Environmentally Friendly Ducting for HVAC Systems Are SPOT Products Green?
The short answer is “YES!” The slightly-less-short answer is: “If you are not using spiral ducts from Spiral Pipe of Texas, then you aren’t really green at all.” Of course, a provocative response like that deserves some elaboration. We are happy to provide it. For the last 20 years it has become fashionable for companies to describe themselves as “green”, and we see plenty of advertising for construction components festooned with leaves. Our term for this is “green-washing”. To be fair, if you have a product where environmental consciousness was not previously a concern, it is a good idea to find out what is “green” about your product, try and do better, and reassure consumers that you care. Spiral duct has always been green –– long before the term came into being.
The spiral duct industry started in Northern Europe at the end of World War II. As economies recovered, new and better buildings were incorporating ventilation and conditioning systems that had been developed during the previous few decades. They had three problems – energy was expensive, raw materials were also expensive and often in short supply, and there was a shortage of skilled labor with so many young men lost in the war. To solve all three problems, spiral ducts were developed. Round is the most efficient shape for transporting air. It has lower pressure drops, saving fan horsepower, and there is less heat gain/loss through the surface than with rectangular shapes.
Round is also the strongest shape for transporting air. Limit surface deflection to prevent metal fatigue and duct rumble, and metal thickness and additional reinforcement were the ways of accomplishing this with traditional rectangular ducts. Round ducts have virtually no wall deflection in normal operating conditions, and the helical spiral seams strengthen the duct even more.
As a result, spiral duct systems usually weigh 30% less than equivalent rectangular duct systems –– less material! Spiral ducts are normally produced in longer lengths than rectangular ducts. Where rectangular duct is normally provided in 4- or 5-foot nominal lengths, the standard for spiral duct is 10 feet with lengths as much as 20 feet commonly provided. It’s no surprise that most estimators predict installation rates of 50% more pounds per man-hour installed for round spiral duct than for rectangular duct. Don’t forget that we’re talking about a product that generally has 30% less pounds to start.
Here we have a product –– spiral duct –– that uses less energy, less material and less labor than other methods of transporting air. By anyone’s definition, this is an inherently “green” product. Let’s take this a few steps further. Most spiral duct systems produced at Spiral Pipe of Texas are galvanized steel and where insulation is required, fiberglass insulation is used. Galvanized steel is one of the most recycled materials on the planet. Approximately 70% of all steel and 30% of all zinc consumed are made of recycled material. At the end of service, virtually 100% of galvanized steel ductwork can be recycled. For our insulated products, our standard for double-wall products is Knauf Friendly-Feel Duct Wrap or an equivalent product.
The Knauf product contains three primary ingredients: 1) sand –– one of the world’s most abundant and renewable resources; 2) a minimum 50% recycled post-consumer glass content; 3) a new binder technology that reduces binder embodied energy by up to 70% and features bio-based materials rather than non-renewable petroleum-based chemicals traditionally used. They contain no phenol, formaldehyde, acrylics, or artificial colors.
Spiral duct is a “green” product made from “green” materials. Let’s look further at some of the regulations and compliance standards we work under. Most states, including our home state of Texas, have adopted state-wide energy codes. In Texas, we use the ANSI/ASHRAE/IES Standard 90.1–2013 “Energy Standard for Buildings Except Low-Rise Residential Buildings”. It calls for ductwork to be constructed to Seal Class A. Part of the requirement involves the contractor assembling our ducts using sealant, but our duct components themselves meet Seal Class A.
The only mechanical seams that do not have to be sealed under this standard are the spiral lock seams of spiral duct. They have been proven to have almost no inherent leakage. Per this standard, all ducts should be constructed and installed to meet a Duct Leakage Class 4, regardless of whether testing is required or not. According to the ANSI/SMACNA HVAC Air Duct Leakage Test Manual-2011, the expected leakage performance of a round or flat oval spiral duct system, assembled to a Seal Class A, is a Duct Leakage Class 2. Our products greatly outperform the energy codes with only half the leakage that is allowed.
We take duct leakage seriously, because it’s considered to be the single largest preventable energy waste in commercial and residential buildings – even more of a waste than leaving lights and A/C on when the building is unoccupied. To go further, ASHRAE is producing a series of Advanced Energy Design Guides for commercial construction. These are guides for achieving progressive amounts of energy savings toward a net zero energy building and are available for different building types.
Their recommendation for Ductwork Design and Construction is:
“Low-energy use ductwork design involves short, direct and low pressure drop runs. The number of fittings should be minimized and should be designed with the least amount of turbulence produced…. Round duct is preferred over rectangular duct. However, space (height) restrictions may require flat oval duct to achieve the low turbulence qualities of round ductwork.”
We know from ASHRAE and SMACNA that round, flat oval, and spiral duct is the way to go for efficiency and low leakage. Additionally, ASHRAE publishes a Duct Fitting Database that includes dynamic efficiency data for all duct and fitting configurations. Using it, you can see the actual performance efficiencies of round and flat oval spiral ducts and fittings over equivalent rectangular ducts. These lower pressure drops optimize the duct system performance and allow the transport of air at lower fan horsepower. With less inherent leakage, you won’t need to produce as much air.
Which brings us to the question of “LEED”. Leadership in Energy and Environmental Design (LEED) is one of the most popular green building certification programs used worldwide. It is an important first step in promoting “green” construction in commercial buildings. In a perfect world (at least for us) the LEED guideline would simply state “Use round and flat oval spiral ducts and fittings from Spiral Pipe of Texas –– and here’s your points!” Unfortunately, it’s not that simple. Many of the “green” features of our products are not even things you can earn LEED credits. They actually are “prerequisites” –– preliminary requirements to get any level of LEED certification.
- “EA Prerequisite: Minimum Energy Performance Required” –– Option 1 –– states that you must demonstrate an improvement of 5% in a proposed building rating compared to ANSI/ASHRAE/IES Standard 90.1-2010. That standard calls for all ducts to meet Seal Class A and Leakage Class 6. Remember, we meet the 2013 version of Standard 90.1 with a Leakage Class 4 and an expected performance for round and flat oval spiral ducts of a Leakage Class 2. Option 2 – is to comply with both the ANSI/ASHRAE/IES Standard 90.1-2010 and the ASHRAE 50% Advanced Energy Design Guide. Once again, that’s round and flat oval spiral ducts and fittings.
- “MR Prerequisite: Construction and Demolition Waste Management Planning Required” –– As stated above, our ducts are virtually 100% recyclable, so any excess, waste, or demolished product should not end up in a landfill.
- “EQ Prerequisite: Minimum Acoustic Performance Required” –– applies to schools and a maximum background noise level of 40 dBA from HVAC systems must be achieved. Our round and flat oval products outperform metal rectangular and non- metal ducts in true sound attenuation. With less or no flat surfaces, additional airflow-induced noise from “oil-canning” is eliminated. Turbulence is the main source of airflow generated noise, and our lack of square corners eliminates much of the airflow turbulence.
Spiral duct uses less energy, less material, and less labor than other methods of transporting air.
This does not mean you can’t get “LEED points” for using spiral duct and fittings. You just might have to do a bit more work. The following are potential sources for LEED credit:
- “EA Credit: Optimize Energy Performance” –– you can get as many as 18-20 points on a project for achieving higher levels of energy performance beyond the prerequisite standards. Lower leakage and higher efficiency than the Standard 90.1-2010 baseline will result in lower fan horsepower, as well as less demand on chillers and boilers. There are energy simulation programs available where such savings can be translated into percentage improvement in energy performance, and from there to LEED “points”.
- “MR Credit: Building Product Disclosure and Optimization –– Sourcing of Raw Materials: Option 2. Leadership Extraction Practices” –– we can contribute, along with other materials used in the building, to the 1 point which can be awarded in terms of the recycled content of our products.
- “MR Credit: Construction and Demolition Waste Management –– Option 2. Reduction of Total Waste Material” –– we can also be a contributor to the available 2 points. For this credit, you must not generate more than 2.5 pounds of construction waste per square foot of the building’s floor area. At Spiral Pipe of Texas, our standard practice is to coordinate the project with our customers and produce product and quantities matching our Coordinated Assembly Drawings. We can’t speak for the rest of the products on the jobsite, but there should be no construction waste from our products.
- “EQ Credit: Low-Emitting Materials” –– can give 1-3 points for reducing concentrations of chemical contaminants. One of the categories is “interior adhesives and sealants applied on site”. You certainly need to seal the ducts to meet the above requirements. Using a duct system from Spiral Pipe of Texas can reduce or eliminate much of the on-site use of sealants. Our Triple-Rib gasketed duct system allows you to install sealed ducts without site-applied duct sealants. Even when sealants are used, round and flat oval spiral duct systems typically use far less sealants than rectangular systems. There is no longitudinal seam to be sealed since the spiral lockseams are exempted from sealing. Round and flat oval ducts have smaller perimeters than equivalent rectangular ducts, so there is less transverse sealing. Longer lengths of spiral duct results in less transverse joints to seal in the first place. The traditional slip-fit joints in spiral pipe require less volume of sealant per length of seam than required for most rectangular joint types.
- “EQ Credit: Construction Indoor Air Quality Management Plan” –– has an available 1 point to which we can contribute. One requirement is to protect absorptive materials stored on-site and installed from moisture damage. We offer shipment of our products using the SPOT DuctShield plastic film protection installed on all open ends.
- “EQ Credit: Acoustic Performance” –– has 1-2 points available for reducing HVAC background noise and sound transmission. Round and flat oval ducts have less airflow generated noise than rectangular ducts, and our double-wall and insulated products increase actual sound attenuation through a duct path.
- “IN Credit: Innovation” –– has 1-5 points available “to encourage projects to achieve exceptional or innovative performance”. Even though round and flat oval ducts are known to be more efficient than rectangular ducts, as well as usually less expensive, quieter, and less total material weight, we still see about 70% of commercial duct systems designed primarily with rectangular duct. True innovation would be to reverse that trend by designing highly efficient round and flat oval ducts from Spiral Pipe of Texas.
We hope this answers the question “Are Your Products Green?” Spiral Pipe of Texas is proud to make products that are “green” throughout their history and origin, in their manufacture, and through their use.
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Spiral Pipe of Texas (SPOT) fabricates high quality, MADE IN THE USA sheet metal products for the heating, air conditioning and ventilation (HVAC) industries.
