High-Performance Building Design
Integrated design and load reduction
High-performance design starts by reducing loads before sizing systems: orientation and massing, envelope performance (U-factor, SHGC, air leakage), daylighting, and internal-load control. Understand the load order of operations: climate analysis → form and envelope → passive strategies → efficient systems → renewables. Questions often reward the earliest, cheapest intervention.
Metrics you must know
- EUI (energy use intensity, kBtu/ft²·yr or kWh/m²·yr), site vs. source energy.
- LPD (lighting power density), W/ft² for plug loads.
- SHGC vs. VLT and the daylight autonomy / sDA and ASE metrics.
- Peak demand versus annual consumption: a design can be efficient annually yet have a high peak.
Traps
- Confusing site and source energy (source multiplies by site-to-source factors).
- Assuming a low SHGC always helps - in heating-dominated climates with high internal gains it may increase heating energy, though cooling and peak usually dominate commercial loads.
- Treating passive survivability or resilience as equal to code compliance.
- Ignoring plug and process loads, which often exceed regulated loads in high-performance buildings.
- Confusing net-zero energy (annual site balance) with net-zero carbon (emissions balance).
Worked example / rule of thumb
A 100,000 ft² office targets 35 kBtu/ft²·yr site EUI. Baseline is 60. Savings needed = 25 kBtu/ft²·yr × 100,000 = 2.5 million kBtu/yr. If envelope plus lighting measures deliver 40% and HVAC 25% of baseline savings, you have 60 × 0.65 = 39 kBtu/ft²·yr - short of target; add plug-load and renewable measures. Rule of thumb: reduce loads first, then right-size equipment, then add renewables; every kBtu avoided at the load is cheaper than one supplied.