Seventhwave pushes the ‘energy-efficiency envelope’ in commercial and residential buildings

By Better Buildings Beat Team on Jul 14, 2017

Better Buildings Affiliate Seventhwave advances sustainability as an independent non-profit through energy consulting, continuing education, research and program design for the residential and commercial building sectors. Want a piece of their institutional wisdom? Based on recent projects, Seventhwave is sharing strategies for garnering efficiencies in both residential and commercial sectors.   

Watch Window-to-Wall Ratio in High Rise Residential Buildings

Seventhwave recently teamed with northern Illinois-based energy delivery company, ComEd, to deliver a series of events and topics related to window to wall ratio and Chicago’s path to deep efficiency. One energy-efficiency approach Seventhwave recommends for the design of high-rise residential buildings is a 40 percent window-to-wall ratio (WWR). This design choice allows for an increase in usable daylight and extending hours with window shades open. These improvements provide added comfort and reduce energy consumption at the same time. Additionally, costs can be reduced through an optimized façade design using a true integrative approach, including solar heat gain coefficient glazing, exterior shading, and other advanced window technologies. In the case of floor-to-ceiling glass, these exterior design features are less effective and in many cases, a hindrance. A building with a 40 percent WWR can be a finely-tuned, inspiring, and superior addition to a developer’s portfolio.

“When you think all-glass façade, think 20-25 percent more building energy consumption,” said Brett Bridgeland, a Seventhwave engineer who supports the ComEd Energy Efficiency Program, at a recent ComEd-hosted event in Chicago focused on building envelope. “When you think less glass, think more daylight, comfort, privacy and views.” For more details including links to the presentation slides, technical paper, blog and webinar visit

Get Serious about Plugloads in Commercial Office Space

Plug load energy is all around us. It’s in computers, copiers and water coolers, and it represents a mostly unrecognized energy-saving opportunity. Particularly for commercial buildings, this relatively simple solution can make a substantial difference.

With funding from a grant by the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program, Seventhwave tested several equipment strategies to reduce office plug loads in commercial buildings. By installing computer power management (CPM) systems, the research found that each workspace can save 106 kWh per year and reduce energy consumption by 29.1 percent on average. This approach saved the most at almost every office site.

Other office plug load solutions tested by Seventhwave include APS with occupancy sensors and APS with foot pedals. They also tested a behavior campaign that included education via posters and emails, LED light feedback indicating whether the power strip was on or not, and rewards to people demonstrating energy-saving behavior.

Is there an opportunity to reduce office plug loads in your building? Check out Seventhwave’s research for more strategies commercial buildings can take to shrink these loads.

Hug Your Rooftop Units

According to Seventhwave’s research on implementing RTUs, rooftop units have become the focus for energy-efficiency programs because they take up a substantial share of the HVAC market. The more popular RTUs become, the more time manufacturers can dedicate to developing complex functionality, and thus efficiency. In their findings, Seventhwave outlines a number of recommendations for increased efficiency that could be added to a comprehensive RTU program, including the following:

  • Demand control ventilation: reduce ventilation during unoccupied periods: use carbon dioxide or occupancy sensors to save the energy needed to heat or cool outside air.
  • Improved economizers: ensure that the outdoor air dampers do not let in unconditioned air when closed. Also ensure that the economizer is working properly through advanced fault detection.
  • Casing insulation: properly insulate the RTU casing to reduce heating and cooling loads to the building.
  • Efficiency supply fan: increase supply fan efficiency through improved blade design. Also, direct drive motors reduce frictional losses as compared to belt driven fans, boosting overall fan system efficiency.
  • Condensing gas-fired heat exchanger: capture the latent heat in the combustion exhaust to increase the heating efficiency of gas-fired RTUs to 90-95 percent.
  • Energy recovery ventilation: use a sensible or latent heat exchanger to recover energy from the exhaust air stream to preheat incoming ventilation air.
  • Evaporative cooling retrofit packages: add evaporative cooling kits to existing RTUs to increase cooling efficiency by allowing condensing temperatures to approach outside air wet-bulb temperature as opposed to dry-bulb temperature.
  • Increasingly sophisticated and intelligent controls: add controls capable of precisely controlling RTU operation to optimize energy performance, as well as detect faults and alert maintenance staff to address degraded performance quickly.

Source: Recommendations taken from page 6 of the Commercial Roof-Top Units in Minnesota Report

The most common barrier to capturing these savings through new technology is the capital cost. Fortunately, many local utility programs have rebates available to lower the barrier to higher efficiency units. These rebates, however, have been based on exceeding a minimum full load efficiency. While this makes sense for utility programs whose priority is peak demand reduction, the trend in efficiency for RTUs is leaning towards part load efficiency. Seventhwave recommends developing rebates based on the Integrated Energy Efficiency Ratio (IEER), which would benefit utility programs whose priority is annual energy savings.

For more information on advancing your buildings RTU, check out the Advanced RTU Campaign.

Seventhwave’s RTU study was made possible by a grant from the Minnesota Department of Commerce, Division of Energy Resources through CARD, which is funded by Minnesota ratepayers.

To explore more research and insight from Seventhwave, visit and learn how you can make your building more efficient.