The Sustainability Institute


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The Sustainability Institute

Comfort, zone control, energy savings. These were a few of the requirements The Sustainability Institute (SI), Charleston, S.C., required when it came time to retrofit the HVAC system at 113 Calhoun Street.

SI is an award-winning, nonprofit, 501c(3) organization with a mission of empowering South Carolinians to conserve energy and reduce the environmental footprint where they live and work. SI and CharlestonWISE, its performance assessment and construction partner, offer comprehensive home performance assessments, ASHRAE-level commercial energy audits and residential general contracting.


Challenge: The Sustainability Institute required an energy-efficient, zone-based, non-invasive HVAC solution for an historic retrofit installation.


SI is an award-winning, nonprofit, 501c(3) organization with a mission of empowering South Carolinians to conserve energy and reduce the environmental footprint where they live and work. SI and CharlestonWISE, its performance assessment and construction partner, offer comprehensive home performance assessments, ASHRAE-level commercial energy audits and residential general contracting.

In 2010, SI purchased the 113 Calhoun Street property to use as an office space as well as serve as a showcase to its customers. The property, a Charleston Single House built around 1880, had been previously owned jointly by several entities whose focus had been to renovate the historic property, providing an example of sustainable building practices and resistance to natural hazards, such as wind, floods and earthquakes. This overall focus would continue for SI, but many changes were needed to meet that goal.

SI is quite familiar with ductless cooling and heating systems, as CharlestonWISE specifies many of these systems for its customers. As part of a normal scope of work for the building, they performed a pre-retrofit assessment, including blower door and duct blaster diagnostic testing as well as energy modeling.

“From the energy model, we projected that a mini-split system would save us about 50 percent in energy costs compared to the existing HVAC system. The systems greatly exceeded those savings, and the building has been a much more comfortable place to work,” said CharlestonWISE Manager, Joe Dukes, LEED AP.

Once SI determined that ductless was the way to go, a Mitsubishi Electric US Cooling & Heating Division (Mitsubishi Electric) system was selected for the job. “Because Mitsubishi Electric systems are so easy to install and minimally invasive, they were the perfect choice for The Sustainability Institute,” said Medd Box, president, AirMax, Charleston, S.C.

Since 113 Calhoun Street would serve as a showcase, highlighting various technologies, SI chose to incorporate four different types of indoor units into this system so that customers could see for themselves how each unit type might look in a home. The property incorporates the following indoor units in a seven-zone system: wall-mounted, horizontal-ducted, floor-mounted and one 4-way cassette.


Solution: A seven-zone Mitsubishi Electric system helped The Sustainability Institute realize a 75 percent reduction in energy costs.


“Another extremely beneficial aspect of the Mitsubishi Electric product is that the outdoor units are so lightweight,” said Box. “Charleston is in the low country, meaning we are at or below sea level. As such, it’s best if the outdoor units can be installed off the ground. For this installation, the outdoor units are hung on the home’s exterior wall, away from the street.”

An added bonus for SI was that the ductwork installed in a previous renovation was removed. This freed up ceiling space and reclaimed enough space indoors to install a full-sized kitchen where previously there had only been enough space for a kitchenette. Additionally, the office staff appreciates the individualized temperature control for each zone.

The Mitsubishi Electric installation was completed in July 2013 and in the short time since, SI has already realized considerable energy savings. Compared to August 2012, energy savings in August 2013 was 75 percent, a full 25 percent higher than projected. SI offers tours of the property by appointment, and the facility is available for workshops and for special events. The property also serves as a research laboratory and energy usage monitoring is ongoing.

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