Heck in my own house one bathroom door is just slightly off balance that if the fart fan is running and the furnace kicks on, the door will move all by itself due to the change in air flow.

Airflow requirements are much less for heat than cooling.

If the store fronts are/were restaurants, check to see if they still have the hoods and air flow evac systems and fire suppressant systems.

Typically this problem occurs when you have the thermostat on the main floor, where most of the air flow is needed.

Article is here: http://money.cnn.com/2007/11/06/real_estate/home_prices.fortune/index.htmGood solid article utilizing price-to-rent ratios to forecast home prices based on reverting to the mean as all the air flows out of the bubble.

There are only two rooms in the upstairs townhouse that are getting low air flow.

Some of the really old homes have them and they really do work at providing some airflow and extending minimizing the need for heat and air in the spring and fall.  

Once you know the cause of the leak, you can address it: be it a new roof, or getting some roof vents installed/repaired, cleaning gutters, or removing access insulation that blocks airflow from your attic...if there is mold - call a company that will take care of it.

@Derek Robinson,I used to live in a home exactly like that and ventilation / air flow is the key.  

(grin)The PLUS of a two door is the air flow and need less exhaust fan to dry out during and after shower times.All I see in the change is your making the bath smaller and taking bath closet for master space.