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Will PEX Freeze in Crawl Space? (Is It the Best Option?)

Will PEX Freeze in Crawl Space? (Is It the Best Option?)

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Nowadays, PEX pipes have become the more popular plumbing option for both external and internal applications. Aside from their flexibility, they maintain their properties at a much wider temperature range than traditional copper or PVC piping. But will PEX freeze in crawl spaces?

Actually, PEX pipes are pretty freeze-resistant. They don’t burst as readily as other types of pipes do even after multiple freeze/thaw cycles. That said, you should protect your pipes with proper insulation if they’re running through a crawl space where the temperature regularly drops below 20°F (-6°C).

So let’s go over PEX properties and whether it’s the right option for your crawl space plumbing.

What’s PEX? And Is It Better Than Other Pipe Materials?

PEX, or cross-linked polyethylene, is a type of polyethylene polymer that gets reinforced through the process of cross-linking. This process simply means that the polymer units are connected to one another by several bonds at once, making the polymer both sturdier and more flexible.

Cross-linking is also why PEX pipes are more freeze-resistant. According to the Plastic Pipe Institute (PPI), PEX pipes can withstand temperatures as low as -40°F (-40°C) without losing their bendability. They only start to become brittle at temperatures lower than -180°F (-118°C).

In that sense, PEX pipes are better than copper pipes, that freeze at around 32°F (0°C), and can burst if the temperature drops to 20°F (-6.6°C). The same goes for PVC pipes, which lack the flexibility of PEX.

Can You Use PEX in a Crawl Space?

You can use PEX pipes in a crawl space. In fact, it’s a better option than other types of traditional piping in exposed areas such as crawl spaces, attics, as well as outdoor applications.

This choice should save you some money from the get-go since PEX pipes are pretty flexible and require fewer connectors when run around corners or in curved positions.

The fittings or connectors are the weakest points in any plumbing plan. These tend to burst at a higher rate than pipes, so minimizing their number protects your house from leaks should the temperature drop too low.

Do I Need to Insulate PEX in a Crawl Space?

Now that we’ve established that PEX pipes are a good choice for crawl spaces, we need to address the issue of insulation.

Most plumbing codes, including the ICC International Plumbing Code, agree on one thing; you should never install pipes in an outdoor space subjected to freezing temperatures “unless adequate provision is made to protect such pipes from freezing by insulation or heat or both.”

This means that you should definitely insulate PEX pipes in your crawl space if you live in an area where temperatures drop in the winter.

The IAPMO Uniform Solar, Hydronics and Geothermal Code (USHGC) even requires that any kind of pipe in a solar thermal system be insulated if the ambient temperature drops below 46°F (8°C). This should protect the pipes from expanding and contracting too much, causing premature failures.

Types of Insulation for PEX Pipes

There are a couple of options you have when it comes to insulation material for PEX pipes. You can either opt for foam or fiberglass pipe insulation.

Foam Pipe Insulation

This is a more modern material used for insulation. Foam works by trapping air inside the cell structure, and since air is a bad heat conductor, it stops heat from leaving the pipe to the ambient air.

Foam pipe insulation comes in two types, either a continuous length pipe that has no opening, or one with a seam along the middle and a self-adhesive. The first type is made to be installed with the pipe during construction, and the second can be done after construction.


  • More elastic and can work for corners
  • Higher R-value than fiberglass when using the same diameter.
  • Easier to install if you’re using prefabricated foam tubes


  • Heat sensitive, where it can shrink to the pipe surface if excessively heated.
  • Runs a little pricier than fiberglass.

Fiberglass Pipe Insulation

Fiberglass has been around as an insulation option for some time, and it excels as backing when you’re insulating interior walls.

You can also get fiberglass pipe insulation tubes that are pretty easy to install. You just slide them onto the pipe and seal them with the adhesive tape that comes pre-attached to the fiberglass tube.


  • Cheaper than foam insulation
  • Can be installed by amateurs


  • Needed in larger diameters which can make it impossible to install in some areas.
  • You should use a respirator or gas mask when working with it.

How to Insulate PEX Pipes in a Crawl Space

After you’ve decided which type of insulation to use, you can start the insulation process pretty easily by following these steps:

  1. Measure the length and diameter of the pipes running along the crawl space.
  2. Get the correct diameter of prefabricated insulation tubes and cut them according to the length of the pipes without the joints.
  3. Remove the self-adhesive tape backing and secure the insulation tubes to the pipes
  4. Cut pieces for the corners and use strong duct tape to overlap them with the pipe-length insulation
  5. Make sure there are no air gaps trapped inside, and that the whole length of the pipes is adequately covered with insulation.

This is a crucial step because when water freezes at two points along the length of the pipe, the ice plugs cause a piston effect that can lead to pressure buildup between them. This is actually the leading cause for burst PEX pipes, not the expansion of the pipes.

Final Thoughts

Will PEX freeze in a crawl space?

Well, PEX pipes can withstand freezing temperatures pretty well. They remain flexible even at -40°F (-40°C), but you generally want to avoid exposing them to too many freeze/thaw cycles.

That’s why you should insulate any PEX pipes running under a crawl space to avoid any burst pipe situations. This is especially important if you live in a place where the temperature drops below 20°F (-6.6°C) often during the winter.


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