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Under Floor Radiant Heat Install Diary
Heating University Main Page |
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HouseNeeds.Com is here with more how to. This time it's pex under floor radiant heat. One of the most popular retrofits and new construction pex radiant applications is placing PEX under the main living space of a home or business. |
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Skill Level: Moderate Tools Required: Right angle drill, hole saw, PEX un-coiler (can be homemade or use an extra set of hands) and staple gun Time: four hours plus, depending upon the size of the floor |
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click image for larger picture
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A pex radiant floor heating system can be the most comfortable, efficient and often may be installed for less than other heat delivery hydronic systems. Radiant floor heat stratifies the heat from the feet to the head. The feet are always warmer than the head; this is what feels naturally comfortable to our bodies. Objects that rest on the floor become charged as well, magnifying the effect. This allows us to run lower temperatures when compared to a forced air system or hydronic baseboard heaters. |
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Installing PEX Tubing Under Flooring; for hung PEX Tube or heat transfer plates This suggested method is for a traditional solid joist floor. We feature this information and more in the Heating University Section of Houseneeds. You should always check with your builder or architect for a suggested drilling location, for your floor. The process begins by drilling the necessary holes, positioning the manifold in a central location and attaching the first run to the manifold. A PEX un-coiler can make this process much easier. It is critical to uncoil the PEX in a linear fashion, to prevent kinking. |
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4 Loops of an under floor radiant application This floor layout shows 4 loops attached to one manifold. Here the manifold is placed in the center of the floor, making it easy to keep our loop lengths even. Typical loop lengths are set at 200’ to 300’ maximum, keeping the distance to the circulator as part of the maximum loop length. At HouseNeeds we can specify the tubing needed for a particular application. |
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There are several ways to attach the PEX to the sub floor. Here are two examples of heat transfer plates. The top is an extruded plate, very thick and positively holds the PEX in a crescent shaped track. The heat transfer plate on the bottom is a stamped plate, where the plate is positioned over the PEX and stapled up. Both plates quicken the response times for the floor and distribute the heat evenly across the floor. The extruded heat transfer plates will transfer heat a little better due to the mass of the extruded plates. Also, the PEX tubing will be held in place better and thus will be quieter. |
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Slide brackets are ideal for retrofits where nails protrude down or there is a concern about heat
transfer plate noise. Slide brackets cost less than heat transfer plates and allow higher water
temps. The PEX tubing is positioned under the floor on slide brackets, 8" on center with in 16" on center
joists. The brackets allow the PEX to be placed just below the floor, so it does not touch and then
zip ties hold things firmly in place. Other methods of attachment include PEX clips, talon clamps and ultra fin. Noise is always a consideration. Many installers either firmly mount transfer plates or use a clip with a stand off, to avoid noise. |
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PEX stand off clips for under floor radiant heat installations. The clips are screwed in one by one
and firmly clipped to the PEX. Click here for more installation info using PEX Stand Off Clips. |
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Ultra-Fin with Alum-PEX Water is circulated through the tubing in the under floor joist spaces of your home, where heat is then conducted to the attached aluminum fins. |
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RB Stand-off Clips, RB Fluch Mount Clips and Staple Guns |
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Protection sleeve should be used to prevent chafing of the oxygen barrier on the PEX. The sleeve is split and is positioned after the PEX is installed. Here we see the back run of the first loop and two joist bays with in one loop. |
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The PEX is in place and insulation is stapled below the tubing. We recommend Low-e Foil Insulation. |
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Radiant Floor Foil Insulation is highly recommended with under floor radiant. The insulation should be
placed at least 4 inches below. The goal is air stagnation, allowing heat to rise. Placing the foil
faced foam closes the space and send the heat up. Note: The homeowner has kept all wiring below, preventing the heating of the wires. |
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The PEX manifold feeding the floor is in the center span in this house. Placing the manifolds in a central location allow the loops to stay with in recommended lengths and reach all parts of the house. Typical loop lengths are set at 200’ to 250’, keeping the distance to the circulator as part of the maximum loop length. |
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The PEX manifold feeding the floor is in the center span in this house. Placing the manifolds in a central location allow the loops to stay with in recommended lengths and reach all parts of the house. Typical loop lengths are set at 200’ to 250’, keeping the distance to the circulator as part of the maximum loop length. |
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