Hyman's company often uses a wall-mounted air exchanger made by Humidex, which vents cooler, damp air to the outside. Air-conditioning naturally lowers moisture levels in the air. Yet another option is to add dehumidifiers, but there are several drawbacks to them. They are more expensive to run than a ventilation fan, and unless a dehumidifier is plumbed directly to a drain line it will have to be emptied periodically. And, as Heim points out, dehumidifiers tend to be noisy.
Fresh air is just as important to boilers, furnaces and gas-fired water heaters as it is to people.
These devices often are enclosed in a small mechanical closet. But in doing so, builders will have to add a source of fresh combustion air. There's a lot to think about when converting a basement into a bright, inviting living area. But once the work is done, you'll never want to leave. Click here for books about room decoration.