Building engineers and mechanical contractors may want take note: This is the year that duct design and installation will begin to face an increased amount of scrutiny.
A slew of tighter, more encompassing standards and regulatory guidelines targeting ductwork are on the way — or have already arrived. Given the unprecedented attention that these regulatory updates are now giving to total system performance, 2018 could go down in building history as the Year of the Duct.
“When it comes to ductwork, there has been a long-standing chasm between best practices and cost-cutting measures,” said Ken Mueller, a ductwork fabrication specialist at Cincinnati-based HVAC contractor DeBra-Kuempel. “I’ve found that unless there is a specific performance goal being targeted or mandatory proof of compliance, attention to proper duct functioning is often lax.”
As a result, building performance suffers. Studies from the U.S. Department of Energy, the Environmental Protection Agency and others, make clear that leaky, improperly installed ductwork is often the No. 1 culprit behind poor indoor air quality, ineffective HVAC function and energy inefficiency.
With growing attention being given to improving building performance, many regulatory agencies are now responding.
Toward the end of 2013, the Energy Department’s Federal Energy Management Program compiled a list of recommended strategies for commercial and industrial building owners looking to save energy. Included for the first time in the top three HVAC-related recommendations was the use of aerosol-based duct sealant. Three years later, the EPA announced a significant shift in its Energy Star program with new emphasis being placed on a “total system” approach to energy efficiency. The Energy Star-Verified HVAC Installation program requires a comprehensive review of the total HVAC system with particular attention being given to duct tightness.
These and other precursor programs provided a glimpse of what regulatory committees were preparing behind the scenes. Now, after working their way through committees and approval processes that include considerable feedback from the contractor community, a score of new updates focused on tightening duct standards and more rigorous duct testing has arrived. Here are a few examples.
ASHRAE standard update
The latest version of ASHRAE Standard 189.1, “Standard for the Design of High-Performance Green Buildings,” is slated for official release this year. Updates to this standard will expand duct testing requirements to include, for the first time, medium-pressure ducts as well as high-pressure ducts.
“I spearheaded this update to reflect the expanded use of lower pressure ductwork and the industry’s growing understanding of the performance hit that duct leakage — even in low-pressure ducts — can have on energy usage, indoor air quality and other building performance issues,” said Jeff Boldt, a voting member of the standard’s committee and director of engineering at IMEG Corp.
Bob Reid, the former chairman of an ASHRAE technical committee and currently with Spiral Pipe of Texas, said the testing requirements are a major change.
“The industry has resisted testing because of the additional costs involved,” Reid said. “But new options now make sealing existing ductwork cost effective, so in reality, building owners can either make a relatively small payment upfront to ensure their ducts are operating properly, or they can continue to pay higher operating costs throughout the life of the building.”
The most recent updates to the ASHRAE Handbook include expanded parameters for duct testing. According to this widely adopted manual, industry standard practice now dictates that the supply air, return air and exhaust-air systems be tested for leakage during construction and then after the duct system is fully assembled and installed.
Duct sealing is now being incorporated into more building codes. Picture courtesy of Aeroseal.
The new guidelines recommend that 25 percent of the system be tested during construction and another 25 percent if any of the initial sections fail. It then dictates that all of the system be tested if the system fails to meet acceptable leakage rates after the second testing. According to the handbook, leakage tests should be conducted by an independent contractor.
Additionally, the handbook is now recommending a maximum fractional leakage for fan systems of 5 percent. The “system” includes ductwork upstream and downstream of the fan as well as components mounted to that ductwork where leaks can occur (dampers, variable-air-volume boxes, etc.). Assuming an average air device leakage rate of 2 percent leaves contractors with very little room for duct leakage (2 or 3 percent), making duct sealing even more critical to meeting the requirement.
The latest version of the International Energy Conservation Code took effect Jan. 1. Among changes in the code is a provision that requires building owners to provide all HVAC equipment and testing data needed to determine proper installation. This is intended to increase post-installation testing and drive processes that ensure effective duct sealing has been accomplished.
Uniform Mechanical Code
Developed by the International Association of Plumbing and Mechanical Officials, the Uniform Mechanical Code is an American National Standards Institute-approved code used to govern the installation, inspection and maintenance of HVAC systems. The recently updated code includes, for the first time, guidelines regarding the testing of ductwork that embraces a stepped approach, with an initial testing of 10 percent of the ductwork. If this sample fails to pass, it’s recommended that subsequent testing include an increasingly larger testing sample.
In addition to these updates, the building industry is poised for other revisions affecting the performance and testing of duct systems. Among those scheduled:
Expected in early 2018, this fourth version of the Sheet Metal and Air-Conditioning Contractors’ National Association’s HVAC Duct Construction Standards manual reflects industry innovations that impact the construction, installation and repair of HVAC ductwork — both metal and flexible ducts.
A new industry guideline, “Method of Test to Determine Leakage of Operating HVAC Air Distribution Systems,” is expected to recommend specific methods for duct testing.
California Title 24
Often used as the blueprint for many other state building code standards, the latest version of California’s building standards code is expected to include new emphasis on reducing duct leakage and the role effective duct performance plays in the energy efficiency of today’s commercial buildings. With the latest updates to this standard currently in the review and comments stage, these changes are expected to go into effect in early 2020.
These standards all stress that proper duct installation and maintenance is critical to overall building performance. Still, the latest reports highlight the fact that a large percentage of residential and commercial buildings across the U.S. continue to be constructed and renovated with little to no attention being paid to proper duct functioning. A 2016 survey conducted by the Building Commissioning Association found that 74 percent of building professionals polled believe most buildings in the U.S. today have significant duct leakage. More than 65 percent of respondents believe that leakage rates of 15 percent or more are common or highly likely.
“For decades now, the industry has been well aware of the size and scope of the problems associated with leaky and underperforming ductwork, said Neal Walsh, a senior vice president at Aeroseal LLC, which makes duct sealing equipment. “Now that there are finally practical, cost-effective ways to fix this critical issue, industry standards bodies are taking notice. As a result, 2018 will certainly prove to be the Year of the Duct.”
This article was supplied by Aeroseal.