Radiant floor heating offers plenty of options for installation in concrete. You can embed systems into slabs before they are poured as would be the case with new construction and you can add them to existing slabs or plywood subfloors and then cover them with thinset mortar. Two types of radiant heat systems are available -- hydronic and electric. Hydronic systems use PEX plastic tubing to route heated water below the floor. The water may be heated with gas, propane, electricity, wood or solar. Electric systems rely on power supplied through thin sheets of matting.
Instructions
Before Pouring Slab
1. Ask the radiant heating components manufacturer to determine the type and amount of insulation needed under the slab. Without insulation material, the slab transfers warmth to the ground and ends up being a large heat sink. The manufacturer considers the size slab, R-values (measures of thermal resistance) and even the water table to determine insulation requirements.
2. Install the required insulation material.
3. Lay PEX tubing in a snaking "S" pattern across the top of the insulation, or tie PEX tubing to rebar reinforcement. You can staple PEX to the insulation using caution to avoid rupturing the tubing or tie it to the rebar with wire ties. PEX must have at least 2 inches of concrete above the tubing.
4. Contact a contractor to pour the concrete slab over the PEX tubing. Be sure to leave the two ends of the tubing exposed so that they can be connected to the radiant heating system when it is installed.
Existing Slab
5. Determine how much added slab height you can live with in the room or house. Added slab height may mean trimming door jambs, re-installing base molding and it could affect cabinetry. Electrical matting increases floor height by about 1/8 inch.
6. Cut sheets of radiant heat matting to cover the floor and lay them on the slab. Be sure to keep about 2 inches of distance between the matting and plumbing or other fixtures. Pull off the protective tape from self-adhesive strips and press the matting tight to the floor, leaving no air gaps.
7. Spread thinset across the matting using a trowel. Be sure not to cover up the electrical connectors which an electrician will need to attach to the power system. Spread the thinset evenly and smoothly so it completely covers the matting. An alternative is to pour a self-leveling gypsum-based material over the matting. This material helps level out floors that have dips or flawed spots.
Existing Plywood Subfloor
8. Nail down sheets of channeled plywood to the subfloor. The channeled plywood has a series of grooves milled in it to make the installation of PEX tubing much easier and to keep the tubing below the surface of the floor. Nail the plywood into floor joists.
9. Guide PEX tubing into the milled slots in a curving "S" pattern, working from one end of the room to the other.
10. Trowel thinset onto the channeled plywood, making certain to cover the PEX tubing completely. Allow thinset to cure completely before adding flooring.
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