Air Handling Unit (AHU):
A system that mixes outdoor air and zone return air (up to 100% of either), conditions it using heating and/or cooling coils, and uses supply and/or return fans to force the air into building zones. Packaged systems that do the same thing might go by other names (e.g. rooftop unit), but for the purposes of BRS, can be modeled using the AHU section.
Airflow
Volumetric flow rate of air in a duct with units of cubic feet per minute (cfm)
Baseline
The building and its operations prior to any intervention (e.g. Re-tuning, performance contracts, retrofits, etc)
Building Automation System (BAS)
An interlinked network of software and hardware to monitor and control a building's mechanical and electrical systems, including heating, ventilation and air-conditioning (HVAC), lighting, security and fire systems.
Building Pressure
The static pressure of building air relative to ambient outdoor air. Note that building pressure can vary from floor to floor in significant ways for tall buildings during hot and cold weather. This is called the stack effect. The BRS calculates only a single building pressure.
Building Re-tuning
An interlinked network of software and hardware to monitor and control a building's mechanical and electrical systems, including heating, ventilation and air-conditioning (HVAC), lighting, security and fire systems.
Calibration
For energy models, calibration is the process of making modifications to the original baseline building specifications to produce simulated energy consumption that more closely matches metered energy consumption. The modifications are typically made to building and HVAC system parameters that are hard or impossible to determine from an audit or otherwise have higher uncertainty associated with them.
Constant Speed
A piece of equipment that is only capable of producing a fixed output flow rate. This most commonly may apply to a pump, fan, chiller, or cooling tower.
Cooling plant
The set of mechanical components and systems responsible for generating a centralized cooling supply (usually chilled water) for a building. The components typically include primary and secondary pumps, chillers or district cooling heat exchangers, cooling towers or dry coolers, valves, connecting piping, and water treatment systems.
Dashboard
For digital media, A single page that either conveys all of the most useful and salient information about a system or process using graphics and performance metrics. For the BRS, the re-tuning dashboard shows all of the baseline control strategies for each of the re-tuning measures, while also allowing the user to make modifications to those controls and initiate a new simulation to investigate the impact of those modifications
Dedicated Outdoor Air System (DOAS)
An air-handler section that conditions 100% outside air prior to either delivering this conditioned outdoor air directly to building spaces or in some cases, to the outdoor air mixing box of a conventional air-handler. A dedicated outdoor air system often, but not always includes an energy recovery system. The energy recovery system may include either a heat recovery wheel to transfer heat between an outdoor air stream and an exhaust air stream, or a set of coils (one in the outdoor air stream and one in the exhaust air stream) and a pumping system between them. This is referred to as a run-around loop.
Demand Control Ventilation
A control strategy that adjusts the minimum outdoor airflow rate or minimum airflow damper command based on the CO2 concentration in building zones, or in the return air from the air-handler.
Density (peak loading)
The installed or peak power consumption for lights, electric equipment, or the number of people, in each case normalized by the floor area served [W/ft2] or [People/ft2].
Differential Pressure
The difference between the pressure measured at two points in either a chilled water or hot water loop, usually the difference in pressure between the outlet of the pumping system and the farthest point in the loop. The differential pressure provides a measure of how much (as a minimum) water pressure will be available to each of the building’s coils.
Efficiency
For a component or system, the ratio of useful output energy to the required input energy.
ENERGY STAR Portfolio Manager Score
A standard for benchmarking commercial buildings comparing energy performance to comparable buildings, normalized for climate zone and operating characteristics. A score of 50 represents median performance. A higher score is better than average; lower is worse. See
https://www.energystar.gov/buildings/benchmark?s=mega
Energy Use Intensity (EUI)
An area normalized metric of a building’s energy use per year. A low EUI generally signifies an energy efficient building, however good energy performance. However, certain occupancies use more energy than by nature of the operations (e.g. hospital vs warehouse).
Heating plant
The set of mechanical components and systems responsible for generating a centralized heating supply (either hot water or low-pressure steam) for a building. The components typically include primary and (sometimes) secondary pumps, boilers or district steam heat exchangers, valves, connecting piping, water treatment systems and steam condensate return.
Infiltration
The transfer of outdoor air across the building envelope and into the building through cracks and intentional openings
Interval metered data
A dedicated building meter that collects utility energy consumption at an hourly or sub-hourly interval.
Model (building energy)
A simplified representation of a building that can be used to estimate/predict performance and energy consumption for unknown conditions (e.g. system upgrades and control changes). Models are usually most useful in estimating the difference between a baseline and a post-intervention state than in predicting the energy consumption for a new building with unknown consumption
Monthly billing data
Metered energy consumption data from the utility provider that is provided for the purposes of monthly billing. In the cases of some campuses of buildings, this data may be collected at the campus level and thus not of much use for calibrating building energy models.
Optimal Start
A machine learning algorithm that provides an air-handler with a custom start-up time every morning in response to the outdoor air temperatures, zone temperatures, and time remaining prior to occupancy.
Primary Loop/Primary Pump
In common building parlance, the primary loop is a water loop that pumps water through the chillers or boilers. It may also be the same loop that serves the building hot water or chilled water coils. In the BRS, the term primary is used only to refer to a set of pumps that are constant speed, serving the boiler or chiller, when there is another set of pumps that serve the rest of the building (secondary loop). In the event of single-loop systems, these should be modeled in the BRS as secondary loop-only systems.
Schedule
This could refer to an actual schedule used for control or building operations, such as an HVAC occupancy schedule, or a building occupancy schedule or it could refer to an operational time-of-use profile that is applied to internal loads (lighting, equipment and people) to help the model estimate how these loads vary as a function of time of day and day type.
Secondary Loop/Secondary Pump
In common building parlance, the secondary loop is a water loop that pumps water through the building heating or cooling coils and back, and interfaces with a separate primary loop through a decoupler bridge, allowing the two loops to have different flow rates. In the BRS, the term secondary is used only to refer the loop serving the building heating or cooling loads, regardless of whether this loop also flows through the chillers or not.
Solar Heat Gain Coefficient (SHGC)
the fraction of solar radiation transmitted or absorbed through a window and subsequently released as heat inside the zone.
Static Pressure (SP)/Static Pressure Reset
The pressure downstream of the supply fan, typically measures 2/3 of the way down the duct, with respect to the zone (building pressure)
Supply Air Temperature (SAT)/ Discharge Air Temperature (DAT)
The temperature at the outlet of the AHU and the inlet to zone air terminal units
Simulation
The exercising of a model to produce a prediction – in this case about annual energy consumption and CO2 emissions.
Thermal Mass
Building construction layers, equipment and furnishings that create thermal inertia. This is reflected numerically as the amount of heat that must be provided to produce a unit change in zone temperature.
U-Factor
A measure of how much thermal heat (excluding solar transmittance, in the case of windows) is transmitted through a wall or window, as a function of the temperature difference on each side. The U-factor is the inverse of the effective R-Value, so can be roughly estimated by taking the inverse of the insulation R-Value, however this does not take into account thermal breaks and additional thermal resistance provided by other layers of wall construction, including air gaps.
Variable Speed
An HVAC component that is capable of adjusting its speed through the use of a variable speed drive to provide a range of flow rates. This designation may apply to pumps, fans, chillers, and cooling towers.
Weather data, TMY (Typical Meteorological Year)
a collation of selected weather data for a specific location, including hourly values of solar radiation, outdoor air temperature and humidity for a one-year period. The full data set includes other weather-related values and measurements that are not used by the BRS. The values are generated from a data bank much longer than a year in duration, at least 12 years. It is specially selected so that it presents the range of weather phenomena for the location in question, while still giving annual averages that are consistent with the long-term averages for the location in question. TMY3 weather data is used in the BRS, with 1,020 U.S. locations and terrirories that are available for selection by the user.
Zone
A thermal zone in a building is an area of a building served by a single thermostat and a piece of or set of equipment controlled by that thermostat. It may include a single room, several rooms, or only a fraction of a larger open space. For modeling purposes, the ‘zone’ may be much larger, encompassing several thermal zones in the actual building. The goal of the modeler is to group several thermal zones with similar loads and characteristics into a single modeled zone for simplicity.