Should PEX Piping Be Insulated?

PEX piping is used in nearly all new home construction and plumbing pipe replacements done today. Insurance companies report that over 250 million homeowners annually have property damage from busted water pipes, many caused by freezing temperatures.

PEX has become the piping of choice by plumbers because the piping polymers allow it to flex, making installation much easier. PEX is lightweight and can bend, reducing the number of connection joints. Many debates that because the piping has flexing properties, it doesn’t need insulating. Does PEX piping need to be insulated?

PEX piping exposed outdoors or inside uninsulated spaces like basements, attics, or crawl spaces needs to be insulated. The polymers in PEX piping can flex slightly with temperature changes where rigid CPVC, PVC, or copper can’t. However, PEX piping can still freeze and burst when temperatures drop below 20 degrees Fahrenheit.

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While PEX pipes can and will freeze in cold weather, it withstands cold temperatures better than copper, PVC, or CPVC which is rigid and will burst easily. Manufacturers of PEX piping won’t provide a guarantee against the pipes bursting in freezing temperature.

As a general rule of thumb, if your PEX piping is traveling through interior walls or insulated exterior walls, you don’t need to insulate the PEX piping. However, any PEX piping exposed outside or inside an uninsulated area such as a basement, crawl space, or attic should be insulated, particularly if you live in an area where freezing temperatures are common.

While PEX is certainly growing in popularity due to its unique and adaptable features, the material is not invincible. There has been plenty of confusion regarding the standards and requirements for ensuring optimum efficiency, longevity, and safety.

Stick around to determine the fundamentals of insulating PEX piping compared to other piping materials and how you should approach the insulation process following manufacturers’ and professionals’ recommendations and guidelines. 

Should PEX Piping Be Insulated 

Yes, insulation is an essential part of installing PEX piping, as the lack thereof could lead to unfortunate outcomes. PEX piping is more resilient against fluctuations in temperatures than other commonly used materials. It is flexible and does not act as a conductor for heat and cold as easily as metal materials do.

Although working with such a material poses various advantages due to its flexible nature, PEX piping is still vulnerable to cracking when it’s not shielded effectively from freezing temperatures falling below 20 degrees Fahrenheit, as well as to various ultraviolet light sources which can cause destructive and corrosive damage over time. 

Ensuring that the PEX piping has protection from these threats prolongs the PEX piping’s longevity while still benefitting from its ability to contract and expand with cold, heat, and even water flow and pressure.

Insulating PEX piping also decreases the risk of potential functional failures due to moisture condensation and promoting energy efficiency. Limiting the exposure risks and insulating PEX piping reduces water pipes’ chances of bursting or leaking and causing tiresome and frustrating outcomes, which may be costly to repair, not to mention the potential necessity for piping replacement. 

PEX Pipe Insulation Requirements

Another important factor to consider is that the standards and requirements are applicable across all piping types, whether copper, CPVC, PVC, or PEX piping.

  1. ASTM Standard Requirements and Sizing for PEX Piping

PEX piping is generally available in standard sizes ranging from ¼ to 2 inches, at a length of 50 to 200 feet. It’s crucial to calculate the pipe’s size with the amount of insulation that will be necessary. According to the American Society for Testing & Materials, the standard for PEX piping is CTS, which is also the standard for copper piping and CPVC. 

PEX piping can be insulated with the same foam insulation sized for copper, commonly found in home improvement stores. The standard IPS sizing can be applied to PEX piping and effective for insulation, but the fit would not be as snug due to inaccurate size.

That being said, trapped air space commonly plays a role in various insulation techniques. Such an approach would be efficient enough and may even add additional insulation based on this principle. So, it’s important to select piping insulation that is properly sized for a proper fit.

  1. Type of Material for Insulation of PEX Piping

Foam is usually the recommended type of insulation for PEX piping, as it meets the flexibility levels that such material demands. Since PEX is commonly used with curved positioning instead of connection joints, the insulation material needs to be flexible. Fiberglass insulation is far more rigid and would not be able to accommodate such tractability. 

  1. Type of Fit for Insulation of PEX Piping

Once the correct insulation material has been identified, the appropriate type of insulation will need to be chosen. Persons can select between a continuous length and polytype, both of which have various features and benefits for users. While the continuous length type can be useful for PEX pipe, which spans over a long area, polytypes are generally better suited to PEX flexibility and are easier to apply post-construction. 

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Continuous Length Type: This type of insulation can be described as a full-length tube with no openings of necessitated closures, which offers thorough and even insulation across the entire length of the PEX pipe. While this would certainly be beneficial, this is more commonly used during the building’s construction phase, as it can be slipped over the PEX piping before it has been installed within the building.

Utilizing a continuous length type of insulation will not be practical post-construction unless the PEX pipe is removed and disconnected completely or if the insulation is cut, which may defeat the purpose of selecting the continuous type. 

Poly Type: This type of insulation is far more practical and simpler to apply since it is flexible and can be used in awkward spaces or angles, common with PEX piping, which is used in corners with bent positioning as opposed to the use of elbows for corners. 

For installing insulation post-construction, insulation with an opening on one side is the most practical, particularly for odd spaces, tight corners, and event tees. It’s crucial to ensure that the PEX piping is thoroughly cleaned with a wet cloth before installing and insulating, as it is commonly laden with dirt, grime, or debris which may build up over time, promote corrosion, and may not accommodate adhesive as well as a smooth and clean surface would. 

The PEX piping should be covered by the insulation and fitted snuggly by pushing down the insulation until the pipe pops into place. After the insulation has been fitted, the opening would be sealed off by pulling off the protective strip to reveal the adhesive. The seams would then be pushed together to seal the insulation completely. Many professionals also make use of contact cement for joining the ends of insulation lengths for further durability.

How to Insulate PEX Piping

Plan Where PEX Pipes Are Run

Insulating a new home involves proper planning. It’s a good idea to route PEX pipes through interior walls rather than exterior walls where possible. The heat from your home’s heating system can prevent PEX pipes from freezing.

When outside temperatures are 2o degrees or lower, keep your interior temperature at 55 degrees or higher. This will keep your interior pipes from freezing.

Insulate PEX Piping Exposed Outside

Sometimes, having PEX pipes outside can’t be avoided. Pipes must be run for exterior spigots (hose bibs) or other uses such as tankless water heaters. Any PEX piping exposed outside needs a minimum of R3 (3/8″ thick) piping insulation. Some colder climates require an R4 (5/8″ thick) or higher pipe insulation.

Insulate all exposed PEX pipe and secure the pipe inspection in place with tape along seams and bends where pipe insulation is loose.

Open an Interior Faucet During Freezing Temperatures

When a hard freeze occurs, generally 25 degrees or lower, it’s a good idea to open the cold water tap on an interior faucet to allow the water to dribble out a small stream of water. Flowing water won’t freeze as easily or as quickly. This also reduces water pressure on the walls of the piping.

Winterize the PEX Pipes in Vacation Homes

If you have a secondary vacation home that you don’t visit in the winter, you should consider winterizing the plumbing. Winterizing the plumbing includes draining the entire plumbing system, including the water heater and toilets. The cold won’t hurt the plumbing system when water is not present. Also, insulate the plumbing P traps under sinks and inside crawl spaces or basements.

PEX Piping in Basements and Crawl Spaces

Crawl spaces and unfinished basements are particularly vulnerable spaces for PEX piping during the winter months. These spaces are not heated or insulated like the inside walls, which can cause the pipes to freeze if it gets cold enough.

Your hot and cold water supply lines (as well as your PVC drain traps) need to be insulated in unfinished spaces. Often, these pipes and freeze and crack along connection joints. PEX will expand about 1 inch to 2.5 inches per 100 feet for every 10-degree temperature change. This can help prevent some damages from occurring. However, in short spans of PEX pipe, freezing and cracking can and likely will still occur.

Insulating the hot side will assist in delivering hot water to fixtures quicker and the water inside the pipe cools at a slower rate. The cold water side may condensate in the summer months contributing to damp crawl space conditions.

PEX Piping in Attics

When installing insulation for PEX piping in an attic, the most challenging part is the tight spaces, sharp corners, hangers, joists, and tees running across the area. The use of PEX and foam insulation will provide enough flexibility to cope with such factors, coupled with open insulation on one side.

This allows users to have varying approaches for applying the insulation, such as trimming it and running it from the opposite end for tees, mitering the insulation at elbow curves, and securing the ends with cable ties for extra hold and support for the adhesive.

PEX piping in the attic is susceptible to fluctuations in climate and temperature as they are more exposed to outdoor conditions. Both the hot and cold lines should be insulated effectively, as insulation of the hot side will assist in delivering hot water to the load faster. In contrast, the cold line’s insulation will lower the risk of condensation forming in summer, which may cause seepage through the ceiling. 

Conclusion

Insulating PEX piping is a fundamental part of establishing a highly functional plumbing system with optimum efficiency. Taking the time to invest in this crucial process will be a fantastic investment in the long run. Having PEX pipes coupled with proper insulation will ensure that the piping is protected during freezing temperatures.

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Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started HomeInspectionInsider.com to help people better understand the home inspection process and answer questions about homeownership and home maintenance.

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