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Solving the Challenge of Dryer Makeup Air in a Tight Home Envelope
Read Time: 3 Minutes
Airtight home construction has become a standard in high-performance building, offering increased energy efficiency, enhanced indoor air quality, and greater comfort. However, as homes become tighter, mechanical ventilation strategies must evolve to account for all exhaust sources—including some that are often overlooked. One of these is the clothes dryer, which can expel a significant amount of air from the home.
The Overlooked Need for Dryer Makeup Air
Travis Brungardt of Catalyst Construction encountered this challenge while working on a high-performance home in Platte City, Missouri. The home features a well-sealed building envelope, measuring 0.4 ACH (air changes per hour), compared to the regional average of approximately 4 ACH in Kansas and Missouri. It also includes a three-zone HVAC system. While planning the ventilation strategy, Travis recognized that the dryer—an appliance typically selected by the homeowner rather than the builder—could introduce unintended complications.
Clothes dryers remove air from the home when exhausting moisture from laundry, creating negative pressure. In an older, leaky home, replacement air finds its way in through cracks and gaps in the structure. In a tight home, however, the exhausted air must be intentionally replaced to prevent issues such as pressure imbalances, backdrafting, or reduced efficiency of the HVAC system.
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Developing a Controlled Solution
With the home’s exceptionally tight 0.4 ACH building envelope, relying on uncontrolled infiltration for makeup air was not an option. Exhausting air from the dryer would create significant depressurization, potentially affecting indoor air quality and overall system performance. To prevent this, Travis implemented a simple yet effective solution—an inline duct fan designed to supply dryer makeup air, ensuring balanced airflow whenever the dryer operates.
The system consists of the following components:
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FG6 inline fan
Provides approximately 150 CFM of outdoor air.
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RSK damper
For backdraft prevention.
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ACCS 40
current switch
Detects when the dryer is running and activates the fan.
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FC 6 fast clamps
Securely mounts the fan within the duct system.
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Ducting and terminations
Installed to ensure proper air distribution and minimize any impact on other systems.
Instead of supplying air directly to a space, Travis opted to route the makeup air through the return duct of the home’s comfort system. This approach integrates outdoor air with conditioned air, reducing temperature swings and improving occupant comfort. However, this setup requires careful consideration of how it interacts with the HVAC system.
One potential improvement to this design is the addition of a motorized shut-off damper. This would allow the makeup air duct to close when the dryer is not in use, preventing unwanted airflow and maintaining the integrity of the building envelope.
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Inline Fans Offer Flexible Solutions in Residential Construction
This project highlights the versatility of inline fans in addressing ventilation challenges in modern homes. Whether solving dryer makeup air, integrating fresh air into a home’s ventilation strategy, or mitigating pressure imbalances, inline fans offer a reliable and adaptable solution.
If you are building a high-performance home with a tight envelope, you should consider dryer makeup air as part of your whole-house ventilation strategy. As air-tight construction becomes more common, ensuring balanced ventilation will be essential for maintaining IAQ and the efficiency of home appliances.
Useful Links:
U.S. Department of Energy: Air Sealing Your Home
U.S. Department of Energy: Detecting Air Leaks
ASHRAE Ventilation Standards: Standards and Guidelines