PEX Radiant Floor
Hydronic Radiant Heating System

PEX radiant floor tubing

A PEX radiant floor involves laying down a tubing circuit into a floor. The PEX tubing will then have hot water run through it which turns the entire floor into a radiant heat source. PEX stands for cross-linked polyethylene, which is made synthetic rubber or polymer tubing. You do have to make sure the PEX tubing you choose has an oxygen-diffusion barrier. If oxygen flows freely in a radiant system, it can damage iron or steel components in a boiler or circulator.

A radiant heat system consists of a series of tubes or electrical wiring laid underneath the floor. The tubes or wiring carry heat or energy in specific zones and emit or radiate heat to the surface.

When radiant heating was introduced, it was intended to be hydronic that is, they employ warm or hot water to heat surfaces. In the beginning the tubing used was copper mainly for its heat conducting properties.

Copper had the disadvantage of rendering a system inoperable if a piece should break off, and replacing copper pipes is quite costly.

In older radiant heat systems, copper was installed into concrete slabs. Copper is no longer used for two reasons. First, copper is much more expensive. Second, concrete and copper expand and contract at different rates, so in some systems the copper or concrete would crack. When PEX was introduced as the alternative to copper tubing radiant energy and heat became more viable and affordable. It thrives even in tough conditions and is built to last up to 200 years even embedded into concrete.

PEX is excellent for hot water applications. PEX is a form of cross linked polyethylene which is a very durable material a medium to high-density modified polyethylene with improved properties. The chemical composition of PEX and the bonding structure means that unlike most plastics, it resists creep deformation even under very high temperatures.

PEX Radiant Floor Tips

You can follow the tips below to protect your tubing during storage, its unrolling and during the actual installation:

First of all PEX tubing is only meant for indoor applications and should be stored away from direct sunlight, like most polymers PEX is susceptible to damage by UV rays emitted by the sun. It is best to keep PEX covered while it is under storage awaiting use and installation. Do not put PEX next to a window and never leave it outside without adequate cover. Do not buy therefore PEX that has been stored in some outdoor yard regardless of how long the supplier tells you it has been outside for. UV lighting accelerates the aging of your radiant heat tubing.

Protect you PEX tubing from dirt. You can keep debris out by tapping the ends up which should stop everything else from dust to pet hair that shouldn’t be in PEX tubing.

When uncoiling the PEX tubing, roll it off the roll and look out for markings. Some manufacturers mark areas with kinks and holes such areas are better spliced, so take note of those markings.

There are various ways to install your tubing. You could staple it up but when you do make sure that the radiant heat tubing is taut and doesn’t sag. Support your tubing at 16 inch intervals and insulate portions of tubing that have to run close to lights. Do not install near to a toilet as the heat could potential melt the wax. Nor should you install radiant heat tubing under your refrigerator or stove or kitchen cabinets. If you have to install tubing in those areas insulate the tubing with foam and put a piece of radiant barrier between sub-floor and the tubing under those appliances.

Last, when installing your radiant heat tubing, never let it rub on any electrical wires. This could damage the tubing and create problems in the future. If you ever have to call on an electrician make sure he known to work around you radiant heat system and be careful not to pull at wires. A little care will ensure that you have a trouble free system.

PEX Radiant Floor in Concrete or a Subfloor

For concrete floors, a PEX heating circuit is layed down on a wire grid. When the circuit is complete, the concrete can be poured. When the concrete is set, the PEX tubing will have warm water flowing through the circuit. The thermal mass of the concrete will be able to radiate heat for hours.

There are a few different types of PEX tubing. A common choice for concrete applications is Wirsbo PEX tubing with oxygen-diffusion barrier.

Other systems work better with specific types of PEX radiant tubing. For instance, Warmboard uses PEX Aluminum PEX. This type of PEX actually has aluminum in the core. Warmboard is a unique radiant system because Warmboard is the subfloor. The PEX tubing rests in a pre-cut channel which allows the radiant heat to be very close to the finish flooring.

Warmboard with PEX-Aluminum-PEX tubing.

In some cases, PEX radiant floors are installed directly below the subfloor. Aluminum flashing is attached below the subfloor, and a PEX tubing circuit will run through it. Then insulation has to cover up the PEX to make sure the radiant heat goes up into the floor.

Below is a video of a PEX radiant floor tubing system being installed to heat a basement.

To learn more or to purchase PEX supplies, click here for Radiant Heat Tubing.

Related Articles

- Radiant Heat Tubing, Cross-Linked Polyethylene
- Radiant Heating
- Radiant Water Heat
- Concrete Floor Radiant Heating
- Warmboard Subflooring for Hydronic Radiant Heat
- Radiant Heat Boiler

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