What Building Energy Performance Means
Building energy performance is the measurement of how efficiently a building uses energy to deliver its operational functions — heating, cooling, lighting, ventilation, equipment operation, and vertical transport. It is expressed as Energy Use Intensity (EUI): total annual energy consumption divided by gross floor area (kWh/m²/year).
Applicable Standards
| Standard | Scope | Publisher |
|---|---|---|
| ASHRAE 90.1 | Energy Standard for Buildings (minimum efficiency requirements) | ASHRAE |
| ISO 50001 | Energy management systems — Plan-Do-Check-Act | ISO |
| ENERGY STAR | Energy benchmarking and labelling for commercial buildings | US EPA |
| ASHRAE Level I/II/III Audits | Energy audit procedures — walk-through to investment-grade | ASHRAE |
| LEED v4.1 EA Credits | Energy performance credits — efficiency + renewables | USGBC |
Key Energy Metrics
| Metric | Good Practice (Office) | Average | Poor |
|---|---|---|---|
| EUI (total) | 100–150 kWh/m²/yr | 150–250 kWh/m²/yr | > 300 kWh/m²/yr |
| HVAC share of total energy | 35–45% | 45–55% | > 60% |
| Lighting power density | 8–10 W/m² (LED) | 12–15 W/m² | > 20 W/m² (old fluorescent) |
| Chiller efficiency (kW/ton) | 0.55–0.65 (water-cooled) | 0.70–0.85 | > 1.0 |
| Cooling tower approach (°C) | 3–5°C | 5–8°C | > 10°C (fouled) |
| AHU specific fan power | ≤ 1.6 W/(L/s) | 1.6–2.5 W/(L/s) | > 3.0 W/(L/s) |
| Power factor | ≥ 0.95 | 0.85–0.95 | < 0.85 (penalty) |
Typical Office Energy Breakdown
- HVAC: 40–55% — cooling is dominant in tropical climates like Bangladesh
- Lighting: 15–25% — LED retrofit is the highest-ROI energy measure
- Equipment/plug loads: 15–25% — computers, printers, kitchen equipment
- Lifts & escalators: 3–8%
- Domestic hot water: 1–3%
- Other (pumps, fans, security, IT): 5–15%
Top Energy Saving Measures (by ROI)
| Measure | Typical Saving | Payback |
|---|---|---|
| LED lighting retrofit | 40–60% of lighting energy | 1–3 years |
| HVAC scheduling optimization | 10–20% of HVAC energy | Immediate (BMS settings) |
| Chiller plant optimization | 15–25% of cooling energy | 1–2 years |
| VFDs on pumps and fans | 20–40% of motor energy | 2–4 years |
| Building envelope improvement | 10–15% of cooling energy | 5–10 years |
| Solar PV (rooftop) | 5–15% of total energy | 5–8 years |
| Occupancy sensors for lighting | 20–30% of lighting in common areas | 1–2 years |
Bangladesh Context
- Electricity tariff for commercial buildings: BDT 9–12/kWh (2024). Rising tariffs make energy efficiency increasingly cost-effective.
- Cooling dominates energy use — improving chiller efficiency and reducing solar heat gain have the highest impact.
- Sub-metering is rare in Dhaka buildings — without sub-metering, energy management is guesswork.
- Grid emission factor: ~0.55 kgCO₂/kWh — every kWh saved also reduces carbon by 0.55 kg.
- Solar PV potential is good (4.5–5.0 kWh/m²/day average solar irradiance) but adoption on commercial buildings remains low.
References
Insights & Guidance
- EUI (Energy Use Intensity) is the primary metric: 100-150 kWh/m²/yr is good for offices; >300 is poor.
- HVAC accounts for 40-55% of commercial building energy in tropical climates — the biggest savings opportunity.
- LED retrofit has the best ROI: 40-60% lighting savings with 1-3 year payback.
- Sub-metering is essential for energy management — without it, you're guessing.
- Bangladesh grid factor ~0.55 kgCO₂/kWh — every kWh saved is 0.55 kg carbon reduced.
- ISO 50001 provides the management system framework for continuous energy improvement.
Energy is typically the largest controllable operating cost in a commercial building — 30-40% of total operating expense. In Bangladesh, with rising electricity tariffs (BDT 9-12/kWh), the financial case for energy efficiency is compelling. Beyond cost, energy performance directly determines carbon emissions, ESG ratings, and green certification eligibility. Investors and MNC tenants increasingly require energy performance data.
- Rising energy costs — without efficiency measures, energy bills escalate with tariff increases.
- Stranded asset risk — poor energy performance reduces asset value as green requirements tighten.
- Tenant attrition — MNC tenants leave for energy-efficient buildings to meet corporate ESG targets.
- Equipment failure — inefficient systems run harder, fail more frequently, cost more to maintain.
- No data — without metering and tracking, energy waste goes undetected for years.
- 12+ months utility bill data (electricity, gas, diesel for generator)
- Sub-metering data for major systems (HVAC, lighting, plug loads)
- Energy audit report (ASHRAE Level I minimum)
- EUI calculation and benchmarking
- Energy management plan with targets and measures
- BMS trend data for HVAC performance
- Lighting type — LED, fluorescent, or older technology?
- Lights/HVAC in unoccupied areas — are they on?
- Sub-meters — do they exist? Are they read and recorded?
- BMS — is it actively used for energy management or just alarm monitoring?
- Solar panels on roof? Energy dashboard displayed?
- What is the building's EUI in kWh/m²/year?
- Is there sub-metering for major systems?
- Has an energy audit been conducted? What were the recommendations?
- What energy-saving measures have been implemented?
- Is there a BMS? Is it used for energy optimization?
- What is the annual energy cost (BDT)?
- Energy audit — certified energy auditor for ASHRAE Level I/II audit.
- HVAC optimization — MEP engineer for chiller plant and air-side optimization.
- Solar feasibility — solar PV consultant for rooftop assessment.
- ISO 50001 — energy management consultant for certification.