Prevent mold with basement ventilation

In previous posts we’ve discussed the causes and solutions for mold in basements. Today we will provide more detail on how to prevent basement mold with ventilation and air conditioning, the main methods for reducing moisture content in the air.


Ventilation includes air exchanges and air circulation. Limited ventilation in most basements leads to damp, stagnant, smelly air, and will eventually lead to mold growth. Exchanging stagnant basement air for fresh outdoor air is one good way to ventilate a basement. This can be accomplished using a basement fan, but the space may also require dehumidification due to the introduction of humid outdoor air.

Air circulation within the basement can be improved by installing ceiling or room fans. The main objectives of ventilation are air movement and exchanging stagnant air for fresh air. The point of ventilation is not to filter or condition the air, but rather to replace, dilute, or move it around.


Air conditioning involves the process of modifying the temperature and humidity of the air to make it more acceptable. Heating, ventilation, and air conditioning, or HVAC, systems are used to control the temperature, and to some degree the humidity, of indoor air. Running an air conditioner in the summer not only cools the air, it also dries the air.

If you have an HVAC system that services the basement, you can help to prevent basement mold just by running it. There is a common misconception that basement HVAC systems are unnecessary because the temperature inside most basements stays relatively constant throughout the year. Remember, though, that temperature is only one of the two functions of air conditioning. If a basement stays closed up, unventilated and unconditioned, the temperature might be within the desired range, but the humidity may be significantly elevated. Mold can grow and odors can develop in a basement or living space of a home simply because the HVAC system has been turned off.

If the HVAC system is not running, then the air is not being conditioned or filtered. Without filtration, the air will accumulate dust, dirt, and mold spores that will create a bigger problem. We have conducted basement and entire home mold remediations where the only cause of mold growth was stagnant, humid air due to the fact that the HVAC system had been turned off.

HVAC Systems

The most effective, but most expensive, type of basement HVAC system is a centrally-located, ducted unit. This is the best system if you have a large basement and/or a basement consisting of multiple rooms with doors and walls that restrict airflow.

A cheaper but less effective alternative is a window mounted air conditioner/heater unit. Window units are better suited to smaller basements that do not have multiple rooms.


So how do you get the already cool humid air in a basement dry without cooling it further? The answer in most cases is a dehumidifier.

Dehumidifiers range from simple freestanding, single room units that plug into an existing receptacle, to whole-house (or whole-basement) built-in units that work in conjunction with the HVAC system. We will cover this in much more detail in subsequent posts.

How Branch Environmental Can Help

At Branch Environmental we provide comprehensive packages that address the air quality inside your home and basement. We have you covered from inspection to mold remediation to dehumidifier selection and installation. Call us today if you would like to schedule a basement assessment, indoor air quality inspection, or simply want more advice on how to prevent basement mold.