Air leakage, how much is too much?
I got a new AC + duct installed last month. After the job was finished, I went up to my attic to check out the duct and found that there was a big leak because I could feel the air blowing out of one of the four main ducts connecting to the central blower and into my hand a few inches away (sorry about the terminology, if you know what I mean please tell me of the correct terminology, thanks).
My contractor fixed that by using a paint brush dipping into some sort of grey compound and spread that around the area where the four main ducts connecting to the central blower. I guess that was to seal the connector air tight. Is that the correct way to fix an air leak from a duct connector, and better than just applying more shiny silver tape on top of the existing one?
As part of my utility rebate they also checked the leakage rate. They told me no house has a zero leakage. Mine is 8% and that's within an acceptable leakage of 15%. Do you think their statements about the air leakage are right?