Ventilation is very important in this circumstance as mentioned above.
Mould is best controlled by ventilation, either active or passive, depending on how bad it becomes.
If both are possible maybe try passive initially and have an active system for use as backup if he humidity suddenly causes issues.
Although it may be best to find out why the humidity increases if that happens.
Is the ground moist?
Would the humidity and thus mould be coming from the exposed sol, venting should fix that.
Sealing the floor would not help since any ground moisture would just come through he walls if the floor was sealed.
This may help;
moisture in basements