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Measuring Performance of Sustainable Buildings

by Joel Ann Todd, Environmental Consultant and Kim M. Fowler, Senior Research Engineer, Pacific Northwest National Laboratory

Last updated: 12-02-2009

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Introduction

There are now many resources available to support the design of more sustainable buildings and to assess the "green-ness" of these designs. As the field of sustainable design evolves, many in the field are thinking about measuring the actual benefits of these designs—the performance of buildings that we consider "green." Numerous projects in the U.S. and other countries are attempting to define the qualitative and/or quantitative measures of sustainability and the data needed to implement and assess these measures. These efforts are important because they will enable us to determine:

Building performance metrics

We will also be able to fine tune our sustainable design strategies as we learn what has the most impact and what is most cost-effective. See also WBDG Functional—Meet Performance Objectives.

The purpose of this Resource Page is to provide references for various aspects of performance measurement, and to enable users to learn about what is available in this evolving field. Users are encouraged to email the authors of this Resource Page at measuregreenbuildings@yahoo.com with additional resources so that the section can be kept up to date.

In addition to the WBDG Sustainable Branch, an excellent overview of the various benefits of sustainable design can be found in "Making the Case for Green Building" in Environmental Building News, April 2005. This article outlines the range of potential benefits that could be the subject of performance measurement studies: first cost savings, reduced operating costs, other economic benefits, health and productivity benefits, community benefits, environmental benefits, and social benefits.

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Description

Different users ask different questions about performance and want different information and levels of detail. High level measures provide a quick overall assessment of performance on most critical parameters and enable an organization to report on its overall environmental improvement and the benefits of its sustainable design activities. More detailed measures can explain unexpected results and enable a building manager to check on problem areas or monitor/tune ongoing performance of systems.

A. Challenges of Measuring Performance

Measuring performance is challenging for many reasons.

Conceptual Challenges

There are different concepts or definitions of "performance" and, as a result, we are often talking past one another. "Performance" can mean: Does the building, as built, exhibit characteristics that are green or sustainable? Is the building routinely operated and maintained sustainably? Are building upgrades, renovations, reconfigurations sustainable? What are the environmental results of sustainable strategies, in terms of resource consumption and environmental impacts? What are the savings realized from a sustainable building (and costs)? What are other benefits (and costs) of sustainable building (social, health, community, etc)?

Practical Challenges

Actual vs. Modeled Performance. For some metrics, it is relatively easy to obtain actual performance data. For others, it is more difficult and models or estimations must be used. If models are necessary, it is best to use any relevant available "actual" data when possible, to better reflect operating performance rather than design performance.

Data Availability. In some cases, data to support performance metrics is not available. For example, individual buildings on campuses or military installations may not be separately metered for energy or water use.

Feasibility/Effort Required to Gather Data. In some cases, it might be possible to gather data but it might require more effort or cost than an agency or organization is willing to expend. For example, an agency might not be willing to conduct a survey of users to gather data on commuting or satisfaction with aspects of the building.

Data Quality and Consistency. Even when measured data is available, the reliability of the information may be questionable and the ability to collect the information consistently over a given time period may be difficult. For example, metrics related to operations and maintenance may not be collected in a consistent manner over time depending on the sophistication and reliability of the tracking system being used.

Isolating Effects of Individual Buildings. For some aspects of performance, it is very difficult to determine the impact of a single building as opposed to a development or community. For example, we can measure changes in surface water quality, but then how can we attribute these changes to design and operational aspects of individual buildings?

Benchmarks for Comparison. For performance measurement to be useful, we need to be able to determine the level of performance and how it compares to a more typical building in the same climate, with the same occupancies. This requires the specification of benchmarks. Benchmarks can be a building's performance over time, to measure improvements that result from renovation or changes in operations, or it can be based on external yardsticks such as LEED®, EnergyStar®, or others.

B. Resources for Measuring Performance of Sustainable Buildings

In recent years, building owners and designers, researchers, and others have begun performing studies related to the costs and benefits of sustainable design. Some of these studies attempt to address the full impact of sustainable design, while others emphasize the economic aspects, the environmental impacts, and the social aspects separately. Other differences in the studies include whether or not the data is measured, modeled, or some combination of both, whether the information is based on a single building or multiple buildings and the differences in how the baseline or benchmark is being used.

Table 1 characterizes available studies on key parameters and can be used to identify studies that address questions of interest; brief summaries of these studies as well as links for further information follow the table.

Table 1: Available Studies on the Costs and Benefits of Sustainable Design

Table 1: Available Studies on the Costs and Benefits of Sustainable Design

Resources Focused on the Financial/Business Aspects of Performance: Making the Business Case

One of the most persistent questions about sustainable design is its cost - does it cost more to build and operate a green building and if so, how much more? How long does it take to recoup these costs in operating savings? Which investments in green design pay back more quickly? What other business benefits are there, such as productivity and user satisfaction?

Example of green office space.

Green office space.
Photo courtesy of Interface.

Cross-section of roof depicting heating and cooling systems

Resources Focused on the Environmental Aspects of Performance

Buildings affect all aspects of our environment—air, rivers and streams, soils, plants and animals, oceans—the visible and invisible network of life on the planet. Reducing the damage caused by buildings—and ultimately creating buildings that are net contributors—is an important goal of sustainable design. As noted under social, health, and community measures, it is often challenging to measure actual effects of a single building.

Most information currently available on building performance is contained in case studies that report on strategies incorporated in the design and some actual results, generally energy and water savings. The High Performance Buildings Database, described below, is one resource for such case studies.

One specific type of measurement is environmental life cycle assessment (LCA), a compilation and evaluation of the inputs, outputs, and the potential environmental impacts of a product system throughout its life cycle. This "cradle to cradle" (or cradle to grave) approach is often suggested as a framework for performance measurement that provides a broader, more comprehensive perspective instead of a focus on only one aspect of performance. LCA can address individual building products, assemblies or systems, or whole buildings. It is different from life-cycle costing (see Financial/Business Aspects of Performance section).

Standardized Metrics and Procedures for Building Energy Performance, Lighting System Performance, Photovoltaic System Performance, and Source Energy and Emissions from Energy Use in Buildings

Energy consumption in buildings can have the largest environmental impact of any aspect of the building. The energy performance of buildings can be defined in many ways, which can lead to different conclusions. The Performance Metrics Project (PMP) at the National Renewable Energy Laboratory (NREL) is a U.S. Department of Energy (DOE) commercial buildings research activity whose goal is to standardize the measurement and characterization of building energy performance. This project produced standard performance metrics and procedures for determining building energy performance, lighting system performance, PV system performance, and source energy and emissions from energy use in buildings. Another source of standard of building performance measures is ASHRAE Guideline 14, which presents a detailed description of procedures for measuring and reporting energy and demand savings geared toward retrofit applications.

In-Depth Case Studies of Energy Performance of Six High Performance Buildings by U.S. Department of Energy, National Renewable Energy Laboratory.

An example of comparison graphs available in the NREL studies

An example of comparison graphs available in the NREL studies

The National Renewable Energy Laboratory (NREL) conducted detailed studies of six buildings to document their actual performance and to understand the issues that affected the performance levels achieved. Post-occupancy evaluations began with extensive building monitoring for at least one year; energy flows established from the measured data were used to calibrate building models for energy simulations of performance. Summaries of this study and lessons learned can be found at:

The more detailed studies of each of the six buildings, including methods and metrics used, are available as follows:

Chesapeake Bay Foundation's Philip Merrill Environmental Center, Annapolis, MD

Chesapeake Bay Foundation's Philip Merrill Environmental Center, Annapolis, MD

Resources Focused on the Social, Health, and Community Aspects of Performance

This is the least studied and least understood aspect of building performance. In fact, we have not clearly defined the parameters to be included. It is often challenging to measure actual effects of a given building on social, community, and health indicators. Note that many of the studies included under Financial/Business Aspects of Performance also include parameters related to human health and well-being, which also relate to this category.

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Application

Using the Results of Performance Measurement

As noted in the Introduction, performance measurement can be used for a wide variety of purposes. Two examples follow. In the first example, an in-depth assessment of energy performance is used to improve the performance of the buildings studied and to understand how energy performance can be improved in future buildings. In the second example, metrics were developed and are being applied for a "whole building" performance evaluation of sustainably designed buildings.

To provide information needed to achieve this goal, the National Renewable Energy Laboratory (NREL) studied six buildings in detail to understand the issues related to the design, construction, and operation of the current generation of low-energy buildings. Post-occupancy evaluations began with extensive building monitoring for at least one year; energy flows established from the measured data were used to calibrate building models for energy simulation performance.

Although all of the buildings achieved energy savings, none of the buildings performed as well as expected. NREL's detailed analyses identified some of the reasons for the actual performance levels and enabled some of the buildings to take steps to improve their performance. In addition, the study led to a greater understanding of factors that affect our ability to achieve energy performance goals. For example, daylighting was less successful than anticipated and peak energy demands were greater, due to such factors as cloudy conditions during peak demand reducing PV effectiveness. Expectations for occupant behavior were optimistic. In one building, the energy consumption was considerably higher than models during the design process predicted. The study was able to determine the cause of the problem so that the owner could take appropriate remedial steps.

Some of the key conclusions of this exercise include the following:

To accomplish the goal of providing actual data on sustainably designed Navy facilities, the metrics developed through the FEMP Sustainable Building Cost and Performance Metrics project are being used on seven Navy building sets (see Table 2 for summary of metrics). Each building set includes one sustainably designed building and a similar building on the same Navy site designed in a more 'conventional' fashion. In addition to using the conventionally designed building for comparison, industry benchmarks and existing Navy data will be used when available. The building types that are included in the project are office buildings, barracks, and fitness centers.

Table 2: Building Cost and Performance Metrics for Navy Facilities

Table 2: Building Cost and Performance Metrics for Navy Facilities

Site and building characteristic data (e.g., size of building, number of occupants, etc.) were collected in order to normalize the performance data for analysis. Meters and data collection systems needed to be put in place for some of the buildings. The building cost and performance data will be collected for a minimum of 12 months. The data from these buildings will be used to calculate a return on investment for the sustainably designed facilities, to identify opportunities for individual building performance improvement, and to develop design guidance on the sustainable design techniques that appeared to be contributing the greatest to the buildings' performance.

To date the project has involved identifying the target buildings, identifying the current metering capability, and collecting site and building characteristics data. The first challenge for the project was identifying which sustainbly designed buildings in the Navy portfolio would be the best candidates. Having buildings that were occupied for more than 6 months and identifying a 'matching' conventionally designed building at the same site with the same function proved to be significant limiting factors. Once the buildings were selected the challenge was to clearly identify the metering needs, which have been greater than expected, and to gather the site and building characteristics for each building. Once the building meters are in place, the collection of monthly performance data will begin.

Questions about this project can be directed to:

Dennis O. Talton, R.A.
Special Assistant for Architecture and Accessibility
Sustainable Development Program Manager
Naval Facilities Engineering Command, Atlantic
Phone: 757-322-4211
Fax: 757-322-4416		 Kim M. Fowler
Senior Research Engineer
Pacific Northwest National Laboratory
PO Box 999 K6-10
Richland, WA 99352
Phone: 509-372-4233
Fax: 509-372-4370
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Additional Resources

WBDG

Building / Space Types

Applicable and relevant to all building types

Design Objectives

Cost-Effective, Functional / Operational, Historic Preservation, Productive, Secure / Safe, Sustainable

Products and Systems

Building Envelope Design Guide
Federal Green Construction Guide for Specifiers:

Project Management

Building Commissioning, Project Delivery Teams, Project Planning and Development, Project Delivery and Controls

Operations and Maintenance

Facilities Operations & Maintenance

Applied Research

Sustainable and High Performance Building Strategies Research:

Energy Efficiency Research:

Organizations

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Related Resource Pages
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WBDG Services Construction Criteria Base