Author: Sherri Shields

In The Field With Neil: RESNET-Approved Airflow Measurement Techniques

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Chapter 8, section 804 of the RESNET Standard provides us with an onsite procedure for measuring the airflow of ventilation systems. These procedures treat the air flows into a grille and out of a register measured separately. There are 3 RESNET-approved test processes used to determine airflow: 1) powered flow hood, 2) air flow resistance and 3) timed bag inflation. Each method, as most things in life, has positives and negatives.

 

Powered Flow Hood

powerflow

The powered flow hood method is the most accurate, but also the most expensive. The powered flow hood differs from a conventional flow hood in that there is a fan which assists air movement through the flow hood to prevent a pressure differential at the register or grill created by the flow hood. The most common is the Energy Conservatory FlowBlaster® which works with your existing Duct Blaster Fan and DG-700 Pressure and Flow Gauge. The fan is powered by a combination fan speed controller and rechargeable Lithium-Ion battery. This method may be used on either exhaust or supply systems.

 

Air Flow Resistance

airflow

The air flow resistance method is probably the most common and can only be used on exhaust systems (air entering grill).  This method determines the air flow by measuring a pressure difference across a known hole size.  The air flow (in cfm) is equal to the hole size (in square inches) times 1.07 times the square root of the pressure difference (in pascals).  (Yes we are mixing units, but the 1.07 factor takes care of the conversions.)  This device will give the best results when the pressure difference is less than 8 pascals – largely because the exhaust fan speed will be reduced with greater pressures.  There is a commercially available “box” or flow meter again from the Energy Conservatory or you can easily create your own.  (If interested in creating your own – drop me a line and I will send you the directions.)

 

bag

Timed Bag Inflation

The timed bag inflation method is the least expensive of all.  It can only be used on supply systems.  As the name implies, a bag (typical a garbage bag) of known volume is inflated by the supply air.  The time required to fully inflate the bag is measured with a stopwatch.  This method takes a bit of practice to get repeatable results, but is rather simple to do.  As the standard indicates, bag volume and thickness play into the accuracy of the results – so a trial and error approach is needed.  Aim for a fill time of 2 to 20 seconds – the longer fill time will be easier to do, but may require a fairly large bag depending on the amount of airflow.  The airflow is easily calculated by multiplying the bag volume (in gallons) by 8 and dividing by the time (in seconds) required to fill it.  The Canada Mortgage and Housing Corporation has a nice write up on the method along with a table to convert to airflow.

 

These three procedures are the only RESNET-approved methods for measuring airflow in either whole house or spot ventilation systems.  (Well, there is one exception – if an ERV/HRV manufacturer has ports installed on their device for the purpose of measuring airflow; that may be used when following their directions.)

So go measure and have fun out there…

UCF Professor Wins Research Incentive Award

Sherri Shields Awards, Energy News 3 Comments

By Danielle Daniel

Congratulations to Dr. Nahid Mohajeri, who received a University of Central Florida (UCF) 2012-2013 Research Incentive Award in recognition of her exceptional research efforts. Dr. Mohajeri is an associate research professor at UCF’s Florida Solar Energy Center (FSEC).

Professor Nahid Mohajeri

Each year, UCF recognizes faculty members and research staff who have an outstanding research, scholarly, or creative record that advances the body of knowledge in their field.

“I did not get here all by myself,” states Mohajeri, in response to receiving the award. “I have been helped, guided, and given opportunities by many people during my tenure at FSEC that I will forever be grateful,” she explains.

Dr. Mohajeri’s recent contributions to the research community include the development of highly durable proton exchange composite membranes for fuel cells, a technology based on the addition of cerium oxide nanoparticles to the membrane. When tested, this innovative approach   improved fuel cells’ membrane stability and performance, resulting in a sevenfold decrease in the open circuit voltage decay rate compared to the baseline membrane. Membranes are at the heart of hydrogen fuel cell technology, and by increasing their durability, goals for developing fuel cells as a reliable, alternate energy source are attainable.

Other accomplishments include the creation of a chemochromic hydrogen leak detection tool known as “Smart Paint,” which was used by NASA to visually detect colorless and odorless hydrogen leaks. Furthermore, Dr. Mohajeri discovered a new class of catalysts for the hydrolytic cleavage of ammonia borane, one of the promising classes of chemical hydrides for hydrogen storage. She has authored and co-authored more than 30 scientific publications and has received seven patents (awarded and applied). In addition to her research endeavors, Dr. Mohajeri says she considers it an honor as a professor to educate and mentor “the next generation of scientists.”

Regarding future contributions to energy research, Dr. Mohajeri’s diverse background has enabled her to work in various energy research areas. However, one focus in particular has garnered her attention: “The area of soft materials, such as polymers, for energy storage or energy efficiency technologies holds a special place in my overall interests in energy research,” she states.

Solar Electric System Provides Emergency Power and Teaching Tool for Haines City High School

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By Sherri Shields

COCOA, May 17, 2013 – Students, teachers and the community of Haines City will reap multiple benefits from the new 10,000-watt photovoltaic (PV) system at Haines City High School. The PV system with battery backup will provide emergency power during an outage, reduce daily electricity costs to the school, and serve as a learning resource.

Haines City High School celebrates new 10,000 watt solar electric system with ribbon cutting and solar workshop for teachers. (From left to right, Mike Vergona, Vergona-Bowersox Electric Inc.; Caroline Weaver, Polk County Energy Manager; Peter DeNapoli, Solar World Eastern Region Manager; Patricia Butler, Haines City High School Principal; Stephen Scheloske, Haines City High School Assistant Principal ; Sherri Shields, FSEC Communications; Susan Schleith, FSEC SunSmart E-Shelter Program Manager. Photo Credit: Nick Waters

The Florida Solar Energy Center (FSEC), a research institute of the University of Central Florida (UCF), held a dedication ceremony and solar workshop for teachers to celebrate the installation of the 42-panel PV system at Haines City High School on Wednesday, May 15th. Coordinated by UCF’s Florida Solar Energy Center, the system, valued at $85,000, is the 85th PV system installed through the SunSmart Schools Emergency Shelter Program.

In conjunction with the dedication, a professional development workshop gave teachers from Haines City High School, Poinciana Academy of Fine Arts in Osceola County, Bloomingdale High School in Hillsborough County and Montessori World School in Orange County an opportunity to experience hands-on solar activities, showcasing the FSEC curriculum and a companion renewable energy kit. More than 250 teachers have participated in similar workshops, impacting more than 50,000 students statewide.

Teachers participate in a hands-on professional development solar workshop (From left to right: Broderic Ogzewalla, Robin Anderson, and Britton Bouey from Haines City High School, and Raf Baksh from Bloomingdale High School). Photo Credit: Nick Waters

Not only does the PV system reduce electricity costs by up to $1,500 a year and serve as a generator when a power outage occurs, the system also reports performance data to FSEC; the data will be available on energywhiz.com in June. This site will allow students and teachers to analyze PV system performance data to better understand how the technology works. “We hope we never have to use the system as a generator, and we’re excited about the hand-on learning application for our students and teachers. Being able to see the real-time data that our system produces will be a tremendous resource,” said Stephen Scheloske, assistant principal at Haines City High School. Read more

Renewable Energy Student Teams Energized Even on a Cloudy Day

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COCOA, May 09, 2013— With clouds in the sky and all eyes on the weather, more than 600 elementary, middle and high school students were energized on Saturday, May 4th. Student teams—from Key West to as far away as North Carolina—gathered at UCF’s Florida Solar Energy Center on Saturday to demonstrate their Science, Technology, Engineering, Art and Math (STEAM) skills by competing at the 11th annual EnergyWhiz Olympics.

Cocoa Mayor Henry Parrish III speaks into megaphone.
Cocoa Mayor Henry Parrish III welcomes crowd to EnergyWhiz Olympics.

The daylong event started out cloudy and posed challenges to the solar-dependent competitions, especially the Bright House Solar Energy Cook-off and the Junior Solar Sprint (solar-powered model car) teams. Although weather conditions were less than ideal, the sun managed to peek through the clouds and provide just enough energy for the teams to get through the solar competitions. And although Energy Innovations, a full-scale solar electric design and marketing challenge, depend on the sun for their complete product demonstration, teams also created marketing pieces—such as brochures, fliers, and posters—to promote their product.

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In The Field With Neil: Automatic Fan Control

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Most of us use either the Energy Conservatory DG-700 or Retrotec DM-2 digital micromanometers.  These meters have some great, yet under utilized features.  I would like to introduce you to one of the features – automatic fan control.  The Energy Conservatory refers to it as “cruise control” and Retrotec as “set pressure”.  In either case, it allows the digital pressure meter to control the fan speed or flow based on the pressure of “A” channel.

With the Automated Control you can…

  • quickly measure building airtightness using a “one-point” 50 Pa test.
  • quickly measure duct airtightness using a “one-point” 25 Pa total leakage test.
  • simultaneously control both the blower door and duct tester fans during a leakage to outside duct airtightness test. During this test, the meter will maintain a constant 25 Pa building pressure while the gauge connected to the duct tester fan maintains a constant 0 Pa pressure in the duct system.
  • maintain a constant building pressure while pressure pan testing, or locating and sealing building and duct system air leaks.
  • perform series leakage to quantify leakage rates between various zones within a building.  (Check out our class on Advanced Pressure Diagnostics…we will be using the cruise control a lot)

So this sounds great – what do you need in order to use the automated fan control feature?

  • An “automated fan compatible” gauge. Most are, but check that it has either “EC-cruise” or “Retrotec-set pressure” buttons on the front panel of your digital pressure gauge.
  • A blower door or duct tester fan speed controller with proper communication jack.
  • A cable to connect the meter to the fan.

That is it!  And you probably already have everything you need – especially if you recently purchased your equipment.  So next time you are out in the field – give it a try; I know you will ask yourself, ‘how did I ever get along without this?’.

For more information on automated blower door control: