Radiant Floor Heating Installation Options using PEX Tubing
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PEX Radiant Concrete Floors (Slab on Grade)
For concrete floors (slab on grade), the Radiant PEX tubing is attached to the reinforcing
mesh with cable ties before the slab is poured. This type of PEX Radiant Floor Heat has a
large mass.
With this type of radiant underfloor heat the space can only changed by the
radiant floor about 1/2 a degree per hour. Typically the water temperature used in pex
water line for this type of radiant floor is between 90° and 115°
Fahrenheit. It is imperative that the surface temperature of any PEX Radiant
floor stays below 85° or it becomes uncomfortable and unsafe.
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Radiant Concrete Floors (Slab on Grade)
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PEX in thin slab over wood framing
Simpler in new construction but you can install this type of radiant floor as a retrofit,
the radiant PEX Pipe is installed over framed floors and covered with concrete or lightweight
concrete. We like this type of pex radiant floor heating the best. Very easy to install and it
provides a very even heat. Thin slab PEX radiant floors have a much quicker response time.
With this type of radiant floor the space it is heating can be changed by the radiant
floor as fast as 2 a degree per hour.
Thin slab radiant floors have many floor covering options. (tile, stained concrete, wood using
sleepers, carpet, etc.). Typically the water temperature used in this type of radiant floor
- the pex water lines are between 90° and 125° Fahrenheit.
A quick note: When installing this type of
pex radiant floor heat you need to have a tension break between the concrete and the wood substrate
to allow the concrete and the wood floor to expand and shrink at there own rates. We recommend
using 6 mil. sheet plastic.
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PEX in thin slab over wood framing
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PEX Under Floor Systems with Heat Transfer Plates
In a typical remodeling project, the PEX radiant tubing is snapped
into radiant heat transfer plates which radiate heat to the floor above.
The radiant heat plates tend to make the floor above them have warm and warmer
spots. Still very comfortable. The installation of PEX under floors has its draw
backs. PEX when heated expands 1.1 inch per. 10 feet with a 100° temperature rise.
Typically the temperature for this type of installation is between 120° and
145° Fahrenheit. If not properly installed this PEX radiant floor can be quite noisy
or if you get the wrong type of transfer plates for your pex underfloor heating system.
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Under floor installation using
Radiant Heat Transfer Plates
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PEX Radiant Tubing Under Floor
In a typical remodeling project, the PEX radiant tubing is hung with hangers below the floor
about 1 inch. This allows the PEX radiant tubing to slide a little and sag a little as it expands making for a quiet floor. The hot water running
through the PEX radiant tubing heats the air which intern heats the floor above.
A insulation with a reflective surface mounted facing up leaving a 3 to 4 inch air space to
the bottom of the floor is required. The PEX Radiant Heat from this floor system
is very even. The air in this space must be stagnant, meaning all penetrations must be calked and
the floor joists where they meet the band joist also. Typically the temperature for this type of
PEX installation is between 120 deg. and 165 deg. Fahrenheit.
We know of many houses using this method, new construction and existing.
In Vermont where tubing was hung 16 inches on center and the water temperature is run from 125 degrees to 180
degrees out of the boiler or with a mixing valve. This has kept houses at a comfortable range with efficiency
and no noise. In warmer climates you can run with a cooler temperature, but all this depends on your house's heat
loss and other factors.
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PEX Radiant Tubing hung under floor
using air space and reflective insulation.
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