I had to crawl under my house a few days ago to run some TV cable, and I noticed that the main line coming from my a/c unit into the house doesn't have any insulation around it. The heater was on so the line felt warm when I touched it. Am I losing some heat by not having insulation on this line?

I don't know what the line is called, but it's looks like copper and has the refrigerant running through it.