A built-in oven with upper and lower heat features 2 heating elements. Most ovens use these simultaneously as a combination, but there are also oven that let you separately control them. If you like baking pies or oven dishes, we recommend you turn on both elements at the same time. This way, you can make sure your dish properly rises, while the top and bottom are both evenly cooked. Do you specifically want a crispy bottom or crust? Set your oven heat with a single element: upper heat or lower heat.