MU-27 (Naval Observatory). Second, the amendments seek to increase the height that dictates the set-aside amount from 50 feet to 85 feet. Currently, a building greater than 50 feet in height is subject to the lower IZ set-aside requirements (8% of the residential floor area or 50% of the bonus density utilized) to account for the increased construction costs of concrete and steel. Based on building code changes and technological improvements that allow for taller stick-built construction, OP aims to raise the threshold to 85 feet. This change would make buildings under 85 feet in height subject to the higher IZ set-aside requirements (10% of the residential floor area or 75% of the bonus density utilized).