# Presentation: 676821

## Performance Metrics Data Model

- Robert J. Hitchcock, Ph.D.
- Building Technologies Department
- Lawrence Berkeley National Laboratory

- This work is supported by the California Energy Commission and the U.S. Environmental Protection Agency

## Overview

- Performance Objectives and Metrics
- Terminology and Concepts
- Examples
- Performance Metric Data Model
- Building Data Model with Performance Model
- Performance Metric Tracking Scenario

## Performance Metric Terminology

- Performance Objectives
- Qualitative statements regarding desired performance
- energy-efficiency; environmental impact; life-cycle economics; occupant health, comfort and productivity; and building functionality, adaptability, durability, and sustainability
- Performance Metrics
- Quantitative criteria in a structured format that provides value across the life cycle
- Critical variables that measure or influence an objective
- Capable of prediction or measurement at various stages of the project to evaluate the achievement of each objective
- Both Benchmark and Assessment values defined over time

**Notes:**
Performance Objectives are high-level qualitative expressions of desired building performance.  “I want the building to be energy-efficient”, “I want the building to provide occupant comfort.”  These type of statements are important, particularly at the early stages of project planning.  But they will not serve our overall purpose.
The concept then is to hierarchically delineate each Performance Objective, using quantitative criteria useful in evaluating alternative design or retrofit solutions, commissioning the newly constructed building systems, and tracking and maintaining the actual performance of the occupied building over time.
Thus, performance metrics are designed to explicitly represent project objectives, using quantitative criteria, in a dynamic, structured format that provides value across the life cycle.
A guiding principle in defining a performance metric is to identify a critical variable that measures, reflects, or influences a particular performance objective.
To be useful across the building project life cycle, each metric must also be capable of being either predicted or measured at various stages of the project so that the achievement of each objective can be evaluated.
Also, PMs can take on a number of different values over time, including Benchmark values that define desired/expected performance, and Assessment values that measure actual performance (predicted for proposed designs or measured for operating buildings).

## Cost Performance Metric Branch

**Notes:**
The data model that has been developed for performance metrics hierarchically organizes multiple metrics in a flexible structure.  Here is one possible breakdown, or branch, for a set of metrics associated with an objective on minimizing the overall life-cycle cost of a building, showing delineation of First Costs and O&M Costs.

## Energy and Comfort Metrics

**Notes:**
Here are two other hypothetical performance metric branches for Energy Use and Occupant Comfort.
Note some features of these examples:
LCC was a simple sum of its constituent PMs.  EUI and Occupant Comfort are not.
EUI includes important assumptions (e.g., lighting EUI -> W/ft2, ft2, hours).
Comfort has multiple PO levels (thermal, visual, air quality).
I also want to note that each PM is not necessarily a single value.  Chiller efficiency could be a COP, IPLV, 2D or 3D part load curve.  Lighting Operation could be total hrs/yr or an hourly profile or schedule.  Illumination could be min, avg, acceptable range, or spatial distribution.
Furthermore, over time each PM will have multiple values associated with it.  Always at least one benchmark value that identifies expected performance.  And over time, a history of predicted or measured values archiving the assessed performance of a proposed design or an occupied building.

## Performance Metric Data Model

- Performance Objective
- Name, Specifier,
- Date of Creation,
- Description
- Performance Metric
- Name, Specifier,
- Date of Creation,
- Description,
- Metric Type,
- Data Type,
- Source
- Data Values

**Notes:**
Jim Forester and I have actually gone to a lot of trouble to define an object-oriented data model for Performance Objectives and Performance Metrics that is included in the Industry Foundation Classes (IFC) standard developed by the International Alliance for Interoperability (IAI).  But, I am going to discuss only a simplification of that model here.
In OO terminology, we have an object class named Performance Objective, with attributes that record the Name of a PO (e.g., LCC), its Specifier (e.g., Owner), its Date of Creation, and a verbal Description (e.g., minimize LCC).
A hierarchical set of POs can be defined, and modified over time, for a specific building project.
And for each of these POs, a set of PMs can be archived to show a quantitative history of both expected and actual performance of the building, with respect to each of the objectives, over time.
A PM object class has attributes that record its Name, Specifier, Date of Creation, verbal Description, and Metric Type (i.e., Benchmark or Assessment), Data Type (e.g., Scalar, Time Series, 2D XY, 3D XYZ), Source (e.g., simulation prediction or in situ measurement), and its data values.
An example hierarchy for a specific building is shown at the right.  This snippet shows a LCC PO breakdown, with both benchmark and assessment PMs under First Cost and Energy Cost.

## Building Data Modelwith Performance Model

**Notes:**
Ideally, such a performance model would not stand alone, but would be archived along with a complete description of the building that had been designed and constructed to meet this performance.
This diagram shows the Performance Model on the left, a so-called Product Model of the building components and systems on the right, and a set of relationships between the performance objectives (e.g., cooling energy cost) and the building components (e.g., its chillers) that were selected in the attempt to achieve the performance objective.

## Performance Metric Tracking Scenario

**Performance Metric Tracking Scenario**

**Notes:**
And finally ,we get to the use of such a performance model to better assure the desired performance of a building during its operation.