Did you know that 8.5% of U.S. residents live in large multifamily buildings with 20 or more units? Despite the large number of U.S. households in multifamily buildings, energy efficiency is often overlooked in this sector. And it can be tricky to address, largely because multifamily building characteristics vary drastically — there isn’t a one-size-fits all approach. Fortunately, CEE research to be released later this year will offer new ways to look at multifamily energy efficiency.

In the meantime, CEE researchers have come up with a new tool to help our research and, in the long run, to help multifamily building owners and managers operate more efficiently.

CEE’s researchers understand that ventilation is a critically important, and often overlooked, piece of the puzzle. Although just one of many factors in energy cost savings, ventilation is a key source of energy savings in Minnesota, where the majority of multifamily buildings were built in the 1960’s or later; ventilation problems are often intensified in newer, more airtight construction.

In multifamily settings, ventilation accounts for up to 6% of electric use in common spaces and up to 30% of space heating building-wide. In many cases, the energy used by ventilation systems can be reduced by as much as 50% by simply reducing excessive airflow from oversized or maladjusted ventilation equipment. This simple and inexpensive adjustment can improve ventilation performance, save energy, and reduce equipment operation and maintenance costs in one fell swoop.

In 2012, CEE began a comprehensive study of energy improvement opportunities for multifamily ventilation systems, including cost-effective ways to measure, diagnose, and retrofit these systems. While researching techniques and recommendations to assess and improve ventilation, the project also unleashed an exciting and unexpected outcome: the development of a new diagnostic device!

Until now, measuring exhaust ventilation in any standardized way has gone largely unexplored. Because of expensive customization needed to accommodate the huge range of fan sizes and configurations in multifamily buildings, rooftop exhaust ventilation airflow is rarely measured. For a rooftop with 20 exhaust fans, for example, the process would generally take at least two full days; measuring each fan would require 2-3 hours with customized equipment (adapters, calibrated fans, capture hoods, etc.).

To reduce the time, tedium, and people power needed to measure large-volume airflows, CEE experimented with many customized devices, but nothing worked quite right. So prominent energy field expert and CEE senior building analyst Jim Fitzgerald [bio link] put his creative and technical ingenuity to work, setting out for a solution to fundamentally improve upon the accuracy, time investment, and convenience of previous methods.

The harsh conditions of high-rise apartment rooftops can be less than ideal or, as Jim puts it, “not my idea of a vacation spot.” Working in 30 mph gusts at 25 stories, and sometimes even lying in puddles of rainwater to take measurements, motivated Jim to think outside the box to develop a new approach.

Jim calls his creation a “TrueFlow capture box,” displaying the brand name of The Energy Conservatory’s Trueflow metering plates, which are fitted to the top of a collapsible box. Although still mostly a homemade tool, the capture box has been refined many times over, employing familiar equipment in new ways. In its latest iteration, corrugated plastic sides are well-taped to create a cube-shaped capture hood that can be folded for easy and light transport. The box’s lid is fitted with metering plates and fastened to the top of the capture cube. The cube is then placed over the rooftop fan to measure airflow in minutes using a battery powered digital pressure gauge.

Jim’s simple device won’t win points for beauty, but that’s a worthwhile tradeoff for accuracy.

CEE’s TrueFlow capture box measures ventilation levels with just a sliver of error. Based on many tests and comparisons, the capture box consistently measures with less than 2% error, well under the 5% industry standard for margin of error. In addition to increased accuracy, the device makes testing safer, more portable, and much faster — taking a few hours instead of a few days.

So how will CEE’s capture box help multifamily building owners or operators? Reducing ventilation measurement time by 80%-90% also reduces testing costs significantly, which should increase the likelihood of including this critical diagnostic in building inspection routines. This could lead to the discovery of even more energy savings at a low initial cost for property owners. In addition, the exceptional accuracy allows energy professionals to include precise investment analysis with their recommendations, crucial information to illustrate the value of energy retrofits.

Once again, necessity has proven to be the mother of invention. And it’s especially lucky in this case that extreme conditions paved CEE’s way to extreme innovation.

Truong Duy