ASHRAE HBDP cheat sheet

Whole-building energy use intensity (EUI) = annual site energy (kBtu or kWh) divided by gross conditioned floor area; compare against a climate-specific baseline, not a single national number.

Passive design order of operations: reduce loads (massing, orientation, envelope, glazing ratio) before sizing or selecting active systems; load reduction lowers every downstream capital and operating cost.

Window-to-wall ratio (WWR) drives cooling and lighting trade-offs: raising WWR increases solar gain and perimeter cooling but can cut lighting energy; optimum is climate- and orientation-dependent.

Orientation rule: long axis east-west minimizes west-facing glazing, which receives low-angle afternoon sun that is hardest to shade with overhangs.

Overhang effectiveness depends on latitude and window height; a horizontal projection blocks high summer sun but admits low winter sun only if the projection depth is tuned to solar altitude angles.

Envelope metric: assembly U-factor (W/m2-K or Btu/h-ft2-F) governs conduction; SHGC governs solar heat gain; both must be specified per orientation for high-performance envelopes.

Daylight autonomy and useful daylight illuminance (UDI) are preferred over simple daylight factor for design decisions because they capture hourly availability and glare risk.

Thermal bridging at slab edges, balconies, and shelf angles can dominate envelope heat loss; continuous insulation and thermal breaks are required to meet low U-factors.

Whole-building energy balance: Q_total = Q_envelope + Q_infiltration + Q_internal + Q_solar + Q_HVAC; each term must close to zero over an annual simulation for a valid model.

Degree-day estimate: annual heating energy ≈ (UA + infiltration UA) × HDD × 24 / efficiency; useful for screening, not for design decisions.

Model calibration target: ASHRAE Guideline 14 accepts normalized mean bias error (NMBE) within ±5% and coefficient of variation of RMSE (CV(RMSE)) within ±15% for monthly data.

Baseline vs. proposed comparison must hold weather, schedules, internal loads, and utility rates constant; only design measures change between runs.

Parametric sensitivity: rank measures by annual energy savings per unit first cost, then check interactive effects-savings from combined measures are not additive.

Free cooling / economizer hours depend on climate bin data and changeover setpoint; bin method approximates hourly simulation for early-stage screening.

Peak demand drives utility cost under demand charges; a measure that cuts annual kWh can raise peak kW if it shifts load to on-peak hours.

Uncertainty: Monte Carlo or scenario analysis on weather, occupancy, and plug loads communicates model risk better than a single deterministic EUI value.

Ventilation rate procedure: outdoor air per person (Rp) plus per floor area (Ra); design OA = Rp × occupants + Ra × area, adjusted by zone air distribution effectiveness.

CO2-based demand-controlled ventilation uses steady-state mass balance: indoor CO2 ≈ outdoor CO2 + (generation rate)/(outdoor air rate); use it to trim OA when occupancy is low, not to justify below-minimum rates.

Thermal comfort (ASHRAE 55) is defined by operative temperature, humidity, air speed, metabolic rate, and clothing; PMV/PPD predicts dissatisfaction, and 80% acceptability is the common design target.

Glare control: daylight glare probability (DGP) above roughly 0.35–0.40 indicates perceptible glare; automated shading and light shelves reduce it without sacrificing daylight.

Acoustic design: background noise from HVAC (NC/RC ratings) and reverberation time in occupied rooms both affect speech privacy and perceived comfort; address them at the same time as ventilation design.

Filtration and ventilation together control indoor pollutants; MERV 13+ filters reduce particulates, but source control (low-VOC materials, sealing) is more energy-efficient than dilution.

Moisture control: keep interior dew point below surfaces to avoid condensation; vapor retarder placement depends on climate zone and assembly orientation.

Commissioning process: pre-design, design, construction, acceptance, and post-occupancy phases; each phase has documented owner's project requirements (OPR) and basis of design (BOD).

Functional performance testing verifies systems under part-load, full-load, and failure modes; a test that only confirms full-load operation misses most real-world faults.

Retrocommissioning targets existing buildings: investigate, prioritize no/low-cost fixes, then implement and verify; typical savings come from schedule and setpoint corrections.

Monitoring-based commissioning uses trend data and fault detection (FDD) to catch simultaneous heating and cooling, stuck valves, and schedule overrides continuously.

Measurement and verification follows IPMVP options (A–D); option selection depends on whether savings are measured at the whole-building or component level.

Sequence of operations is the control document that commissioning verifies; unclear or missing sequences are a leading cause of persistent energy waste.

Seasonal and post-occupancy recommissioning is required because occupancy, tenant fit-outs, and control overrides degrade performance over time.

Indoor water savings are measured against a baseline of fixture flow rates and flush volumes; high-efficiency fixtures cut both potable demand and wastewater volume.

Net zero water hierarchy: reduce demand, then reuse (rainwater, greywater, condensate), then treat and recharge; capture potential depends on rainfall and roof area.

Cooling tower water use: cycles of concentration (CoC) set blowdown; higher CoC cuts makeup water but raises scaling risk and requires appropriate treatment.

Embodied carbon = material quantity × carbon factor (kgCO2e per unit); compare assemblies on a whole-building life-cycle basis, not single materials in isolation.

Life-cycle assessment stages: cradle-to-gate (A1–A3) covers extraction and manufacture; cradle-to-grave adds construction, use, and end-of-life (A4–C4).

Material selection rules: prioritize reused and recycled content, low-VOC and low-toxicity finishes, and locally sourced or rapidly renewable materials where performance is equal.

Construction waste diversion is measured as diverted mass or volume divided by total waste generated; track it during construction, not after.