PVC Pipes & PVC Duct Fittings for HVAC Systems

Polyvinyl chloride (PVC) pipes and PVC duct fittings are excellent for heating, ventilation and air-conditioning (HVAC) ducting applications. PVC is lightweight, durable, flexible, non-toxic and generally inert and non-reactive. PVC pipes are available in longer lengths (and may be ordered in custom lengths), minimizing the number of joints required. The availability of various PVC duct pipe fittings also allows for a lot of latitude in piping system design.

However, can you use PVC pipes and PVC duct fittings in HVAC systems? If yes, what characteristics make PVC a good material for HVAC ducting, and how and where can you use it? When should you refrain from using PVC duct pipes in HVAC systems?

We’ll try to answer all these and more, based on our years of experience in the field. So sit back, relax and read on to learn why and when you should consider using PVC pipes and PVC pipe fittings in HVAC applications.

Can you use PVC pipes for air-conditioning?

Yes, you can use PVC pipes and PVC duct fittings in air-conditioning systems. In fact, you can also use them for heating and ventilation. The following characteristics of PVC pipes and fittings make them particularly suitable for HVAC ducting systems:

• Smooth interior wall: PVC pipes and pipe fittings made of PVC have smooth inner walls. This translates to reduced friction that can inhibit or resist airflow. Consequently, the hot or cold air can flow smoothly and efficiently through the ductwork.
• Low thermal conductivity: PVC has a thermal conductivity of 0.19 watts per meter Kelvin, which is lower than the thermal conductivity of other piping materials such as carbon steel (54 W/mK) and copper (401 W/mK). Chlorinated PVC (CPVC) or PVC that has undergone chlorination has an even lower thermal conductivity at 0.14 W/mK.
• Corrosion resistance: In commercial buildings, humidity, fumes and exhaust gasses can accelerate corrosion in metal pipes. PVC pipes make great ductwork material because of PVC’s excellent corrosion resistance. PVC ductwork is especially recommended for HVAC ducting that will be installed beneath the floors because they’re not susceptible to moisture-induced corrosion.
• Versatility and flexibility: The availability of many types of PVC duct fittings means PVC pipes can be joined in many ways and support various design configurations.

Can PVC pipes be used for HVAC ductwork?

Yes, you can use PVC pipes instead of galvanized steel or aluminum in HVAC ductwork. Ductwork refers to the system of ducts or pipes that transports air-conditioned or warm air from the heating or air-conditioning unit to specific rooms in your home.

Air-Conditioning Ductwork

PVC pipes are an excellent material for air-conditioning ductwork. Their low thermal conductivity means they can efficiently carry cool air through your house. Their smooth interior walls reduce friction loss, further enhancing their efficiency in conditioned or heated air transport.

These characteristics make PVC pipes an excellent option when you need to install extensive ductwork to cool or heat a big home or building. Add a little insulation, and your PVC ductwork should be able to transport cold air with little to no heat gain.

Heating Ductwork

PVC pipes and PVC duct fittings can be used in heating ductwork, too. You should have no issues if you maintain your heating equipment temperature at the U.S. Department of Energy-recommended thermostat setting of 68-70°F during winter.

When not to use PVC for HVAC ductwork

There are two instances when you should consider alternatives to PVC ductwork: if you plan to heat your home at much higher temperatures than recommended and if your ductwork design cannot accommodate the weight of plastic pipes.

1. Heating Requirements

If you like your home extra toasty during winter, ask your contractor if PVC is still suitable for use in your HVAC ductwork. Under normal conditions, 140°F is the maximum operating temperature of PVC pipes. It’s 100°F under pressure. Chlorinated PVC (CPVC) or PVC that has undergone an extra chlorination process has a somewhat higher maximum operating temperature of 180°F with or without pressure.

When you breach a PVC duct pipe’s maximum operating temperature, the plastic pipe will soften and lose its shape and structure. Therefore, you must consider temperature constraints when considering PVC ductwork for heating.

In other words, if your heating system will transport air at temperatures well below the PVC pipe’s maximum operating temperature, you may use PVC pipes in your HVAC ductwork. Otherwise, consider using a different material.

2. Ductwork Design Considerations

PVC is a lightweight material. However, PVC ductwork can be twice as heavy as metal ductwork. Therefore, if you’re installing a PVC ductwork system, make sure your engineer has accounted for the weight of the ductwork in your HVAC system design.

Additionally, the weight of the HVAC system adds to the structural load of a building. Your engineer must assess whether your home can carry the dead load of your HVAC system, including your PVC ducts, duct fittings, insulation (if using), and duct supports.

Structural adjustments and retrofitting may have to be made. Alternatively, your HVAC system design may have to be modified. For instance, you may need to install your PVC ductwork behind the walls or underneath the floors instead of anchoring your PVC ducts to the ceiling.

How else can you use PVC pipes in HVAC systems?

Aside from their role as HVAC ducts, PVC pipes may also be used as drain lines, flexible ducts and ventilation pipes.

• HVAC drain lines: Air-conditioning systems draw out heat and moisture, which turn into condensation that the HVAC system needs to release. PVC pipes are an excellent material for HVAC drainage. They can serve as the drain lines that carry the condensation from the inside to the outside of the home.
• Flexible ducts: Flexible PVC ducts can connect HVAC equipment, grilles and vents to rigid PVC ductwork.
• Ventilation pipes: PVC pipes can be used in active and passive ventilation systems (e.g., Venturi tubes) that allow fresh air in and flush warm air out.

What type of fittings are used with PVC pipes in HVAC systems?

PVC pipes are excellent for HVAC systems because of the variety of PVC pipe accessories and fittings you can use in your PVC ductwork design. The following are some of the most common PVC duct accessories and fittings:

• Couplings: PVC couplings connect two pipes. There are many types of PVC couplings, including double-bell couplers.
• Tees: Tees are T-shaped fittings with three ends that converge to merge three pipes.
• Crosses: Crosses are cross-shaped fittings that can join four pipes.
• Bell mouth: Bell mouths are used at the inlet or outlet end of a PVC duct or pipe.
• Bends: PVC pipe bends are affixed to PVC ducts to change the direction of a pipeline. Variants include streetlight bends and long-radius bends.
• Elbows: PVC elbows allow PVC ducts to turn by 90 or 45 degrees. PVC bends and elbows essentially serve the same function, but they differ in their radius of curvature.
• End caps: PVC end caps seal the ends of PVC pipes.
• Plugs: PVC plugs, designed to sit inside fittings, interrupt the flow of fluid in pipelines.
• Adapters, reducers and bushings: Adapters, reducers and bushings make it possible to connect different types and sizes of PVC pipes.
• Flanges: Flanges are disc-like fittings that allow you to create a tight seal between a pipeline and an accessory. Puddle flanges, commonly used to seal wall pipe openings, are examples of flanges.
• Nipples: Nipples may be used to connect PVC ducts with boxes, fittings and enclosures.

PVC ducts and fittings for HVAC systems

PVC is an excellent material for HVAC piping. You can create PVC ductwork to transport cool or heated air throughout your home. You can also use PVC pipes and fittings in active and passive ventilation systems. PVC pipes also work as drain lines and flex ducts.

Polyfab Plastic Industry LLC manufactures high-quality PVC and HDPE pipes for above-ground and underground installation and are suitable for use in various industries. Contact us to inquire about PVC ducts and fittings that can be used in residential, commercial and industrial HVAC systems.