How a Jumper Duct Can Help

Most discussions of jumper ducts start with a question.  What is a jumper duct?  A jumper duct is simply a duct that allows air to flow from one room of a home to another, usually through the attic.

The answer to the first question usually leads to a second. Why do we care so much about air flowing from one room to another?  The answer to the second question is that a jumper duct can help make an uncomfortable room much more comfortable.

Improved Room Comfort All Year Long

In diagnosing home comfort issues throughout the St. Louis area, sometimes we find a home that has one particularly uncomfortable room. That room is usually too hot in summer and too cold in winter. The general cause for the discomfort is not always the same, but sometimes the culprit is an ample supply of warm air coming from the furnace combined with the lack of a path for return air back to the furnace.

Consider what happens in that uncomfortable room during winter. When the furnace starts to run, it blows warm air into the system of ductwork within the home. The air inside the ductwork builds pressure until it flows through the supply registers and into all the rooms.  The air flowing into each room pressurizes that room.

Once pressure builds inside each room, air starts to flow back through returns grills, into the ductwork, through the filter, and back into the furnace for re-heating. What happens in the uncomfortable room that has a supply register but no return grille?

In the uncomfortable room, air flows in and builds pressure. With no path for return air, the pressure in the room continues to build. Once the pressure inside the uncomfortable room becomes equal to the pressure inside the ducts, no more warm air flows into the room.

The furnace continues to run and supply warm air to the other rooms of the home until the set point of the thermostat is reached...then the furnace shuts off. Most of the house is warm, but the uncomfortable room is cold because it did not receive as much heat as the other rooms.

How Jumper Ducts Can Help

In this situation, the problem can be remedied by a jumper duct. The jumper duct allows air from the uncomfortable room to flow out and into another room containing a return. Once in the other room, the air can flow back to the furnace.  With a path established for return air, the previously uncomfortable room will receive warm air for the same length of time as the remainder of the rooms in the home.

Of course the same thing happens in the summer when a jumper duct can help an uncomfortably hot room receive the same amount of cool, conditioned air as the rest of the home.

Many things can cause a room to be uncomfortable. Sometimes a jumper duct can be just the right fix.