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Building Operating Management

Building’s Energy Efficiency, Occupant Comfort Are Related



Research, new metrics show the often overlooked relationship between energy efficiency and occupant comfort helps to define a truly high-performance building. Part 1 of a 5-part article.


A truly high-performance building is one that is both energy efficient and occupant friendly. But it hasn't always been easy to marry those two measures. Often, they're treated independently. This shouldn't be the case, as an increasing body of research shows the two are very much related.

For instance, a study by the National Center for Energy Management and Building Technologies (NCEMBT) investigated this critical question: "Is there a relationship between a building's energy performance and the occupants' acceptance of the indoor environment?"

That study introduced a key concept called the "Acceptability Index Value" (AIV), or the ratio of the Energy Utilization Index (EUI) and measures of occupant acceptability (in percentage). The intent of this ratio is to evaluate the effectiveness of energy use to achieve a specified percentage of occupant acceptability. The study demonstrated that new metrics can be established that enable evaluation of the effectiveness of energy used to provide for acceptable occupant responses, occupant performance, and productivity within a building. These new metrics define objective measures that can be used to qualify buildings for further evaluation as "high-performance buildings."

But to answer the question of how energy efficiency is related to occupant comfort and satisfaction, it's important to start with the ultimate objectives of a building in the first place: First, to provide a safe, secure, and healthy environment for occupants, and also, to promote the occupants' well-being and performance.

To achieve these goals, energy must be expended on various building functions: electrical power, lighting, heating, cooling, moisture control, acoustics, and ingress and egress control. Since the 1970s, energy use has been in continuous focus by federal, state, and local policies, as well as private initiatives. The unifying goal has been to reduce energy consumption in all its forms.

Along with these policies, the definition of what a building should accomplish has changed to also incorporate "green," "sustainable," and "high performance." This shift has emphasized energy savings and reductions of raw materials with seemingly little consideration for the quality of the building environment and its impact on well-being, performance, and productivity. Now we are constructing and operating high-performance buildings where it is possible for occupants to be dissatisfied with the indoor environment, thus raising the question: Are these really high-performance buildings?

Answering that question means examining some of the common metrics used to define high performance.

Building Energy Measures

The most common measure of a building's energy performance in the United States is the Energy Utilization Index (EUI), which normalizes the annual building energy consumption over the gross floor area of the building. Typically the sum of all energies consumed by the building (electricity, natural gas, etc.) over a year is converted into a common dimension (e.g., Btu), which is then divided by gross floor area of the building (e.g., Btu/GSF yr).

Building energy performance metrics like EUI provide some meaningful information regarding the normalized rate of consumption of energy resources during a defined period of time (e.g., Btu/GSF yr). However, they provide no information regarding the effectiveness of the energy used to provide for the functional performance of buildings. Other metrics are needed, such as tenant or occupant responses, occupant or tenant performance, productivity, and economic rates of ROI. To reduce uncertainties, these functional performance metrics must be quantitatively measurable, valid, repeatable, reliable, and accurate.




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  posted on 4/5/2015   Article Use Policy

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