I would like to add a comment to the Hotline question on residential units that appeared in the Dec. 3, 2001 issue of The News.
It is very important that there are no leaks in the duct of a unit located in the attic. If supply ducts leak, then conditioned air can escape into the attic. This leads to a loss in capacity. Also, warm moist air can be drawn into the supply duct at a leak.