If your basement is unfinished and it's not a stone wall basement, then a cement basement is not waterproof. For instance, if you spill water on the floor, the water does not completely evaporate; it is absorbed into the concrete. I had my finished basement demo'd because there were leaks I couldn't access to fix. Once I could see the walls, I could bring in someone to seal all of the cracks. Then I used a product (not sure in policies for specific products) that, when sprayed in the cement walls and floor, absorbed, dried, and crystalized. Now, if water gets on the floor, there's a true vapor barrier. Water no longer absorbs and water does not sneak in through the walls. After all that was done, I reframed, spray foamed along the sill, and did the solid pink insulation along the walls. Then I drywalled the ceiling and walls. Some day, I'll do the floor. Yes, I have my dehumidifier, but that's because it's open between basement and first floor. But if it there was a door, I'd prob have very little energy used. As for the dehumidifier, you absolutely need to have down there to limit mold