November-December 2009

The Concept of Commissioning

To achieve a well-constructed building, all components and systems must work together as intended to optimize energy consumption.

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By George Leposky

3 Comments


The actual testing of an average 120,000–square-foot building of moderate complexity may take two to four weeks, but Barber notes that it doesn’t all have to happen at one time. It can occur in a phased sequence as individual systems reach completion.

“Most office buildings take 12 to 24 months to build, depending on the size of the building, the urgency involved, the labor force, material availability, contractors, and the weather,” says Faircloth. “Then the commissioning provider typically will come back about 10 months after the owner takes over, and go back through the process again to verify that the building is still functioning as commissioned. If it’s not, he will try to determine what happened, whether something changed, or whether the maintenance staff didn’t receive enough training.”

Ideally, a commissioned building should be recommissioned every three or four years throughout its useful life to see if anything has changed, and to make any adjustments that may be necessary. Faircloth says recommissioning a building can take anywhere from a day to a week.

Barber uses the term “ongoing commissioning” to describe constant monitoring of certain parameters to confirm the efficiency and effectiveness of specific systems, especially climate control. “If we’re serious about reducing a building’s carbon footprint on a long-term basis, we should provide for constant monitoring,” he says. “When we put in the building’s automation system, we should build in sensors in strategic places to monitor electrical power consumption on certain circuits, and natural gas input to the chiller and output in Btus.

“The trick is to have someone knowledgeable who can review printouts periodically and say the chiller isn’t as efficient as it used to be—we have trouble keeping the air handlers and the end of the piping run cool like we used to,” he continues. “Some facilities have sophisticated staff that can do this in-house.

“For others, there are firms that specialize in downloading this information periodically and sending you reports,” he says. “Then, if something is wrong, you can call the commissioning agent to test the chiller to find the problems, or look at the building to see what has changed.”

Sometimes those changes are obvious. An open retail store becomes an office building in which an owner or tenant erects interior walls without considering their effect on airflows. An office building adds computers, servers, and other heat-generating equipment over time, increasing the building’s cooling requirements.

And sometimes the changes are subtler. Perhaps a pump has failed and has been replaced, but the maintenance staff wasn’t sure how to set the replacement for optimum performance. Perhaps the schedules of people using the building have changed, increasing demand on the lighting and climate-control systems at times when the building originally was supposed to be empty. “When I’ve come back as little as three years after commissioning a building, I’m amazed at how much can change,” says Barber.

Retro-commissioning may take between a day and several weeks, depending on the availability of a building’s original construction documents and their level of detail, the availability or lack of built-in monitoring systems, and the amount of testing that may be necessary.

Cost and Payback
In general, Faircloth says, the cost of commissioning ranges from 0.5% to 1.5% of construction costs, with the percentage higher for small buildings than for large ones.

The most definitive analysis of the costs and benefits of commissioning comes from a 2004 study, The Cost-Effectiveness of Commercial-Buildings Commissioning, prepared for the US Department of Energy by researchers at Lawrence Berkeley National Laboratory in Berkeley, CA; an Oregon-based non-profit organization, Portland Energy Conservation, Inc. (PECI); and the Energy Systems Laboratory at Texas A&M University in College Station, TX.

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For existing buildings in the study, the median commissioning cost was 27 cents a square foot, median whole-building energy savings were 15%, and the median payback time was 0.7 years.

The new buildings had a median commissioning cost of $1 a square foot (0.6% of total construction costs) and a median payback time of 4.8 years. Next Page >

What Do You Think?

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conltgint

December 17th, 2009 8:53 AM PT

The article on commissioning was an eye opener. It is really needed from beginning concepts to completion of construction and thereafter. It might elimate the kind of "value engineering" that dilute the original design for the purpose, and the lack of scheduled maintenance provided. However, only Leonardo DaVinci's brain could be fully familiar with ALL the disciplines and trades, plus the myriad of codes and standards in each location. This means that not one "commissioning authority", but a knowledgeable team of specialists is essential to do a proper job. And who is going to bell the cat to decide which are the right practitioners for the job? Many a board or committee has favorite candidates that may not fit the bill professionally.

greg chick

December 5th, 2009 5:23 PM PT

Residential commissioning is not a bad idea either. Homeowners need to know how to use the home better too! Techie stuff is now common in residential. Greg Chick

glassfiber

December 2nd, 2009 8:59 AM PT

Good commissioning would require a team, not just an individual, because one person cannot know all the codes and standards in every municipality and state, as well as federal. The participants would also have to be regional. Expert knowledge of the building envelope, HVAC, domestic hot water, power and lighting, in addition to decorative features is needed to create design that is green, sustainable, energy efficient and reduces greenhouse gases. Introduction of modern mechanical/electrical systems, expected by today's occupants, into millions of structures never having them before, is a special case. It requires knowledge of older construction methods and materials in order to do the job on time, on budget and sensitive to original design and fabric. Commissioning is a great idea to have such a watchdog, but it should not turn into another bureaucratic hurdle.

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