When commercial ductwork is considered energy inefficient, it typically results from innate thermal loss and airflow restriction. These problems occur during the installation process when installation teams don't properly insulate or measure ducts, specifcally in shape and diameter.
Proper ductwork design avoids this duo of year-round heating and cooling issues. When installing commercial ductwork for a new building, consider the following to save time and energy for the building -- and your installation team:
Start with a great ductwork design. It’s harder to make commercial HVAC more energy efficient when it has an existing, subpar ductwork system. You can share actionable tips with the building owner, like close the blinds or use fans when it's warm outside.
However, to truly have an energy efficient system, you need to start from the ground up -- literally. A great ductwork design should take into consideration the following qualities:
- Proper duct sizing
- Solid connections
- Uncompressed ductwork
- Properly supported bends
- No sagging
If the ductwork design doesn’t have these basic qualities, energy efficiency is at risk. The lack of consideration in design can also pull in unfiltered outside air, causing the building’s occupants to breathe in unwanted particles like fiberglass strands, dirt, and/or radon gas. This can lead to unwanted sickness and out-of-season allergy stimulation.
Consider flexible ducts. Flexible ducts work best for attaching supply air outlets to more rigid ductwork made from sheet metal. They're commonly attached with long zip ties or metal band clamps for sound structure.
While it’s inadvisable to make an entire HVAC system from flex duct, the material has gained notoriety for its energy efficient benefits.
Made from PVC, rubber, stainless steel, silicone, polyurethane, or neoprene-dipped polyester fabric, flex ducts must be fully extended to stay energy efficient. Only the minimum length necessary for connections should be used, according to Jeff Elzinga of Hart & Cooley, Inc. in Grand Rapids, Michigan.
Rex Anderson of Goodman Global, Inc. in Houston, Texas, suggests using a higher R-value if you choose to install flex duct. The R-value assesses the resistance to heat flow through a given thickness of material. In theory, the higher the R-value, the greater that resistance.
Anderson’s advice is use an R-8 value for higher energy efficiency and to follow the manufacturer’s guidelines very closely.
Or fiberglass duct board. “Fiberglass duct board systems...deliver virtually leak-free performance when fabricated and installed properly,” Stevie Jones of Gemini Connections and North American Insulation Manufacturers Association, said to ACHR News.
“By doing so, [you] reduce the HVAC system operating costs by controlling heat loss or gain through the joints and duct walls.”
The single-component system offers thermal and acoustical insulation (one of the main culprits to energy inefficiency), airtight performance, smoother turns, and factory-controlled insulation thickness that ensures specified R-values are met in a single product.
“Closures made with...listed pressure-sensitive tape, heat-activated tape, or glass fabric and mastic save energy by virtually eliminating air leakage," Jones said. "And they are code compliant.”
Seal the ductwork. While commercial ductwork doesn’t have moving components like other HVAC appliances, it still undergoes stress and static pressure. To avoid failing ductwork due to natural wear and tear, seal it with materials recommended by the Air Conditioning Contractors of America.
Once you’ve sealed the commercial ductwork, test it. The quality of a proper insulation largely benefits the long-term energy efficiency of the building.
The fundamentals of duct sizing and installation with special consideration for materials should lead to a proper, energy efficient ductwork design in any commercial building.
For more information on how to be energy efficient in installation, please click on the button below to download Kaempf & Harris’ Ultimate Guide To Commercial Ductwork: