Building Services
What the domain tests
Building Services tests whether you can integrate water, drainage, HVAC, electrical and fire systems into the architecture without compromising safety, maintenance or ceiling heights.
Core rules
- Water supply: domestic demand is often taken as 135-200 litres per capita per day; check the local authority. Size storage for at least one day, provide booster pumps and prevent backflow.
- Drainage: use fixture units, traps with 75-100 mm water seal, soil and waste stacks, a vent stack and manholes at changes. Give horizontal pipes adequate fall and discharge to a septic tank, soak pit or sewer.
- HVAC: one ton of refrigeration = 3.517 kW = 12,000 BTU/h. Cooling load is estimated in W per sq m and then checked against air changes and fresh-air requirements. Fire dampers are needed where ducts cross fire compartments.
- Electrical: Pakistan uses about 230 V single-phase and 400 V three-phase at 50 Hz. Prepare a load schedule, earth properly, use RCD protection and provide emergency lighting.
- Fire: detection, alarm, hydrants, sprinklers, extinguishers, protected exits, travel distance and compartmentation must work together.
Worked example
A 200 sq m office has an estimated cooling load of 150 W/sq m, so 200 x 150 = 30,000 W = 30 kW. Divide by 3.517 to get 30/3.517 = 8.5 TR. Add 10% for duct gain and diversity, giving about 9.4 TR, so select two 5 TR units rather than one unit running at full load.
Traps that cost marks
Confusing kW with tons of refrigeration. Ignoring diversity. Omitting vent pipes. Undersizing tanks. Missing fire dampers. Measuring exit width incorrectly or ignoring accessible sanitary facilities.