Many historic tax credit (HTC) developments involve the construction of an addition onto a historic building to accommodate a proposed programmatic use. Construction of additions is often possible in a HTC project, so long as there is demonstrated need for an addition and provided the addition is designed in a manner that preserves the character of the historic building and is appropriate in the overall context of the site. Of particular importance are the criteria that the National Park Service (NPS) uses in evaluating proposed designs to determine whether an addition is appropriate for a historic building.