Thank You in Advance for your help. I just moved into a new condo. We have 2 zones. 1 upstairs 1 down. There is a air intake, I think it is called, when air conditioning is on it pulls air into it. It is a very large hidden space behind a 4 foot tall 3 foot wide grill. There is a open void that can fit 3 of me in there and I way 230lbs, big area. I can see sunlight coming in through duct from this to the rooftop ac. My problem is that when this ac is not on there is a large amount of heat coming in through it into the house. Is this normal? Is there a way to stop this from happening?