How Do Subfloor Ventilation Systems Work?


Keeping the subfloor of the home well ventilated is critical to the health and wellness of the property as well as its occupants for a number of reasons. Millions of homeowners rely on subfloor ventilation system for this purpose. A properly designed, installed, and maintained ventilation system protects the subfloor area from a number of potential dangers including condensation, dampness, undesirable odors, mildew, mould, and other moisture induced concerns.

Moisture removal and proper ventilation has a significant impact on the overall indoor air quality of your home. However, it is important to note that just an interior ventilation system is not sufficient for this purpose. Dampness related issues in the home are not caused just by improper interior ventilation. In many instances, a wet under floor area is the main culprit for your moisture related problems. Though high interior humidity is extremely unpleasant and unhealthy, this could well be a symptom of a much larger problem under the building. This is why alongside adequate home ventilation, proper subfloor ventilation is also essential for a healthy home free from moisture, mould, and odor.

Working Principle of Subfloor Ventilation Systems:

The purpose of subfloor ventilation is to eliminate the moist air from the subfloor and replace it with fresh and dry air. The simplest way to accomplish this is to install numerous vents in the wall all over the building and rely on natural ventilation for under floor ventilation. Though this alternative is sufficient at times, it may sometimes require a helping hand.  Installation of subfloor fans will make ventilation more effective and allow a greater volume of moist air to be replaced from the under floor.

Subfloor fans create cross ventilation, extracting damp air from one side of the building through the subfloor and pulling fresh air from the building’s opposite end for increasing under floor ventilation.  Please remember that cross flow ventilation is effective only when the air enters from one side of the building and is extracted by the subfloor fans from the opposite side. Cross flow may not be an option if there are pockets preventing free movement of the air. In such cases, the fans can be ducted to one or more points for moisture extraction from specific damp and wet areas. Choosing the right areas for installation of the subfloor fans is an extremely important factor. Please remember that in order to remove air, availability of replacement air is important and this air enters the sub floor area via strategically positioned vents.

Types of Subfloor Ventilation Systems

There are many different types of subfloor ventilation systems, the most common variant being an air extraction unit capable of extracting moisture effectively from the under floor area. In these units, a negative pressure is created by the subfloor fans. As a result, replacement air is drawn in through the vents and other openings in the subfloor.

Ideally, a subfloor ventilation system should operate when the replacement air is sufficiently dry. During the daytime, the temperature is higher and relative humidity is lower. Therefore, it is always better to run these ventilation systems during the day and avoid using them during moist weather conditions. The most effective way to operate these systems is to have them solar powered. This will makes sure that the system only runs during the warmest and driest parts of the day.

In case of an old building, fan forced ventilation systems can be a good option because it doesn’t require any changes to the house’s external appearance. The primary function of these systems is to improve the airflow by initiating air exchange through a ducting system with fans and a timer.

In case of natural air cross flow systems with air vents, all the vents must be above the soil level and the entire sub floor space should not have any blockage that can disturb the passage of air.

The methods we have discussed so far are the most common and effective ventilation options for a subfloor. However, more customized ventilation methods can be devised to address your specific under floor dampness issues. If you are looking to obtain a more precise understanding of your home’s ventilation needs, it is better to have your subfloor area assessed by expert. The selection of ventilation method depends to a great extent on the specific concern areas you want to address and the size of your property. If you have a large property, the most preferred alternative is a ducted sub floor fan system. Otherwise, just a few sub floor fans or air vents may solve your problem by providing the required cross flow ventilation.

At ExtractAir, we have been instrumental in solving the most challenging subfloor dampness issues for many of our clients. If you are really serious about solving your subfloor issues for once and all, please contact our experts and fix your free appointment.