American Arborvitaes grow to a perfect 20 ft. They make a wonderful screen between houses, blocking out the house, but not the whole sky. Your yard will still get plenty of sun.
Mature Height . 20-25 ft
Mature Width . 4-10 ft
Sunlight . Full Sun to Partial Shade
Growth Rate . 1-2 ft/yr
Botanical Name . Thuja Occadentalis 'Nigra'
Hardiness zones . 5-9