Or you can consider forced air ventilation (our home ventilation system)
An alternative to sub floor ventilation if access is restrictive is forced air ventilation. This is also an excellent system to use in conjunction with sub floor ventilation to create a consistent environment of fresh, dry, healthy air throughout your home.
Air is drawn into the roof space, where it is filtered, and heated if necessary, before being evenly distributed throughout the home. As well as fighting musty smells by distributing clean, dry air throughout the home, this can also reduce heating bills by harnessing radiant heat trapped in the roof space.