Depending on the size heat mat and the size of the hide it should work as long as its kept around 80. The substrate in the hide will have to get misted every few days or more then mixed to keep it moist, that will keep your humidity in the hide right where you want it. If the heat mat is heating up the hide too much, it can be put on a rheostat to control it.(around 80) The rest of the enclosure should remain dry especially the basking area, If the enclosure is big enough I would bring the basking area up to 95 and the tort will bask where he finds comfortable.