Thermaflex
Thermaflex Flex-Vent KM Insulated Flexible Duct
Best insulated ducting for efficient residential and commercial HVAC system installations.
Equip your air distribution system with this Thermaflex Flex-Vent KM insulated duct! This flexible unit is designed for use in low- to medium-pressure cooling and heating HVAC systems. It can be used in both supply and return sections, and it allows you to resolve issues with misalignment between system components and with ducts installed around obstacles. It is also ideal for making system extensions and changing conditioned zones in new or retrofit applications. This efficient unit is composed of a smooth liner, thermal insulation, a tough outer vapor barrier, and a double air seal. The inner core is formed of laminated, strong polyester film that encapsulates a heavy, corrosion-resistant steel wire helix. It is fully lined with a thick blanket of EcoTouch formaldehyde-free fiberglass insulation for efficient air delivery. The outer vapor barrier features a jacket of fiberglass scrim reinforced with metallized film laminate, and it will not unravel. This unit is quick and easy to install, and it is a cost-effective alternative to fabricated and fitted ducts. It is made with natural materials and a high level of recycled content. It boasts an impressive R-8 thermal application value to prevent heat from entering or escaping your ducts, and it has an internal operating temperature range of -20 to 250 degrees Fahrenheit. It meets UL 181 and CUL S110 requirements and NFPA 90A and 90B standards. This product is made in the USA and features recycled content.
$208.49
Owner Satisfaction
4.5
/ 5
Category Rank
181
/ 675
#181 in Furnace & Boiler Accessories
Price vs Category Average
+4%
Above average
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Who it's for
- Homeowners looking to lower monthly energy bills
- Contractors working in tight or complex crawl spaces
- Families wanting a quieter and more peaceful home environment
Who should skip it
- DIY installers lacking experience with delicate duct routing
- Allergy sufferers requiring pristine and easy-to-clean air ducts
- Property owners prioritizing long-term, maintenance-free infrastructure
Performance breakdown
Thermal Efficiency
The R-8 rating provides superior insulation for consistent temperature control.
Installation Flexibility
Easily navigates tight spaces and complex system misalignments.
Durability
Corrosion-resistant steel helix ensures long-term structural integrity.
Airflow Performance
Smooth inner liner minimizes friction for efficient air delivery.
Environmental Compliance
Formaldehyde-free insulation and recycled materials meet high sustainability standards.
Safety Standards
Fully certified to meet rigorous UL and NFPA safety requirements.
Key Specs
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1/Each
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28 lb.
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25 Feet
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14 Inches
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Silver
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Corrosion-Resistant, Made in America, Recycled Content
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Fiberglass, Polyester, Steel Wire
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Insulated, Flexible Ducts
Features
- Corrosion-Resistant
- Made in America
- Recycled Content
- R-8 thermal application value
- Formaldehyde-free fiberglass insulation
- GreenGuard Gold certified
What customers say
Thermaflex Flex-Vent KM Insulated Flexible Duct is highly regarded for its exceptional quality and ease of installation. Users consistently report excellent thermal performance, leading to improved energy efficiency and fewer condensation problems. Its remarkable flexibility simplifies installation in challenging spaces, saving significant labor time compared to rigid options. The durable outer jacket withstands handling and installation stresses, ensuring long-term reliability. While the inner core requires careful handling during installation, the overall consensus is that the superior quality, longevity, and certified performance justify the investment. This duct is a top-tier choice for demanding HVAC applications.
Know before you buy
Yes, the Flex-Vent KM is designed for both supply and return sections in low- to medium-pressure HVAC systems, making it suitable for both heating and cooling applications.
This duct features an R-8 thermal application value. This high level of insulation helps prevent significant heat gain or loss as air travels through the duct, which improves your system's overall energy efficiency.
Yes, the product is GreenGuard Gold certified and uses formaldehyde-free fiberglass insulation, ensuring it meets strict standards for low chemical emissions in indoor environments.
The internal operating temperature range for this duct is between -20 and 250 degrees Fahrenheit, allowing it to handle standard residential and light commercial HVAC temperature fluctuations.
No, the outer vapor barrier is constructed from fiberglass scrim reinforced with metallized film laminate, which is specifically designed to prevent unraveling during installation.
Yes, the Thermaflex Flex-Vent KM meets UL 181 and CUL S110 requirements, as well as NFPA 90A and 90B standards for fire safety and duct performance.
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$208