Making sure homes are energy efficient, verifying a good pressure thermal boundary, proper air flow for a healthy home as well as CAZ saftey testing. 4.

They can also turn on the fan in bathroom and over the stove to increase air flow without opening a window.

I had this problem and once I opened up the vent to allow full air flow the condensation went away.

I came home to an email that said " if my air conditioner is not fixed by 6 PM I am calling the police on you for endangering our lives" I emailed back and asked if he had recieved the fan i had our handyman dropped off, he said yes.. then I asked if he had opened the windows for air flow.. he said he wouldnt open the windows due to safety issues..

Im no expert, but typically (I'm told) running but not heating is just an air flow issue.

run a load calculation on the house to determine size of unitbut you also need to look at the air flow going to the 3rd floor and where it's coming from If it's coming from basement 3 floors is a long way to push air going upNot going to do any good to increase size of unit and duct work won't handle itThe more bends in duct the more restrictions If you get enough air to cool it there will be way to much to heat itFlat roof doesn't give you many optionsHate to say it but window unit might be an option

Look at the insulation in the attic, look at your soffits to make sure you're getting enough airflow through the roof.

I would drop it to about 18 inches, that way you can get better air flow for flame combustion and you do not restrict the heat it gives off.  

But with the minisplit AC we needed the airflow.  

@Isiah Ferguson it easily has the capacity, you will just need to keep the doors open to get the airflow to each room