FRP Duct Specifications


Various shapes of FRPRound, rectangular, and oval are the typical filament wound construction shapes. Upon request, shapes such as triangular and others are available.  Qualified Monoxivent staff are available for designing projects requiring non-standard construction.


Duct diameters are available from 2-inch through 14-feet, and rectangular sizes as required for your projects. Monoxivent’s 824-API pre-insulated double wall duct is also available in the above ranges.

Wall Thickness

Wall thicknesses are based on ASTM and SMACNA standards at a minimum. Additional wall thicknesses can be designed into any project. 


Standard fittings included: Elbows, Tees, Laterals, Y’s, Reducers, Dampers, Registers, Boxes, Square-to-Rounds, Crosses, Flanges.


A  range of colors is available for overhead exposed applications.  Please contact Monoxivent for charts.

Single Wall (any configuration available)

Single Wall or Double Wall UnderDuctOur Class 1 rated single wall duct, meets 25/50 flame/smoke requirements of UL 181.  Monoxivent UnderDuct 824 Low Smoke has been accepted for HVAC and occupied Industrial areas. It is an excellent choice for corrosive environments where flame and smoke development are a concern, such as laboratories and swimming pools.

Double Wall (any configuration available)

Double wall Monoxivent UnderDuct will eliminate any thermal losses and save time and money compared to insulating on site. When supplied with the standard 1” insulation, the duct has a k factor of 0.16 and an R value of 6. Also available in R-10, R-14 by request.

FRP Fitting and Joints

Monoxivent FRP offers a complete line of fiberglass fittings to complete your FRP Duct system.  These quality fittings made from fiberglass composite materials are designed and manufactured to the highest standards.  Field joints within the corrosion resistant product line are made using the wet lay-up method using a glass, resin wrap (see below).

Underduct Production Process

Monoxivent’s manufacturing source has over 50 years of experience and is a leader in the Underslab Fiberglass Ductwork market.  Monoxivent has a nation-wide network of sales representatives and a top-tier inside support crew, which provides engineering, design, sales, service, and marketing.  UnderDuct is offered both as single wall and pre-insulated double wall duct to meet any ventilation needs.  Monoxivent 824 Low Smoke Class 1 duct is recommended for direct burial.

Monoxivent 824 SDS