HVAC, Lighting, and Building Energy Systems
HVAC systems
Understand the seasonal efficiency metrics: for heat pumps SCOP/SPF; for boilers seasonal efficiency; for chillers SEER. Key concepts: part-load behaviour, distribution losses, hydronic balancing, pump and fan affinity laws (flow ∝ speed, power ∝ speed³), and heat recovery ventilation. Control matters: weather compensation, zoning, setpoint discipline, and night setback often deliver savings cheaper than equipment replacement.
Lighting
Metrics: luminous efficacy (lm/W), illuminance (lux), and LENI (kWh/m²/yr) for whole-building lighting. Measures: LED retrofit, occupancy/daylight sensors, task lighting, control gear. Traps: replacing lamps without addressing over-lighting or controls; ignoring lighting power density limits and glare/quality requirements.
Other building systems
Domestic hot water (distribution losses, recirculation, solar preheat), lifts, and plug loads. Energy management and building automation (BACS) can unlock savings across systems; the BACS energy-efficiency class is a recognized concept.
Traps in questions
Confusing kW (power) with kWh (energy); applying the cube law to the wrong quantity; assuming a heat pump's COP at rated conditions equals seasonal performance (cold-climate degradation matters); forgetting that ventilation heat recovery changes the balance of heating demand.
Worked example
A pump runs 4,000 h/yr at 11 kW. Reducing speed to 80% via a VFD: power ≈ 11 × 0.8³ ≈ 5.6 kW, saving ≈ 5.4 kW × 4,000 h ≈ 21,600 kWh/yr. Affinity laws make variable-speed control a high-value measure.
Rule of thumb
Controls and commissioning first, then equipment. Measure part-load reality before sizing replacements.