Pressure Drops in Radiant Floors

Radiant Floors

• Instead of using space or central heaters, some homes have radiant flooring. Pipes built into the slab heat the floor. This heat rises from the floor to evenly heat the room without drying out the air like a forced-air heater. Radiant floors are best installed in new construction because the pipes are encased in the subflooring. The finished floor on top of the pipes needs to be able to conduct the heat from the pipes into the room. Avoid insulating carpeting and opt for wood or ceramic floors for a radiant flooring system.

How Radiant Floors Work

• Radiant floors are similar to hot water heating systems that use radiators. A boiler heats water. This water flows through pipes in your home, but instead of going to a radiator, the pipes carry the hot water to the subfloors for the rooms in your home. The pressure of the water ensures that it reaches the end of the pipeline and heats the entire floor.

Pressure Drop Causes

• Pressure drops in radiant flooring systems happen for several reasons. A hole in the pipe that allows water to leak out can remain unchecked if the soft copper tubing used for the system is not tested before the flooring is put down on top of it. Using pipe that is too narrow can result in a pressure drop at the end of the line because the pressure in a smaller pipe starts out higher and drops faster than in a larger pipe that maintains a more stable pressure. A system with standard tubing of 1/2-inch in diameter can experience greater pressure drops than 5/8-inch tubing, but the larger tubing is harder to work with to create the bends needed for the pipe layout of the system.

Pipe Layout

• The pipe layout under the floor will determine the amount of pressure drop. Some installers use a serpentine layout with curved bends in the pipe. This makes the system work harder and less efficiently because the long pipe runs create greater pressure drops. A grid layout, though more expensive in terms of installation, operates more efficiently because it does not have pressure drops as drastic as those in a serpentine layout. Regardless of the layout, pipe runs should be no longer than 200 feet to avoid pressure drops, according to R. Dodge Woodson in "Radiant Floor Heating."