Preheat the oven to 450 degrees F (230 degrees C).

Combine all-purpose flour, whole wheat flour, baking powder, sugar, and salt in a large bowl. Cut in cold butter with 2 knives or a pastry blender until the mixture resembles coarse crumbs; stir in buttermilk until just moistened.

Turn dough out on a lightly floured surface; knead gently 8 to 10 times. Roll out to about 3/4-inch thick. Use a 2 1/2-inch round biscuit cutter to cut biscuits; reroll any scraps to cut more biscuits. Place biscuits on an ungreased baking sheet.

Bake in preheated oven until biscuits are lightly browned, 10 to 12 minutes.