How high above the roof does the thing exhaust? Yes, it will add some heat to the attic. If there is adequate ventilation there, it may not be the problem. If the chase where it goes into the attic is not sealed, that may be a bigger, more constant source of heat into the attic. You'd have to read the manual to see if insulation is allowed. Probably wouldn't hurt, if allowed. Not sure it would help. On a run that long, I'd expect more condensation in your drain.