Spotlight Series with Jim Lubratt

How to Evaluate Building Leakage Losses with

AQC’s Q Duct and Energy Savings Calculator

The commercial HVAC industry is searching for energy-inefficient sources to help make each project as efficient as possible. Our industry has accepted duct leakage in the past because we all once thought that a price competitive zero-leakage duct system does not exist. Well, for the past five years, it has been on the market. It’s called Q Duct- manufactured by AQC Industries (www.aqcind.com). Q Duct is challenging the industry to realize that significant energy is lost from traditional outdoor duct systems’ leakage. AQC Energy Calculator

To quantify the potential savings, AQC has added an energy saving calculator to its website. The user will quickly see that a Q Duct system with its standard SMACNA leakage class 1 and R-12 will always outperform a comparison duct with SMACNA leakage class 3, which is still an industry-low leakage rate, and double the insulation at R-24. 

How does the AQC Energy Calculator work?

The calculator has a set of equations explicitly created to determine a duct’s overall performance based on heat transfer properties. These equations are detailed in a white paper that is available for download from the calculator. AQC determined each rooftop duct system generates energy losses in three main areas: leakage, conduction losses from both insulation and thermal bridging, and losses from fans moving excess air fully lost to the atmosphere. Using ASHRAE climate data, the energy loss is evaluated in each of these three areas for heating and cooling, leading to a total annual energy loss from the (assuming a 24-hour a day, 365-day a year operation) outdoor duct system.

The total energy loss for Q Duct’s near-zero leakage system is compared to the total energy loss of a comparison duct system to find overall energy savings with the Q Duct system. The calculations use AQC’s Q Duct specifications and a comparison’s duct specifications, illustrating that air leakage is the primary energy impact. AQC’s Q Duct exceeds a SMACNA leakage class of 1, while almost all other duct systems have a three or higher leakage class.

The calculator also outputs the peak energy loss in kilowatts for both heating and cooling to aid the utility companies in quantifying a possible rebate.

Inputs and Outputs

Go to the AQC energy calculator and input a few specifics related to your project. Specific inputs include state, city, natural gas & electric rates (each pre-loaded with the national average), duct area, and pressure class along with the R-value and SMACNA leakage class for Q Duct and the comparison duct. Even though Q Duct is standard with SMACNA 1, most of our tested projects have shown zero leakage; hence, a 0.5 leakage class is listed. Also, an R-1 is offered as an option for the calculator even though it is not available to illustrate the impact of leakage over duct insulation value.

The calculator offers an Advanced option that allows the user to change the 4 points from ASHRAE’s weather data that includes the heating and cooling degree days, along with the Heating and Cooling design temperatures. Also, the advanced area allows the user to edit the cooling efficiency, heating efficiency, heating type, fan efficiency, and area of the comparison’s duct 4-bolt flange.

Outputs graphically illustrate the energy savings of Q Duct and the comparison duct. The user can take their cursor to hover over a bar in the bar graph to see the cost of each component of the energy losses. The calculator will also output the peak energy savings in both heating and cooling to assist local utilities with rebate calculations.

Why choose AQC’s Q Duct? 

Rooftop duct systems are unique because they are exposed to the outside elements. Hence, external, ductwork energy losses are unrecoverable. In contrast, building owners can fractionally recover losses from interior ductwork. The main contributing factor to outdoor energy losses is leakage. “AQC’s new energy calculator is a fantastic and eye-opening tool.  Duct leakage is real; and unfortunately, all too accepted by our industry.  This calculator quantifies the losses we live with daily if we continue to accept the status-quo and not move forward with new energy-saving technology, even if that technology is something as simple as a duct that does not leak.” Jim Lubratt, SVL. Since the beginning, our industry has accepted duct leakage because no such zero or near-zero leakage system existed until Q Duct. AQC invented its unique quadruple interlocking system called Q Lok to address the massive energy lost through leakage. AQC’s Q Duct’s Q-Lok design reduces the leakage to SMACNA class to 1, or better, which is the best possible class. Overall, why should someone pay to heat or cool air to lose it to the atmosphere instead? AQC challenges designers to specify SMACNA leakage class 1 and a field leakage test to verify the performance. AQC says, “Don’t worry, we’ll exceed it.”

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