I recently did a duct leakage test using the CFM25 method and was informed that the ideal leakage rate should be less than or equal to 4 CFM25 per 100 square feet of conditioned space. From my research, I calculated that my leakage limit should be 174 CFM total for my entire house. Since I have two zones, zone 1 was tested at 40 CFM and zone 2 at 98 CFM, bringing my total to 138 CFM. This seems quite high to me, and I think it gives my system a rating of around 3.17. Since my home is new and was supposed to be energy-efficient, I'm a bit concerned about these results and would really appreciate some insights on whether this is bad or not.
1 Answer
It's a bit hard to say definitively without more context, but generally, a total of 138 CFM seems higher than the target. As a rule of thumb, the ducts should ideally be in your living spaces like inside the walls or ceilings, rather than in unconditioned areas like attics or crawl spaces. If they’re properly located, fixing leaks could help improve your efficiency!
But aren't most ducts typically placed in attics or crawl spaces in standard homes? How does that affect the efficiency?