The key to this moisture problem may be under the house. All earth should be covered by +6 mil plastic vapor retarder. The plastic should have enough gravel to make it lie tightly to earth and prevent an air space under the plastic. If you live in a green grass climate, during the summer the vents should be closed. Monitor the % RH in the crawlspace and home, when the % RH goes +60%, operate enough dehumidification to control humidity. EPA suggest 50% RH. Caution with mold, you may develope sensitivities that can make you ill.