Phenolic Duct System Specification
Phenolic is a high performing alternative duct material that helps HVAC Contractors increase the thermal and duct leakage efficiency of their systems. Using pre-insulated phenolic also means that there is no need for separate ductwork and separate insulation as it is a 2-in-1 solution that does the job of both. For both interior and exterior applications, this duct material can offer many benefits for an installation.
For both Engineers and Contractors, phenolic ductwork is an exceptional solution for today's HVAC applications!
Interior ductwork installs are never the easiest part of the job. Between overhead ceilings, tight chases, and finished spaces, it’s where crews lose time, burn labor, and fight material handling. Thermaduct’s InspiralR and Floval systems are built to simplify that part of the job—without changing the way you build duct systems.
These phenolic indoor duct systems help solve problems you deal with every day: weight, access, speed of install, and layout flexibility. Pre-insulated and pre-fabricated, they reduce the number of steps between delivery and final hang, giving your team a cleaner install with less labor and fewer staging headaches.
Installs Faster, With Smaller Crews
InspiralR and Floval are designed to move quickly on site. Pre-insulated and delivered in long sections, they come ready to hang with no field wrapping or separate insulation required. With lightweight panels and simple connection methods, crews can install duct in tight ceilings and crawlspaces without fighting rigid metal sections or custom transitions.
Because most sections are designed and cut before delivery, teams can skip the layout guesswork and move straight to setting duct. Whether you’re working overhead or across finished spaces, fewer moving parts means fewer delays.
Easier on Crews, Especially Overhead
Anyone who's hauled 24" duct overhead knows what it does to your back. Floval and InspiralR systems are built from phenolic insulation—making them a fraction of the weight (over 70% lighter) of traditional metal duct with external wrap. That means easier lifts, safer handling, and less strain on your crew day to day.
The lightweight design also eliminates the need for oversized supports or trapeze hangers. Systems can hang cleanly with minimal supports, making them ideal for ceiling installs or long corridor runs where overhead clearance is tight.
No Special Tools, No Extra Trades
InspiralR and Floval can be installed using common hand tools—no sheet metal brakes, no pin spotters, and no field-fabricated insulation. Everything needed for assembly is included: flanges, sealants, gaskets, or adhesives depending on the system.
For project managers and foremen, this means less dependency on specialized labor. Crews familiar with duct installation can assemble phenolic systems with minimal training (we have a brief online training video) or adding insulators to the job. It’s ductwork—just streamlined.
Sealed from the Start
InspiralR and Floval are designed to meet or exceed SMACNA phenolic duct construction standards, including low-leakage performance for both pressure and return systems. With tight seals at the flanged joints and no exposed liner to fail, airflow stays where it belongs.
That means fewer adjustments during balancing, more predictable system performance, and peace of mind knowing you won’t need to revisit joints that fail under pressure testing.
Ideal for Finished Interiors and Space-Constrained Projects
Floval’s flat oval design is ideal for corridors, drop ceilings, or tight plenum spaces where rectangular duct doesn’t fit and spiral might hang too low. InspiralR is well suited for straight runs and vertical drops that benefit from a round form with cleaner airflow.
Both systems are built for low-profile installs—pre-insulated, clean-looking, and field paintable for retrofits, schools, hospitals, and interior renovations. No wrap, no mess, and less disruption to building occupants.
Download our Guide Specification to see how your application can use InspiralR & Floval
The Advantages of Using InspiralR and Floval For Your Application
InspiralR and Floval are pre-insulated, high efficiency spiral and flat oval duct systems that give you increased performance of round ductwork. These patent pending systems provide thermally efficient and low leakage ductwork packaged in an extremely lightweight and high quality closed cell phenolic insulation. There's no need to insulate separately as all InspiralR and Floval Ductwork reach a minimum of R-6 insulated value!
R-6 Phenolic Insulated Values
Phenolic has an excellent thermal performance with some of the best R- values per inch of insulation available on the market .This superior insulating efficiency means that the required R-value can be achieved with thinner insulation that are highly resistant to heat transfer. This results in reduced energy consumption and lower operating costs for your applications. With the increasing pressure of energy codes always moving towards more insulation, Phenolic duct systems provide solutions that don’t only meet today’s code requirements but those of the future too.
All InspiralR and Floval ductwork come pre-assembled and ready to install at an R-6 insulated value. These systems are UL 181 rated for 10" positive and 8" negative pressures. The aluminum phenolic panel interior provides an interior free of loose fibers that will not support mold growth. InspiralR and Floval are designed to provide customers with extremely low air leakage. Increase your customer's HVAC system efficiency and reduce long term energy costs.
Included Connection Materials
No need to pay extra to install your ductwork, as InspiralR and Floval come with pre-installed flange connections and drawbands to install a near airtight connection. These will feel very familiar to anyone who has installed flanged spiral ductwork or double wall insulated spiral with flanges.
Pre-Insulated phenolic ductwork assembled and installed in line with the SMACNA Phenolic Duct Construction Standards can easily achieve anything between a SMACNA Class 1 and SMACNA Class 3 leakage rating. The long term benefits of this lower air leakage can include reduced runtime on HVAC equipment over the life of the system therefore bigger energy savings, better Indoor air quality with phenolic’s smooth aluminum interior and improved comfort.
Lightweight Ductwork
InspiralR and Floval can weigh a fraction of traditional double wall spiral or flat oval ductwork. This can significantly lower the impact ductwork will have on a building and reduce weight hanging above building occupant's heads.
Ductwork made out of rigid phenolic foam can provide significant weight savings on your project. Indoor systems offer the highest savings, with rectangular, round and flat oval systems all capable of providing over a 70% reduction in weight compared with sheet metal wrapped in fiberglass.
Ease of Installation
InspiralR and Floval go together quickly and will be familiar to HVAC contractors. Have a virtually airtight connection in under a minute! Pairing that with the reduction in weight and your time in the field will be minimized with our pre-insulated ductwork systems!
See our installation training site for a full walkthrough on how to install InspiralR and Floval.
Space Saving
Phenolic ductwork is pre-insulated, which means it does not require any additional insulation wrapping. Because of this, space requirements are minimal and duct can be installed in tighter places, including flush to ceilings and walls to free up more space where every square inch matters. You may also need fewer hangers to contend with depending on the size of the ductwork.
InspiralR and Floval's standard connection drawbands also can serve as a hanging point for this lightweight ductwork system. Tight on ceiling space? Floval is your solution for areas where applications may not allow enough space to wrap ductwork.
third party tested and backed by a 10 Year Limited Warranty
Some Phenolic Ductwork systems have gone through extensive UL testing to achieve a UL 181 Listed status, starting back in 2004. This is an extensive and rigorous series of tests and ongoing inspections that covers many aspects of safety and product durability - structural testing, pressure testing, mold and bacteria growth, static load and flame and smoke spread, among others.
InspiralR and Floval are built to last and are proudly backed by a 10 year limited warranty. Installers can find our registration process by going through our installation training course.
Designed to Meet Engineers Specifications, Built Around the Way Contractors Work,
Thermaduct’s phenolic systems don’t ask you to change the way you install ductwork—they just remove the extra steps. You’ll still hang, seal, and support ductwork like you’re used to—but faster, with less labor and less cleanup.
If your current installs are slowed down by field wrapping, overhead lifting, or tight layouts, InspiralR and Floval give your crews a better way forward, without cutting corners.
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Phenolic is a high performing alternative duct material that helps HVAC Contractors increase the thermal and duct leakage efficiency of their systems. Whether you're looking for indoor or outdoor solutions, learn more about how phenolic systems can benefit your application!