Building Systems and Technology: Sizing and Integration
This domain tests structural, mechanical, electrical, plumbing, fire, and vertical transportation systems at the planning level: enough to size space, set floor-to-floor height, and coordinate the building.
Structural systems
- Gravity loads travel from slab to beam to column to foundation. Lateral loads travel through diaphragms into braced frames, moment frames, or shear walls.
- Rules of thumb: steel beam depth near span/20; concrete bay sizes commonly 24 by 24 feet, steel 30 by 30 feet. Longer spans buy planning freedom and cost more.
- Framing layout should align with the architectural module rather than fighting it.
Mechanical, electrical, plumbing, and fire
- HVAC options: variable air volume all-air systems for offices, fan-coil or chilled-beam systems where plenum depth is tight, packaged rooftop units for low-rise. Mechanical rooms and shafts need central, stacked real estate.
- Plumbing: group toilets near a riser, size fixture counts from occupant load, and locate water heating in the core.
- Electrical: service entrance, switchgear and transformer rooms, and electrical closets stacked floor to floor.
- Fire protection: sprinkler riser and standpipes in stairs, alarm panel, and smoke control where required. Elevators: car count and speed from population and handling capacity; machine-room-less options save core space.
Worked example
A four-story office at 20,000 square feet per floor plate. Using a planning load of 400 square feet per ton, each floor needs 20,000 / 400 = 50 tons, or 200 tons total. Two 100-ton chillers provide redundancy. At roughly 2 square feet per ton of mechanical space, the chiller plant needs about 400 square feet, preferably at roof or basement level with a vertical shaft. The shaft, risers, electrical closets, restrooms, and elevators together typically consume 15 to 25 percent of each floor plate, which is why core planning precedes space planning.
Traps that cost marks
- Confusing a ton of cooling (12,000 Btu per hour) with kilowatts.
- Assuming sprinklers eliminate all fire-resistive construction requirements.
- Setting floor-to-floor height before knowing plenum and structure depth.
- Hiding shafts in the middle of leasable space instead of stacking them.