Backdraft dampers are a solution to help fight against high humidity and the effects of negative pressure inside your home. As we run our dryers, bathroom exhaust, and kitchen range vents, we are taking indoor air and pushing it outside. That leaves our homes under negative pressure. When our HVAC system turns on, it is pulling more air out of our homes and sends it into our ductwork. If our ducts are not sealed properly, we are losing even more air which creates a greater negative pressure within our living space and exacerbates the issue.
To compensate for that negative pressure, the air is pulled into the house through leaking doors and windows, electrical outlets, lights and fans, and other areas where hot and humid air can enter from the wall and attic space. When our exhaust vents are not running, there is also air being pulled back into our homes from that piping. That air is high in humidity and not conditioned. All of that can lead to uncomfortable spots within the home.
A solution would be the installation of backdraft dampers on the exhaust venting. Along with other steps like making sure the ducts are sealed, the envelope of the home is sealed, and adding a fresh-air intake, adding backdraft dampers can stop the infiltration of unconditioned outdoor air into the home through exhaust venting. Backdraft dampers will allow the exhaust fans to work as they should but will close the venting off when the exhaust fan is not in use.