A debate has continued in the industry about whether boiler jacket loss should be factored into the calculation of boiler efficiency. Most of the old boiler rooms were very toasty places. If the old pipe insulation was removed, the boiler room was downright hot. While some believe the heat lost through the boiler jacket into the boiler room is wasted, others feel it is useful heat. Jacket loss is the transfer of heat from the boiler through the jacket and into the boiler room.
I would rather not get in the middle of that controversy but I do know one thing: Jacket loss trumps polyester pants every time.