ASHRAE 90.1 Appendix G Performance Rating Method is the standard whole-building energy modeling protocol for LEED v4.1 EAc1 + IGBC v3 EE-1 + many international tenant compliance. For Indian projects, Appendix G is layered over the local ECBC 2017 baseline. Done well, it captures full energy savings credit; done poorly, it loses LEED + IGBC points.
This guide walks the practical 8-step workflow for an Indian commercial project.
What Appendix G actually requires
Appendix G defines two models:
- Baseline (reference) building — built per ASHRAE 90.1 prescriptive requirements
- Proposed (designed) building — actual project design
Both modeled in same simulation tool with identical climate + occupancy + schedules. Energy savings = (Baseline – Proposed) / Baseline.
Step 1: Climate zone identification
Per ASHRAE 169:
- Mumbai = CZ 1A (Hot/Humid)
- Chennai = CZ 1A
- Delhi = CZ 2A or 3A (Mixed/Hot)
- Bangalore = CZ 3A or 4A (Mild)
- Pune = CZ 3A
- Cochin = CZ 1A
Climate zone drives baseline equipment efficiency requirements.
Step 2: System type selection (baseline)
Appendix G prescribes a specific system type per building type + climate zone:
| Building type | Baseline system (CZ 2A India) |
|---|---|
| Office < 6,500 m² | System 5 — Packaged VAV with electric reheat |
| Office > 6,500 m² | System 7 — VAV with HW reheat |
| Hotel | System 5 |
| Retail | System 6 — VAV with parallel fan-powered terminal |
| Hospital | System 7 |
| Healthcare clinic | System 5 |
Note: ASHRAE 90.1 baseline does NOT use chilled-beam, DOAS, free cooling, or other advanced strategies. The proposed-case can use them — that’s where credit comes from.
Step 3: Baseline equipment efficiency
Set baseline to ASHRAE 90.1 Table 6.8.1 minimums:
| Equipment | Baseline efficiency |
|---|---|
| Chiller water-cooled centrifugal > 528 kW | IPLV ≥ 6.30 |
| Chiller air-cooled centrifugal > 528 kW | IPLV ≥ 11.5 EER |
| Pump motors > 5.5 kW | IE3 |
| Fan motors > 5.5 kW | IE3 |
| LED lighting | Per Table 9.5.1 LPD limits (~7.5 W/m² office) |
The proposed-case typically uses 5-star equivalent (15-25% better than baseline).
Step 4: Building envelope (baseline)
Per ASHRAE 90.1 Table 5.5 by climate zone:
- Wall U-value: 0.7-0.9 W/m²K typical CZ 1A
- Roof U-value: 0.19-0.25 W/m²K
- Window U-value: 4-6 W/m²K
- Window-to-Wall Ratio: 40% maximum
Indian projects often have higher WWR (60% per ECBC); proposed-case captures the larger glass + better thermal performance.
Step 5: Occupancy + schedules
Same in both baseline + proposed. Realistic Indian commercial:
- Office: M-F 8:00-19:00 occupied at 60% average; weekend 5%
- Hotel: 24/7 with occupancy 70% average
- Retail: M-Sun 10:00-22:00 at 45% average
ASHRAE 90.1 has default schedules; Indian projects can use those or substitute realistic Indian occupancy. Use whichever the AHJ accepts.
Step 6: Outdoor air
Baseline + proposed both must comply with ASHRAE 62.1. For Indian projects: NBC 2016 Pt 8 ACH minimums govern (typically higher than ASHRAE 62.1). Use NBC values in both models.
Step 7: Run baseline + proposed
Run both simulations through annual hourly energy calculation. Tools: HAP, eQUEST, EnergyPlus + OpenStudio.
Output:
- Annual energy use breakdown (cooling, heating, fans, pumps, lighting, plug)
- Peak demand
- Energy cost (using project-specific tariff)
- Energy savings = (Baseline – Proposed) / Baseline
Step 8: Document + submit
LEED submission requires:
- Full simulation report with both models documented
- Energy savings table by end-use
- Annual cost savings (using project tariff)
- Equipment + system comparison table
Typical Indian commercial energy savings vs Appendix G baseline:
- Standard design: 5-15% savings (LEED EAp2 minimum)
- Good design: 25-35% (LEED EAc1 = 6-8 points)
- Premium design: 40-50% (LEED EAc1 = 10-14 points)
- Net-zero ready: 60%+ (LEED EAc1 = 14+ points)
Worked example: 10,000 m² Mumbai office
Climate Zone: 1A (ASHRAE)
Baseline system: System 5 packaged VAV with electric reheat
Baseline annual energy: 2,800 MWh = 280 kWh/m²/yr
Proposed-case strategies:
- DOAS + chilled beam (System type override): -25%
- ERV: -8%
- Free cooling waterside economiser: -5% (Mumbai limited)
- DCV: -8%
- LED + DALI: -10%
- VFDs: -5%
- Combined (with diminishing returns): ~38%
Proposed-case annual energy: 1,750 MWh = 175 kWh/m²/yr
Savings: 38% = LEED EAc1 = 8 points (above 36% threshold)
Capex premium: ~₹2-3 crore vs baseline = ~₹250-300/m²
Opex saving: ~₹1-1.5 crore/year
Payback: 2-3 years
Common Appendix G modeling mistakes
1. Different schedules in baseline vs proposed. The two models must use identical schedules; differences compromise comparability.
2. Baseline modeled with proposed-case enhancements. Forgetting that baseline doesn’t have DOAS, free cooling, etc.
3. Proposed-case at unrealistic 100% efficiency. Specify realistic equipment performance, not best-in-catalogue.
4. Ignoring infiltration in baseline. Baseline has 0.4 cfm/sf at 75 Pa; proposed often misses this assumption.
5. No envelope upgrade modeled. Indian projects with 50%+ WWR get bigger savings vs 40% WWR baseline; capture this.
Quick checklist
- [ ] Climate zone correctly identified per ASHRAE 169
- [ ] Baseline system type per building type table
- [ ] Baseline equipment minima per Table 6.8.1
- [ ] Baseline envelope per Table 5.5 climate zone
- [ ] Both models same occupancy + schedules
- [ ] Both models comply with ASHRAE 62.1 / NBC 2016 OA
- [ ] Energy savings ≥ 5% (LEED EAp2 minimum)
- [ ] Documentation per LEED EAc1 submission
References: ASHRAE 90.1-2022 Appendix G; LEED v4.1 BD+C EAc1; IGBC v3 EE-1; ASHRAE 169:2020 Climate Data; ECBC 2017 (companion).
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