Air flow through your house - think about where the return air inlets (registers) are located. How is return air flow affected by bedroom and other doors being open or closed?

Supply air (heated or cooled) is only part of the air handling system. Every cubic foot of air that comes into a room from a heating vent must displace another cubic foot of air that effectively ‘leaves’ the room. Think about how air flows into and out of each room, during daytime and at night.

For the hallways and common/open areas, cooler air will generally ‘fall’ down a staircase while warm air tends to float upwards.

Continuous fan forced air flow through the building tends to mix the air and create more even air temperatures. One method is to set the furnace fan to run continuously on a low speed, forcing the house air to move around and stir, mixing the warmer air with cooler air from elsewhere.

It is not unusual to discover that the ‘cold air’ return vents and ducts are poorly located, too small, have incorrect air flow ratios, or do not properly service some rooms when doors are closed.

I would look first at balancing the air flows such that air temperatures in various rooms are close to matched. When the furnace is actively heating, there may be areas that get warmer, faster. Keeping the circulation fan running should bring the rooms back into temp balance.

I have a whole house air exchanger, which exhausts a steady but modest air flow out of the building while simultaneously drawing in outside fresh air. The heat exchanger transfers most of the warmth from the exiting air into the incoming air flow.

It is common to connect this sort of heat exchanger into the furnace return air ducting, but it can also be ducted directly to specific rooms. In my current and previous houses, the unit draws house air directly from a wall or floor duct in a common area room. Outside air is heat transfered and then flows into the cold air return, mixing with general return air flow from the rest of the house.

Some ventilators can be run on a cycle, such as 20 minutes of each hour. I rigged my furnace circulation fan to run on low whenever the ventilator was running, stirring the house air frequently without running the furnace fan 24/7.

The furnace circulation fan keeps the air inside the house moving, not only reducing temperature differences between areas but also distributing the incoming fresh air. A properly installed air/heat exchanger greatly reduces the difference in smell between outside air and inside air. When I walk into my house, the air does not smell like ‘inside’, it has the same overall freshness as outside. Cooking odors fade within hours. A good kitchen fan exhaust the bulk of cooktop emissions, but if you walk in the front door in the evening and can tell what was cooked for dinner a few hours earlier, a ventilator can make a difference.