The previous owner of our house spent 2 hours telling us useful information about the house, and mentioned that if we hear something in a specific wall, it may be refrigerant lines to the upstairs heat pump. I saw that large holes were drilled to gain access for the refrigerant lines in an interior wall and contained the copper lines to the attic heat pump. Much later, when I was doing some sealing and insulating in the basement, I found the original hole and original copper refrigerant lines that went up within an exterior wall to the attic heat pump. They were still intact from flush with the basement ceiling to the attic rafters, where they were cut. I pulled them out and sold the copper at a recycling center.
Why would someone cut the lines and send up 20' of new copper tubing to do this? All that I can guess is someone suggested that having the lines in an exterior wall means there is more heat gained or lost to the outside. Is that enough to justify the expense of this replacement? Is it now standard to keep such lines away from exterior walls?