By Brian Fraser, AIA
High-rise construction is a massive undertaking in every aspect. Through collaboration and careful decision-making, a team can establish a well-designed, coordinated, and successful process that can save both time and money. Clear coordination and careful planning, from the earliest stages of development, are critical factors for a smooth and successful build in what is usually a complex process involving different factors and many stakeholders.
Structures at this scale require extensive forethought and consistent organization to keep the final product true to the design intent. This necessitates early interventions to avoid potential conflicts. Unit layouts offer a very good example of how these systems nest. If the design team wants to optimize the space for the best possible resident experience, it needs to consider construction documents (CD) details in their early discussions to facilitate that. As a hypothetical example: the placement of a mechanical closet in Unit A has ramifications for the position of the ductwork relative to the kitchen and the living room. It is not just about layout—it is about how the structure, the living space, and the mechanical infrastructure intersect. Time spent in discussing these details will have an exponential yield in saving time over the project’s lifetime.
To give a first-hand account of the impact of early level coordination on the life of a project, the following discussion will center around two different buildings: The Vermeer in Washington, D.C. and The Ellis in Charlotte, North Carolina. In this typology, everything starts early, from decisions on the mechanical systems, to alternative energy programs, to the location of the columns—they need to be locked down earlier. Decisions affect design, which affects decisions. An illustrative example of this kind of ripple effect comes from the author’s experience on working on The Ellis.
Design considerations for The Ellis
Selecting the building’s HVAC system early in the design process is important, as it will drive many design considerations moving forward. This article will review the design considerations and challenges that came after the team decided to move forward with split system heat pumps for the dwelling units early in the design process. This was a decision that brought cost benefits to the project, but also constructability challenges. The two main challenges were allocating the square footage to accommodate the required number of condensing units, and the line set not reaching 33 stories in length.
Line sets are copper piping that carry refrigerant from the outside condenser unit to the evaporator coil of the inside unit. There are maximum lengths for line sets depending on the unit and manufacturer, and this maximum length controls how far the exterior condensing unit can be from the interior system within the dwelling unit. Both vertical and horizontal distance must be factored in, and when the building is hundreds of meters (feet) in height, and has minimal roof area due to amenities for the residents, knowing that length is essential.
