what andrew siad. wet heat can be achieved in a domestic oven a number of ways
1 put a roasting pan in bottom of oven when preheating then when placing bread into oven pour a kettle of boiling water into siad tray creating a woosh of hot steam (so be carefull) that will keep the humidity up
or
2 place a roasting pan filled with bbq lava rocks in bottom of oven before preheating and add the boiling water same as option 1 the lava rocks hold the heat so dont lead to such a drop in oven temp
spraying the sides of the oven with water from a garden sprayer (for houseplants) during baking is another way to acheve moist air . just try not to open the oven door to much or for too long as heat will escape