Why you should use the Moisture Flow Soffit Vent System

Soffit Cool Air Intake

There are three standard methods of venting bathroom exhaust fans in residential and commercial structures as approved by The International Code Council, state, and local building codes: through the soffit, roof, or gable.

These organizations have overlooked the monetary and health costs associated with the effects of these venting methods over time.

Eave Vent
Eave Vent

Soffit Venting

Although venting to a soffit is a common method of venting, it is a NOT an effective method of keeping the exhausted air out of the home.  Existing soffit vent terminations exhaust the air from the bath fan within the soffit’s passive air stream, making it very easy for the exhausted air to circulate back into attic.  According to the Department of Housing and Urban Development, this causes billions of dollars in structural damage annually.  The soffit is a passive air intake designed to work in tandem with a high ventilation method (ridge vent, mushroom vents, gable vents, etc.).  Existing soffit vent terminations do not displace the exhausting air out of the passive air stream that a soffit is designed to intake as part of a roof deck ventilation system.  Venting to a soffit may be the only method of venting under the right structural and codified conditions.  However, if a bath fan exhaust terminates at the soffit using existing vent terminations, then the moisture from the exhaust vent will remain in the soffit’s air stream, thus moving the moisture back into the attic. This can create conditions that cause mold formation, cause structural damage, attract insects and decrease indoor air quality.


Roof Venting

Venting to a bath fan to the roof perpetuates several problems that the Moisture Flow Soffit Vent has been engineered to solve. Roof Venting is another common method of venting a bathroom exhaust fan according to code. However, there are various disadvantages to venting to a roof.  Venting a bathroom fan to a roof can void a roof warranty (cutting into the roof to install the vent termination).  Venting to a roof may be impossible or impractical based on roofing material (steel roof, cedar shake, ceramic).  Homeowners’ Associations often do not allow venting through a roof, limiting association members’ options for code compliant venting.  Gasket or flashing failure and/or improper installation of the termination point may result in bulk moisture intrusion into the attic (roof leak).  Upward venting requires more energy than downward or horizontal venting, resulting in unnecessary energy consumption.

Roof vents displace the moist exhaust air directly onto the roof and over time will damage the shingles. Venting to a roof termination is an upward venting system.  Up venting works against the laws of physics, specifically gravity, which will require more energy over time to exhaust properly.  Up venting to a roof termination also subjects the transition duct to stack effects, which promotes moisture condensation in the transition duct.  Condensation in the transition duct can cause ceiling stains, degrade attic insulation, promote mold growth and decrease indoor air quality. Over time the moisture in the stack will eventually, through condensation, rust out the bathroom fan’s motor.


Roof Vent
Side View of the creation of Black Mold

Side View - Roof Vent


Gable Venting

Gable Venting a bathroom exhaust fan through a gable wall is a common method of venting.  It is an effective method of displacing moisture to the exterior of the home when the correct conditions are in place.  This method of venting is dependent on a structure having a gable wall.  Inner townhome units and homes that have a roof assembly that do not have gable walls cannot use this method of venting.  The effectiveness of inhibiting moisture to flow back into the attic is dependent upon the termination’s placement in relation to gable vents.  If a bathroom fan is a significant distance away from one of the gable walls, then venting to a roof or soffit is ideal.  Length of transition duct directly impacts effective displacement of moisture out of the attic.

Gable Vent, Inadequate ventilation causing mold
Moisture Flow Soffit Vent eliminates good money chasing bad money

Don't Have Good Money Chase Bad Money

The ICC and the state and local building codes that adhere to the ICC Standards are treating the problem of remediation, and the result of improper venting. The Moisture Flow Soffit Vent treats the source of the problem, which will stop the cycle of good money chasing bad money.



The Moisture Flow soffit venting solution is an adapted termination that effectively displaces moisture out of the home and inhibits moisture from flowing back into the attic. This groundbreaking design displaces the moisture outside the soffit’s passive air stream, moving the moisture from the bathroom fan exhaust safely and responsibly away from the home.  The implications of this product are significant, giving building professionals and homeowners a safe and effective way to vent through their soffit.  The Moisture Flow Soffit Ventis used in conjunction with an existing bathroom fan system or any other exhaust fan. The Soffit Vent adapts to the existing insulated ductwork of the bathroom fan and replaces the existing soffit vent in place. The soffit vent terminates just above the gutters on the building, thus displacing the exhausted moist air out of the soffit airstream, eliminating the potential for moisture air flowing back into the attic.

The Moisture Flow Soffit Venting System is revolutionary in more ways than one.  This is the only product on the market today that intentionally displaces moist exhaust air out and AWAY from the building assembly.  The unique design of the Moisture Flow Soffit Vent not only effectively displaces the moisture but it does not throw the moisture in the direction of the building assembly.  Existing roof, gable, and soffit vent terminations do not effectively keep the exhausted air away from the building assembly.  Our team considered this a critical design feature, as moisture is one of the leading causes of damage in buildings and homes.  Housing investigations.com states that moisture is responsible for billions of dollars in damage every year to homes.  Our team not only wanted to effectively remove the moisture, but we wanted to ensure it had as little interaction with the exterior assembly as possible.

Unlike a gable or roof vent, the Moisture Flow Soffit Vent is a down venting system.  Down venting, rather than up venting, works with the laws of physics rather than against them.  Our soffit vent is down venting and works with gravity to help the fan discharge moisture. Working with gravity, rather than against gravity helps conserves energy, saves money, and promotes longevity of the bath fan.  Down venting also helps prevent condensation in the bath fan’s transition duct because stack effect is no longer acting upon that duct.

Our team at Moisture Flow LLC. considers displacement away from the assembly, and not on it, superior engineering.