 linear feet.
Keep these few key things in mind next time you plan out the cost it takes for a small addition to meeting energy compliance.