Efficient ductwork design ensures that the exact same volume of conditioned air entering rooms in your home through supply ducts also leaves through return ducts to be conveyed back to the air handler. This creates a condition of neutral air pressure in the house, the optimum state for effective heating and cooling and energy efficiency.
Often, however, home builders opted for just one central return duct to serve all rooms, usually located in a common area like a hallway. This ductwork design compromise cuts construction costs and also results in a loss of privacy — it only functions as long as all bedroom doors are left open at all times so the air path to the central return is unobstructed. What happens when doors are closed?
- Bedrooms become over-pressurized with air from the supply ducts. This forces conditioned air out of the house through cracks and gaps in the structure, wasting energy.
- Also, as warm, naturally humidified interior air is forced into wall voids through cracks, it encounters cold air and condenses, saturating internal structure, degrading wall insulation and creating a breeding ground for mold.
- Because more air leaves the air handler than returns, the air balance in the rest of the house is disrupted and rooms become depressurized. Cold outside air is drawn in through cracks and gaps, as well as air from unconditioned zones like the attic and crawl space. This causes the furnace to run longer to maintain thermostat settings and also impacts indoor air quality.
Strategies to avoid these drawbacks range from simple measures to expensive retrofits:
- Install air grilles in all bedroom doors so air has an unobstructed path to the central return.
- Install jumper ducts in the ceilings between all bedrooms connected to a vent in the hallway so air can be conveyed back to the central return.
- Install dedicated return air ducts and grilles in every room and route the ducts directly back to the air handler.
Comfort Systems has provided indoor comfort and efficiency for Wichita homeowners since 1996. Call us for more advice on ductwork design issues that may affect your home heating system.
Our goal is to help educate our customers in Wichita, Kansas about energy and home comfort issues (specific to HVAC systems). For more information about ductwork design and other HVAC topics, download our free Home Comfort Resource guide.