Transforming a humid or damp basement into a dry healthy space can have a huge impact on the air quality throughout the entire house. Whether you plan on finishing your basement or not, it shouldn’t be ignored. Because of the natural “stack” effect that occurs in all homes, air will rise from the lowest level and vent out at the top. Even with conditioned air from an HVAC system running in a house, as much as 40% of the indoor air we breathe originates from the basement or crawlspace of the house.


If you see signs of water penetration and dampness on the floors and walls, the first step towards a healthy basement should be a drain system. This will have the biggest impact when dealing with moisture problems in a basement. With a french drain system in place, vapor barriers, masonry coatings, and dehumidifiers will also see improved performance. The drain system will work to reduce hydro static pressure and vapor transmission.

Humidity & Air Quality

If you do not see signs of water penetration or dampness in your basement, or you already have a drain system and it still feels damp or humid then the next step should be dehumidification and ventilation. For most people we recommend either dehumidification, or dehumidification with ventilation. Take care when choosing a dehumidifier. Most off the shelf dehumidifiers are not designed to operate at under 70°F. When placed in a cool basement or crawlspace they will spend a lot of their time in “defrost” mode instead of dehumidifying. Pick a properly sized dehumidifier, designed to operate 24/7/365 in cool basements or crawlspaces with at least a 5-year warranty.

Adding a ventilation system such as EZ Breathe or other similar ventilation systems will reduce the stack effect and pull healthy air from the main level into the basement and reduce the amount of basement air that makes its way to the main level. These systems are also proven to reduce airborne particles (i.e. mold), gasses (i.e. radon), and VOC’s. Because these systems rely on pulling less humid “conditioned” air from the upper level to reduce humidity levels, we recommend using a dehumidifier in conjunction with systems like these. The dehumidifier will turn on when the supply air that’s being pulled into the basement is not dry enough.

Vapor Transmission

In certain cases, you may want to use a masonry coating (we use MasterSeal 581), or a vapor barrier. When going with a masonry coating, be careful. Cheap masonry coatings are prevalent and do not form a strong enough bond to the walls. Unless your walls stay relatively dry year-round, most coatings will fail, usually within 1-3 years. Coatings such as MasterSeal 581 will only slow down and reduce vapor transmission through the wall.

Sometimes vapor barrier encapsulation is necessary. This traps the vapor transmission between the interior wall and the vapor barrier. The barrier must be designed to direct this trapped water to a drain system. This should only be done on walls that are constantly damp and waterproofing from the exterior in not a realistic option.

Do not install a vapor barrier or masonry coating without a dehumidifier. Condensation that forms on the walls and floors will be trapped on the interior side of the barrier / coating.