ASHRAE HBDP flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

Energy Use Intensity (EUI)

Annual site energy consumed per unit of gross conditioned floor area, expressed in kBtu/ft2-yr or kWh/m2-yr. It enables comparison of buildings of different sizes and is the primary whole-building energy benchmark.

Window-to-Wall Ratio

The ratio of total glazed area to gross exterior wall area on a facade. It governs the trade-off between daylight and views versus solar gain and envelope heat loss.

Solar Heat Gain Coefficient

The fraction of incident solar radiation admitted through glazing, both directly transmitted and absorbed then released inward. Lower SHGC reduces cooling loads; it is specified per orientation.

Thermal Bridge

A path of high-conductance material that bypasses insulation, such as a slab edge or balcony. It raises effective assembly U-factor and must be broken with continuous insulation or structural isolators.

Passive Design Load Reduction

Reducing heating, cooling, and lighting loads through massing, orientation, envelope, and glazing before sizing active systems. Lower loads shrink every downstream equipment and operating cost.

Daylight Autonomy

The percentage of occupied hours when a target illuminance is met by daylight alone. It is preferred over static daylight factor because it reflects hourly availability and orientation.

Envelope U-Factor

The overall heat transfer coefficient of an assembly, in W/m2-K or Btu/h-ft2-F. It is the reciprocal of R-value and drives conduction losses through walls, roofs, and windows.

Energy Balance Equation

A building energy model must close: envelope, infiltration, internal, solar, and HVAC gains and losses sum to zero over the simulation period. Imbalance signals a modeling error.

Degree-Day Method

An estimate of annual heating or cooling energy from the difference between a balance-point temperature and outdoor temperature, summed over the year. Useful for screening, not design decisions.

NMBE Calibration Criterion

Normalized mean bias error, the average difference between modeled and measured energy normalized by measured data. Guideline 14 accepts about ±5% for monthly calibration data.

CV(RMSE)

Coefficient of variation of the root mean square error, measuring model scatter relative to measured mean. Guideline 14 accepts about ±15% for monthly data.

Parametric Sensitivity Analysis

Systematically varying design measures to rank annual energy savings per unit cost. Interactive effects mean savings from combined measures are not simply additive.

Bin Method

An energy estimate that bins hours by outdoor temperature and computes load at each bin. It approximates hourly simulation and is useful for economizer and part-load screening.

Demand Charge

A utility charge based on peak power (kW) during a billing period. A measure that cuts annual kWh can raise cost if it shifts load into on-peak hours.

Weather Normalization

Adjusting modeled or measured energy to a common weather year so that baseline and proposed cases, or different years, are compared on equal footing.

Ventilation Rate Procedure

ASHRAE 62.1 method setting outdoor air as per-person rate times occupants plus per-area rate times floor area, adjusted by zone air distribution effectiveness.

CO2 Demand-Controlled Ventilation

Modulating outdoor air based on measured indoor CO2, which tracks occupancy. It trims ventilation when occupancy is low but must not drop below code minimum rates.

Operative Temperature

The average of air temperature and mean radiant temperature, weighted by air speed. It is the temperature occupants actually experience and the basis of ASHRAE 55 comfort evaluation.

PMV and PPD

Predicted mean vote and predicted percentage dissatisfied. PMV estimates thermal sensation on a seven-point scale; PPD gives the fraction likely dissatisfied, with 80% acceptability a common target.

Daylight Glare Probability

A metric estimating the fraction of occupants disturbed by glare from windows. Values above roughly 0.35 to 0.40 indicate perceptible glare and warrant shading or light-redirecting design.

MERV Rating

Minimum Efficiency Reporting Value, a filter efficiency scale. MERV 13 and higher capture fine particulates, improving indoor air quality at a fan energy cost that must be balanced.

Source Control vs Dilution

Reducing pollutant emissions at the source, such as low-VOC materials and sealing, is more energy-efficient than diluting pollutants with additional outdoor air.

Reverberation Time

The time for sound to decay 60 dB in a room. Long reverberation impairs speech privacy and comfort; it is addressed alongside HVAC background noise in acoustic design.

Owner's Project Requirements

A written document stating the owner's functional needs, performance targets, and constraints. It anchors commissioning and is compared against the basis of design.

Basis of Design

The designer's record of assumptions, codes, and calculations that satisfy the owner's project requirements. Commissioning verifies that the installed systems match it.

Functional Performance Testing

Commissioning tests that verify systems under part-load, full-load, and failure modes. Testing only full-load operation misses most faults that occur in real operation.

Retrocommissioning

Applying the commissioning process to an existing building. It typically yields savings from correcting schedules, setpoints, and control sequences at low or no capital cost.

Monitoring-Based Commissioning

Using trend data and fault detection to continuously identify operational faults such as simultaneous heating and cooling, stuck valves, and schedule overrides after initial commissioning.

IPMVP Options

A framework for measurement and verification of savings. Options A through D differ in whether savings are measured at the whole-building or component level and how much is stipulated.

Sequence of Operations

The control document describing how equipment responds to conditions. Commissioning verifies it, and missing or unclear sequences are a leading cause of persistent energy waste.

Cycles of Concentration

The ratio of dissolved solids in cooling tower water to makeup water. Higher cycles reduce blowdown and makeup water but raise scaling risk and treatment requirements.

Embodied Carbon

Greenhouse gas emissions associated with material extraction, manufacture, transport, and disposal, expressed as kgCO2e. It is computed as material quantity times carbon factor.

Cradle-to-Gate Boundary

Life-cycle assessment stages A1 through A3, covering raw material extraction, transport, and manufacture up to the factory gate. It excludes construction, use, and end-of-life stages.

Construction Waste Diversion

The mass or volume of construction waste diverted from landfill divided by total waste generated. It is tracked during construction rather than estimated afterward.