R-Zero - Measurement and Verification Plan
Executive Summary
Section titled “Executive Summary”This document describes the measurement and verification (M&V) methodology and the data intake requirements for occupancy-driven control of ventilation (ODCV) managed by R-Zero. An ODCV system reduces outdoor-air intake toward the ventilation floor when a space is lightly occupied. The mechanical system then tempers less fresh air, and in a variable-air-volume (VAV) building the fans also move less air. The avoided energy is the measure of impact.
The plan covers the counterfactual, the metering infrastructure, the data collection protocols, and the savings calculations.
Evidence of Asset
Section titled “Evidence of Asset”R-Zero provides evidence that demonstrates the installation of the measure:
- The building management system (BMS) point dictionary that names each controlled box or air handler
- The control sequence of operation, with the ventilation floor and the standby setpoints
- The commissioning report that establishes the pre-ODCV outdoor airflow
Methodology Selection
Section titled “Methodology Selection”A deployment takes one of two shapes, and each shape has its own methodology. The shape depends on what the BMS trends, not on a preference.
| Deployment | Methodology | Measured signal | Savings components |
|---|---|---|---|
| VAV boxes with an occupancy standby signal | Ventilation Optimization | Hourly standby fraction across the controlled boxes | Conditioning and fan |
| Air handler with a metered outdoor-air damper | Ventilation Reduction (ODCV) | Hourly outdoor airflow at the damper, in CFM | Conditioning |
Both methodologies temper the outdoor air with the standard psychrometric equation. The sensible term uses 1.098 BTU/h per CFM per °F. This factor comes from the specific heat of moist air at normal building conditions, which is the air that an air handler moves.
One asset takes one of the two. The BMS trend decides which: a VAV deployment reports the per-box standby state, and an air-handler deployment meters the airflow at the damper.
Data Requirements
Section titled “Data Requirements”Incorporated Data Requirements
Section titled “Incorporated Data Requirements”The following are defined in the Shared Guidelines methodology:
- Definitions
- Electricity Carbon Intensity Calculations
- Shared Data Intake Requirements
- Consequential Carbon Accounting Rules
- EAC Definition and Rules
- Generated Versus Avoided Emissions
Attributional Data
Section titled “Attributional Data”The Shared Guidelines methodology lists the data that every asset provides. The following data is required in addition to that data. Every field is a parameter on the asset, and an operator can change it after registration.
| Field | Description | Default if not provided | Required? |
|---|---|---|---|
| Building type | Classification of the building according to the NREL ComStock categories | Y | |
| Conditioning + fan share of HVAC | Fixed share for the HVAC savings percentage, when the controlled rooms are a different use than the building | ComStock, or a stated 70% | |
| Commenced operation date | Date when ODCV control began operation | Y | |
| Design supply CFM, per floor | Air handler supply-fan design airflow, from the mechanical drawings | 26,800 | Y |
| Design return CFM, per floor | Air handler return-fan design airflow, from the mechanical drawings | 35,500 | Y |
| Fan power per CFM | Fan power-to-airflow ratio at design, in W/CFM | 0.6 | |
| Fan affinity exponent | Exponent that turns an airflow cut into a power cut | 2.5 | |
| Floors with identical controls | Number of floors that the design airflows scale to | 5 | |
| Controlled area fraction | Controlled footprint divided by the whole-building footprint | 0.0476 | Y |
| Standby flow reduction | Airflow that one box sheds at full standby | 0.75 | |
| Outdoor-air fraction | Share of design supply air that is outdoor air | 0.20 | |
| Counterfactual outdoor airflow | Pre-ODCV outdoor airflow in CFM, for the air-handler deployment | 5,400 | Y |
| Cooling COP | Chiller efficiency, applied to every cooling hour | 4.0 | |
| Heating efficiency | Divides the tempering load to give the energy the site buys, in every heating hour | 0.85 | |
| Heating energy source | Fuel that carries the heating savings and selects its emission factor | Hot water | |
| Humidification active | Set this field to 1 when the air handler humidifies in winter | 0 | |
| Return-air temperature default | Value for an hour when the BMS does not trend return-air temperature | 72 °F | |
| Return-air humidity default | Value for an hour when the BMS does not trend return-air humidity | 45% | |
| Air handler mode map | Flags for each BMS mode code: heat, cool, economizer, idle, fault | A 10-mode default map |
The geometry defaults describe the first pilot site. Set them from the building’s own drawings.
The heating efficiency converts the tempering load into purchased energy: purchased energy = load ÷ η. A site that buys district hot water or steam carries the value from its own workbook, and the pilot site uses 0.85. Its savings were reconciled against that value.
Timeseries Data
Section titled “Timeseries Data”R-Zero delivers the BMS trend as a change-of-value export, with a point dictionary. The platform aggregates the export to hourly values. The channels are:
| Channel | Description | Required |
|---|---|---|
| Standby status, per box | Binary occupancy state of one VAV box. 1 is standby, and 0 is active | Y for a VAV deployment |
| Outdoor airflow | Measured outdoor airflow at the damper, in CFM | Y for an air-handler deployment |
| Air handler mode code | Integer operating mode, matched against the mode map | |
| Outdoor-air temperature | Outdoor dry-bulb temperature, in °F | |
| Outdoor-air humidity | Outdoor relative humidity, as a percent | |
| Return-air temperature | Return-air temperature, in °F | |
| Return-air humidity | Return-air relative humidity, as a percent |
The measurement uses the hours that carry the required channels of the deployment. The log reports how many hours it dropped, and which input was missing.
The HVAC Share of the Savings
Section titled “The HVAC Share of the Savings”The savings are metered against the loads that the controls touch. A buyer also asks what share of the building’s HVAC energy the savings represent. Two ratios answer that question, and neither one is metered at the site:
- The share of building electricity that HVAC spends
- The share of HVAC that the controlled end uses spend, which is cooling and fans for a VAV deployment and cooling alone for an air-handler deployment
The platform sources both ratios from NREL ComStock, for a representative building of the asset’s building type in the site’s climate zone, with a p25 to p75 uncertainty band.
ComStock describes the whole building. The share depends on the rooms that the project affects. If those rooms are a different use than the building around them, fix the share with a value from this table:
| Rooms under control | Conditioning + fans ÷ HVAC | Source |
|---|---|---|
| Commercial, average | 75% | CBECS 2018 |
| Office | 72% | CBECS 2018, ASHRAE 90.1 |
| Healthcare, hospital | 70% | CBECS 2018, ASHRAE 170 |
| Laboratory | 80% | ASHRAE 90.1 energy models |
An office wing inside a hospital is the common example. The wing spends its HVAC energy like an office, so the office row is the correct share for it. The hospital row describes the building around the wing.
A fixed share is a stated estimate. The ComStock figures beside it carry the uncertainty band, and the platform reports both so a reader can compare them. The ComStock ratio is over electric HVAC, and the table is over all fuels, so the two have different denominators. A district-heated building spends its heating energy on district heat, so its electric-HVAC ratio runs above the table.
For a laboratory site, select the nearest commercial building type. Then fix the share at the laboratory row.
Weather Scenarios
Section titled “Weather Scenarios”An air-handler deployment runs the same hours twice, on two weather sources:
- Platform weather, which is the reported scenario. Temperature and humidity come from the WattCarbon weather service.
- Sensor weather, which is the validation scenario. Temperature and humidity come from the BMS outdoor-air sensor, with NOAA data as backfill for the gaps.
The two scenarios give identical results when their weather inputs are identical. A difference measures the sensitivity of the savings to the weather source. The measurement log reports the total for each scenario, side by side.
A vendor calculation that reads the BMS sensor corresponds to the sensor-weather scenario. Compare a vendor workbook against that scenario. A difference larger than ±5% indicates sensor drift, a mismatched mode map, or a different efficiency assumption.
A VAV deployment reports one scenario, on platform weather.
Expected Outputs
Section titled “Expected Outputs”WattCarbon provides the savings through the dashboard and the API:
- Electricity savings in kWh, at hourly resolution
- Heating savings in the base unit of the heating source. District hot water is in MMBtu, gas is in therms, and steam is in Mlb
- CO₂e avoided, from time-matched grid carbon data for the site. Electricity is reported on both a marginal and an average basis
- The estimated HVAC savings percentage, with the ComStock band and the share that scaled it
- The savings read against three denominators, each labeled with the question it answers
Verification Protocols
Section titled “Verification Protocols”The platform runs these checks on every measurement, and reports each one in the measurement log:
- Mode-code coverage. For an asset that trends a BMS mode code, every code in the period must have an entry in the mode map. An unmapped code stops the measurement and names the code, so an operator can extend the map.
- Mode hours. An air-handler deployment tabulates the hours in each observed mode, with the gating outcome of each mode.
- Input coverage. The measurement reports how many of the period’s hours it measured, and how many it dropped for a missing input.
- Weather sensitivity. An air-handler deployment reports the savings from each weather source, side by side.
WattCarbon reviews these figures for each reporting period.