Solving TAB issues with duct sealing also realizes huge energy savings for Alexandra Hospital


92% leakage reduction


Alexandra Hospital


Ingersoll, ON


Increase HVAC air exchange rate

Before Sealing

18,550 CFM leakage

After Sealing

1,484 CFM Leakage

When administrators at Alexandra Hospital received TAB reports indicating that the building’s HVAC system was not providing sufficient rates of air exchange, they called Nerva for recommendations. With duct leakage at the heart of the problem, we found options limited: either upgrade the entire system or manually seal the ductwork. Both operations were prohibitively expensive and disruptive. With much of the ductwork hidden behind walls and covered in insulation, the cost of manual sealing was estimated at more than $1 million. And that didn’t even include the cost of the demolition and reconstruction necessary to access the ducts. We suggested the hospital consider using a our new duct sealing technology that works from inside the ducts to find and seal leaks. The unique inside/out approach would provide easy access without demolition and was a fraction of the cost of other options. Best of all, it was highly effective and the technology had been successfully used at other hospitals globally.

The process began by first conducting a full audit of the HVAC system. The amount of air coming out of each register was measured, and the energy required to operate the three main air handling units and the one exhaust system included in the first phase of the project was calculated. In less than two weeks, sealing was completed, and post-testing found that the sealing of the ducts increased CFM output by an average of 27%.

With the higher rate of air flow, we were able to replace the constant fans with variable frequency drives (VFD) and other equipment that would reduce overall energy usage. Post-seal measurements showed that VFDs will cut fan energy usage almost in half. Chilled and hot water usage through the coils will be reduced by 27%, which reduces the load on every air handling unit by 27%. The steam boiler’s output for each air handler will also be reduced by an equal amount. Detailed modeling revealed potential annual energy savings of $59,321.

Within the first night of sealing, the CFMs that were leaking out of the system were restored, and the leaks were 90-95% sealed, so we were able to move all that extra volume of air throughout the departments the way the system was designed. Going in was less invasive, and the time it took to seal was cut to 1/3 of the projected time it would have taken to seal manually.

– Tim Foster, Head of Maintenance, Alexandra Hospital