Building services and environmental control engineering (HVAC, plumbing and drainage, fire services, energy efficiency)
Building services is the largest applied domain. It tests whether you can select and size HVAC, plumbing, drainage, fire and energy systems to Hong Kong codes and then explain the trade-offs. Expect load calculations, air and water flow, trap seals, fire compartmentation and energy compliance.
Core rules and concepts
- HVAC: separate sensible and latent loads. Use psychrometrics for coil apparatus dew point and supply air. Chilled-water flow Q = load/(ρcpΔT). Part-load control matters: variable flow, VSD, staging and reset.
- Ventilation and smoke: car parks, plant rooms and kitchens need adequate air changes; stairwells and lobbies may need pressurisation. Smoke extraction must be tested with fire dampers and control modes.
- Plumbing: potable and flushing water are separate; provide storage, backflow prevention and anti-siphon protection. Control Legionella with temperature, circulation and dead-leg avoidance.
- Drainage: gravity flow needs correct gradients, trap seals and vent pipes. A trap without adequate venting will lose its seal under pressure fluctuations.
- Fire services: comply with FSD codes for sprinklers, hose reels, detection, alarm and emergency lighting. Compartmentation and fire dampers protect escape routes.
- Energy: BEEO Cap. 610 and the Building Energy Code set requirements for prescribed installations; OTTV controls envelope heat gain. BEAM Plus rewards beyond-code performance.
Worked example
An office zone of 100 m² has a sensible cooling load of 100 W/m². Supply air is 10 K below room temperature. Estimate supply air flow. Load = 100 × 100 = 10,000 W. Mass flow = Q/(cpΔT) = 10,000/(1.005 × 1000 × 10) = 0.995 kg/s. Volume flow ≈ 0.995/1.2 = 0.83 m³/s = 2,990 m³/h. Reasoning: the sensible load alone sizes the air for sensible cooling; latent load and outdoor air will increase the coil and fan duty. Check the result against typical face velocity and duct size.
Traps that cost marks
- Using total load with a sensible-only temperature difference.
- Mixing m³/s, m³/h and L/s.
- Ignoring outdoor-air latent load in Hong Kong.
- Forgetting fire dampers where ducts cross compartment walls.
- Designing domestic water without backflow or Legionella control.