There! A title like that should get the debate going. And it’s a debate we should be having.

If you’re reading this article in SNIPs Magazine, you are probably involved in the sheet metal business and you likely have an interest in seeing things done right. We have all seen plenty of examples of duct systems that were designed poorly, used poor product selection and were not installed well. 

It’s no surprise to see studies that suggest that faults in the duct system – excessive leakage and pressure drops – could be the largest single preventable energy loss in a building. But most of us should also be able to point to duct systems we have designed, built and installed that were very energy efficient and environmentally conscious. The challenge is getting the bar raised so we are encouraged and rewarded for making the duct systems “green.”

Leadership in Energy and Environmental Design (LEED) was developed by the U.S. Green Building Council (USGBC), beginning in the 1990’s and under constant evolution since. It is the premier green building certification program in the U.S. Many groups, especially governmental, reward projects that have LEED certification. LEED certification plaques are proudly displayed on tens of thousands of buildings in the U.S.

Additionally, having LEED certification can be beneficial to the owners because studies have shown they generally have higher rents and occupancy rates. But LEED has not been above criticism. It is a design tool and looks at energy modeling rather than actual energy performance. 

It operates on a point system that readily awards credit for things like bicycle storage – noble, but not saving the planet as much as turning the lights off when you leave at night. Energy efficiency and reduction is probably the weakest part of their evaluation system – and the hardest to build a case for. So, it’s not surprising that most of the peers I talk with in the ductwork business see LEED as more of a public relations thing – virtue signaling. Especially when we see how better duct systems could have a big impact on the energy it requires to have a comfortable building. 

As ductwork people, we should do something about this. But we have a problem – we are thousands of little voices, not a handful of loud and powerful voices. I’ve spent much of my career focused on spiral duct. A friend of mine did an inquiry about 15 years ago where if you took the combined sales of the five largest spiral duct manufacturers, they only combined to about 7% of the U.S. spiral market.

There are over 2,000 spiral duct machines in the U.S. and Canada. There are tens of thousands of shops that make rectangular duct. We don’t have three or four large industry titans that can carry the ball for all of us. I believe we are unique within the construction industry. 

Take any other trade – like drywall. Thousands of companies install it, but two or three companies make the majority of the sheetrock. The same is true of other components, from floor tiles to lights. Sure, all of us ductwork people buy steel, and our service centers love us. But they have virtually no involvement in “ductwork” and we are just a small percentage of their end users. 

Making LEED Relevant

So what can we do to make LEED real and relevant to us? We can start by getting the message out that when it comes to the environment, we are already some of the good guys. 

Most ductwork is steel, and the steel we use is about 70% recycled content. Our scrap is 100% recyclable, as are our ducts at end of service. Most of our insulations are fiberglass. Other than the small percentage of binder – and we have green versions of those as well. They are comprised of sand (one of the world’s most abundant and renewable resources) and 50% or more are recycled post-consumer glass content. 

Next, we need to take the efficiencies we know there are in better duct systems and make them measurable. We’ve made that harder than it should be --- albeit for some good reasons. A lot of the LEED rating system involves designing a building system against a benchmark. For HVAC systems, that is usually the ASHRAE Standard 90.1 and the ASHRAE Advanced Energy Design Guides. 

Let’s look at duct leakage. Since 2013, the ASHRAE Standard 90.1 has called for duct systems to be constructed to Seal Class A with the expectation, when tested, that the leakage be Class 4 (4 CFM/100 ft.2 at 1” SP). Why do we measure leakage this way? Because it quantifies the skill and effort that went into sealing the duct system. This is important to installers because the amount of ductwork needed to transport air is a matter of the building type and layout, not the amount of air. And the same effort with sealing a duct will show a higher volume of leakage when the pressure increases. 

This method is fair to the contractor. But it doesn’t readily translate to a “percentage of duct leakage” – a number that would let us quantify the energy savings from a tighter duct system. There are some very rough numbers for “expected duct leakage” for round and rectangular ducts at the different Seal Classes (though everything is now supposed to be Seal Class A). We need better numbers, and more categories within Seal Class A. That way, when you test your system for leakage, you can quantify your leakage for the type of duct and method of sealant. That could, in turn, be compared to the “expected leakage” for other types of duct and methods of sealant – and that difference in CFM leakage volume could be converted to an energy savings for possible LEED credits.

The biggest difference we can make is to start sharing the information we have, with the goal of making duct system efficiencies something that can be measured and compared for use in a system like LEED. 

I’ll give you an example. As an installing contractor, how much money would you add to a job if you were going to have to seal to a Leakage Class 3 instead of a Leakage Class 4? Or a Leakage Class 2? I can understand how most contractors would view that as proprietary information they wouldn’t share with their competitors. And it may only be a guess anyway. But the people on the ASHRAE Standard 90.1 committee and other groups that set these benchmarks are not your competitors, and they need credible information for both cost and expected efficiency to make changes or suggestions. 

As a contractor, there is a lot of information you can easily derive – like how many pounds of metal per square foot of building in an elementary school. You can simply look at the last couple of elementary schools you did, total up the metal usage from your shop program and divide by the published square footage of the school. Easy for you, but not readily available to the engineers on the working group that put together the Advanced Energy Design Guide for K-12 Schools. Without this type of information, they can’t set the types of design benchmarks that translate to LEED points for designs and installations that use less material.

The ductwork industry can play a big part in producing “greener” buildings. If we begin to quantify the expected results, we can start to get the attention of groups like the USGBC and their LEED rating program. But without a small group of huge market titans to carry the ball, we need to do this as a bunch of us little guys banding together into committees and working in groups. 

There are a number of groups you can reach out to that would welcome you and put you to work. I am a member of ASHRAE TC5.2, the duct design and construction committee. We are actively looking for more involvement from contractors for their perspective and expertise. We currently have a Task Group focusing on duct leakage. If you would like to volunteer, they can be contacted at Other groups within ASHRAE, as well as other industry groups like SPIDA and SMACNA, are looking to advance the influence sheet metal and ductwork have on the construction industry.

LEED might not make a lot of difference for us right now, and we’re not wrong to feel they are looking in the wrong places for some true energy and environmental impacts. But sheet metal and ductwork can make a difference to the environment – much more than a couple of bicycle lockers or proximity to a commuter train station. It’s going to take some of us in this fractured industry to join together as a larger voice to get the word out: Good ductwork is green.

Reid does business development and engineering for Spiral Pipe of Texas.