OBC Building Services cheat sheet

Building services covers mechanical, electrical, plumbing, fire protection and vertical transport systems that make a building safe, habitable and functional.

Model codes (e.g. IBC, IMC, IPC, NEC, NFPA) establish minimum requirements; the locally adopted edition and amendments govern in a conflict.

Occupancy classification drives egress, fire protection, ventilation and fixture requirements; a mixed-use building may carry multiple classifications.

Load calculations must precede equipment selection: heating and cooling loads via accepted methods (e.g. ACCA Manual J or ASHRAE methods), not rules of thumb.

Design documents typically require coordination drawings showing spatial and clearance conflicts among trades before installation.

Commissioning verifies that installed systems meet design intent through documented functional performance testing.

Clearances and access panels are code items: equipment must be serviceable without demolishing finishes.

As-built drawings record actual installed conditions and are the baseline for future maintenance and alterations.

Permits and inspections are sequenced by trade; concealed work must be inspected before it is covered.

Sensible heat ratio = sensible load / total load; total load = sensible + latent, and coil selection must match the space SHR.

Airflow: cfm = Btu/h ÷ (1.08 × ΔT) for standard air; 1.08 bundles air density, specific heat and 60 min/h.

Duct sizing by equal friction or static regain; velocity limits control noise (roughly 1,200-1,500 fpm in main trunks for low-velocity systems).

Water pipe sizing uses fixture units per code tables; pressure must overcome static height (0.433 psi per foot of rise) plus friction.

Domestic hot water storage and recovery must match peak demand; recirculation limits wait time and scald risk.

Electrical: watts = volts × amps × power factor for single phase; three-phase power = √3 × V × I × PF.

Voltage drop should be limited (commonly 3% branch, 5% total) to protect equipment performance.

Grounding, bonding and GFCI/AFCI protection locations are code-mandated, not optional design choices.

Panel schedules and load balancing keep neutral currents and phase imbalance within limits.

Means of egress has three parts: exit access, the exit, and exit discharge; each has separate requirements.

Egress width is computed from occupant load using code factors (e.g. 0.2 in per occupant for sprinklered, 0.15 in for stairways in common editions).

Travel distance and dead-end corridor limits depend on sprinkler protection and occupancy; sprinklers generally allow longer travel.

Fire-resistance ratings apply to structural elements, shaft enclosures and separation between occupancies.

Sprinkler systems are classified by hazard; design density (gpm/ft²) and remote area size define the hydraulic demand.

Standpipes, fire department connections and hydrant spacing support manual firefighting and must be coordinated with site access.

Smoke control uses pressurization, exhaust or compartmentation; stair pressurization keeps egress paths tenable.

Elevators require machine-room or machinery-space provisions, pit depth and overhead clearance per the applicable elevator code.

Elevator recall, standby power and firefighter service features are coordinated with the fire alarm sequence of operations.