How much air leakage in CFM can my change-out or alteration job have?
In short answer, there are 4 ways to obtain passing results- 3 ways that deal with actual calculated air flow and leakage in CFM. Those 3 ways are A) 15% of calculated airflow can leak using the 400 CFM per ton formula as explained in the the following question. B) 60% reduction achieved in comparison to the initial leakage test performed before the change-out. C) Measure the amount of leakage to the outside, and make sure it’s less than 10%. Measuring leakage to the outside requires the use of a blower door, and ducts supplies still have to be taped off. D) Finally, if 1 of the above 3 passing methods can’t be achieved, passing results can be obtained so long as the contractor seals all accessible visual leaks and that has been visually verified with smoke by a HERS rater.
