Because salaries typically make up more than 90 percent of the total operating cost of a commercial building, even tiny increases in employee productivity can mean a lot to a company's bottom line. Studies have shown, for in-stance, that just a 3-percent productivity gain can translate into a nearly $3 million gain in a 500,000-square-foot facility.

Before determining what the root cause of a comfort complaint might be (e.g., lack of proper zoning, poor workspace design, lack of ventilation) and taking corrective action, facilities managers must first figure out whether the subject area is in fact too hot or too cold.

Getting Answers

To validate temperature-related comfort complaints, an increasing number of facilities managers and HVAC contractors are relying on battery-powered data loggers. Data loggers are low-cost, compact instruments that incorporate built-in microprocessing, high-accuracy temperature sensing, recording, and battery power in a self-contained package.

Temperature data loggers employ sensors that can measure temperature, relative humidity, light, and other parameters. The logger monitors and records at user-defined intervals (e.g., every 10 minutes) and stores it digitally into its onboard memory. Many temperature loggers are small enough to be placed in hidden, out-of-the-way locations to gather information in a workspace without being seen or disturbed.

Depending on the amount of built-in memory and the interval for taking readings, data loggers can realistically collect data for several months at a time before reaching their full capacity.

According to Steve Walker, an HVAC supervisor for Framingham, Mass.-based Genzyme Corp., data loggers have been an important tool in investigating comfort complaints at the company's 11-building campus.

"In one of the administration buildings, employees were complaining about their feet being cold," said Walker.

"We put data loggers underneath desks in the area and actually showed that the air was 4 to 6 degrees Fahrenheit colder than the air above the desks. From this, we were able to determine that there was not enough velocity of heat coming out of the registers to get the air to circulate under the desks, which were built into the walls.

"Realizing there was a problem in how the workspace was configured, we went back to the design firm and had them make modifications in the configuration."

Ron Mincks, a district energy manager for the Rapid City School District in South Dakota, also uses data loggers to investigate comfort complaints from teachers and other school employees.

"When a teacher complains about classroom temperature," he explained, "we are now able to monitor conditions very easily. In one building I had computerized univents, and the custodian had them coming on at 7 a.m. The teacher was saying that at 9 a.m. the room was cold. We couldn't figure why the room would still be cold, so we deployed a few data loggers. From the data we were able to determine that a computer operation glitch was causing the temperature to drop."

Mincks said that just the process of using data loggers can help with comfort issues.

"We've really increased student and teacher comfort just by documenting temperature." Mincks uses loggers on an ongoing basis to verify that classroom thermostats are working properly. He collects a daily log of temperatures in the classrooms.

How To Use Data Loggers

Using a data logger properly involves four basic steps:

1. Logger setup - Setting up a logger is typically done by connecting the device to a PC and using the logger's software to make a number of point-and-click selections. These include how often the logger should take a temperature measurement and the specific data and time the logger should start recording.

2. Deployment - This involves determining optimal placement of the logger(s) in the workspace and placing the logger in the area.

3. Data retrieval - This involves offloading the collected data onto a PC, laptop, or data shuttle.

4. Analysis - Data analysis is typically performed using accompanying data logger software. It allows the facilities manager to translate the temperature data into time- and date-stamped graphs that show spikes and drops in temperature during the given data collection period.

This temperature data offers facilities managers an accurate and complete picture of the actual temperature activity that occurred throughout the entire monitoring period. The data, in turn, can be used to determine where problems exist.

Features And Capabilities

When evaluating data loggers, there are a number of features and capabilities to consider.

It's a good idea to make sure the logger offers an option for offloading data without having to bring the logger back to an office PC each time. Dedicated data logger "shuttles" allow users to retrieve data from loggers deployed throughout a facility, quickly and conveniently.

Make sure the logger's software lets you perform tasks such as configuring parameters, launching the logger, and offloading data with point-and-click simplicity. At the same time, it should offer data-plotting capabilities and enable you to export data to other programs, such as Microsoft Excel, for analysis.

Look closely at the total cost of ownership when shopping for a data logger.

Here are some questions you may want to ask your supplier:

Will the logger need to be calibrated by the manufacturer periodically, and if so, what are the cost implications over time?

Will I need to invest in a software package to analyze results?

Will I be able to use the AA batteries, or will the logger require a different power source?

Although facilities managers may never be able to put a complete stop to the "too hot/too cold" battle, they at least have access to affordable tools that can validate the complaints.

Evan Lubofsky works with Onset Computer Corp. For more information, call 800-564-4377 or visit www.onsetcomp.com.

Publication date: 01/17/2005