Arkansas HVACR NewsMagazine March 2026

HVACR NewsMagazine March 2026

Tech News

reflect light and heat, sometimes moving the reflected loads to neighboring offices. This was the same technology that improved thermos bottles just a decade prior. Next came aluminum double pane windows. Double pane modules lost integrity early on making the first-generation windows short lived. In the late 1990’s a shading technology with mild reflectivity built in was the first generation of “Low E” window. In the mid 2000’s, code mandated “Low E” fenestration. Today’s windows are improved with be tter materials, lower air flow, and thermal conductivity however, the phrase “windows make a terrible wall” remains a common term.

handling equipment utilizing variable speed technology would attempt to overcome poor duct using more energy in the process. In the cooling retrofit market, heat only systems had ducts that were too small or inaccessible to move required air efficiently. Only steel duct manufacturers were calling foul on flexible duct that had been installed over the past two decades. Due to the ease of installation and lower material costs contractors were reluctant to question engineering data provided with the flex. This unintended consequence of duct testing in the late 1990’s shined a light that has only recently improved upon over the last several Code cycles moving from R4 insulation to the current requirements dependent upon climate region, and with sizing increases for efficient air flow. Turns out if flexible duct is installed as the manufacturer intended, the differences in performance are minimal compared to steel duct. Restricted air flows By analyzing poor air delivery, engineering data validated duct sizing needed to be revisited both on the fan side, and the return or cold air side. This is why the old rule of one square foot of return air grill per ton in the 1980’s has been replaced w ith the current two hundred square inches per ton or more depending on the face velocity required for proper filter function. Filters themselves continue to be the biggest chokepoint in air delivery to date. You must be familiar with all brands and real-time applications of materials. Deep pleated, multiple housed filters are required on all but 18,000 BTU air handling equipment if you are to move air efficiently.

Courtesy healthbuildingscience.com

Duct seal revolution Realizing windows would be tough to further improve upon, the energy emphasis moved to sealing duct systems through code requirements in the late 1990’s. Where new duct seal codes were adopted, low performance and higher energy consumption problems were quickly noted. Limited studies demonstrated that if ducts were sealed without evaluating existing constraints, air flow performance fell on fractional horsepower motors and energy usage went up significantly with variable speed furnaces and air handlers. Fractional horsepower blowers would slip in the airstream under high static delivering less CFM and more efficient furnaces and air