Position oven rack in bottom third of oven. Preheat to 400F. Spray 2 8 × 4-in. loaf pans. Stir flours with baking soda, herbs and salt in a large bowl until combined. Using your fingers or a pastry cutter, work butter into flour mixture until coarse crumbs form. Stir in cheese. Pour in buttermilk and stir just until combined.
Transfer dough to a well-floured surface. Divide dough in half. Shape each portion into a loaf about 7 in. long. Place in prepared pans.
Bake in bottom third of oven until tops of loaves are deep golden, 35 to 45 min. Remove to a wire rack to cool for 10 min. Run a knife around inside edge of each pan, then turn loaves out onto rack to cool completely. Soda bread keeps well for up to 2 days.