Finally, I have two solid quotes for air sealing. I have one new concern, however. My finished attic gets really hot in summer, and the A/C dedicated to this attic rarely is able to cool the space below 82 degrees. From what I have read, besides implementing some kind of reflective roofing material, the only way to keep an attic cool is plenty of airflow. So, if we air seal the attic and add insulation (which I have read holds and radiates heat in summer ?), is this air sealing initiative going to make my attic unlivable in the summer?
Hey there R-
First thing to do is stop thinking about your top floor as an attic of any type. Yes, it used to be an attic, but now it's supposed to be inside the enclosure, so let's call it what it is- your valuable living space.
Not only will airsealing NOT going to make your top floor (finished attic) hotter in summer, it is in fact the ONLY THING that will make it cooler up there. What's happening is called reverse stack effect: your air conditioners are creating cooler, drier, DENSER air, which sinks to the bottom of the house. All the air conditioning wants to be in the bottom of the house at the same time, so it creates a higher pressure down there, and there's a low pressure at the top of the house.
The cool, heavy air escapes through gaps and cracks in the bottom of the house, and the house now needs air, so it breathes in at the most depressurized (and also hottest) place- at the very top. So all the air that's in your top floor rooms is coming from the attic spaces and the roof cavity.
Lastly, it's a total myth that attic ventilation will keep an attic cool- #1, attic ventilation is actually for venting MOISTURE, not heat; and #2, you don't actually care how hot it gets in your attic, since it's not part of your house. The roofing manufacturers used to void their warranties if the attic got too hot, but they don't do that anymore. You're free!
For a more detailed look at attic airsealing, watch this: