Central air unit in attic
I'd want a lot more info.
Did he give you a price? (Putting vents throughout a house that has none has got to be expensive.)
What type of heat do you have now?
I'd get a second and a third professional opinion.
I didn't move into the place until after the systems were installed, so I can't really compare "before" and "after" attic temperatures. I can say that the attic didn't get extremely hot in the summer with the units running in the attic. The exhaust fan didn't kick on too often that I can recall. The attic was a little warmer in the winter, which I attributed to the heating systems and the insulation. Then again, the walls of this house had NO insulation in them and the interior surfaces were plaster, so I felt the cold wind!
The landlord told me it cost about $10,000 for both systems to be installed plus the blown-in insulation (all done by 1 company). The landlord did this to help the house sell...I moved in during July 1999 and they sold the house in September 2000. I hope this information is of use to you. Jim D/Heathsville, VA