I am getting ready to replace the exhaust fan in my main bathroom with a fan/heater combination. When I found the fan the first thing that caught my eye was that the builder did not exhaust the fan to the outside. The fan just exhausted right into the blown insulation. Now I am getting ready to put in the fan/heater and I do want to exhaust it somewhere other than into the insulation and was going to put a 4 inch galvanized line with a 90 degree elbow and just exhaust it into the attic, I can see no other way of doing it. I would put the 90 on a 45 degree angle so as not to vent the moist air straight up where it may possibly trap a bit of moisture, especially in the winter then the galvanized is cold. Any ideas?