Hydronic Radiant Floor Heating Design and Installation

There are many different installation methods for hydronic radiant floor heating. The job is easiest when it is done with new construction. The system of interlocking tubes can be laid in the flooring and tied into the boiler system before the concrete slab is even poured. For retrofit jobs, the process becomes a bit more complicated because you have a preexisting home and floor to deal with. It can be done, though, and some methods are certainly easier and more cost effective than others. In this article you will learn about one particular method for installing hydronic radiant floor heating. It requires no pouring of concrete and no weaving of tubes through the sub-floor. Before that, however, it helps to know what hydronic radiant floor heating is. 

Hydronic Radiant Floor Heating

Hydronic indicates that the heat is channeled through hot water. Radiant means that rather than force hot air into a room, heat radiates into a space. In some systems it radiates from individual radiators in each room. In others, the heat comes through the floor as the hot water is pushed through. Thus, hydronic radiant floor heating is a system of central heating that circulates heated water through tubes running through the floor, transferring that heat into a room. 

System Design

One of the biggest considerations to make when you want to install such a system in your home is how to go about doing it. In homes without basements, the concrete slab is already poured. It would be extremely cost ineffective to remove all of the furniture and flooring, break up the slab and install tubes only to refill the whole area with concrete. Homes with basements sometimes can run the radiant tubes through the floor joists or sandwich them between pieces of MDF or plywood. This requires a lot of modification as well. A more recent method for retrofitting hydronic radiant floor heating is much less labor intensive. Homeowners can pre-order the control manifold for the boiler and the radiant heat controls which are built according to specifications. Once those pieces and the boiler or water heater are in place, it is a matter of laying the tubing in the floors of the home. 


To install this type of hydronic radiant floor system, all of the home’s carpeting, linoleum or other materials and sub-flooring need to come up. You will be installing the tubing on top of the layer of material directly above the floor joists or slab. The way it works is as follows: 5/8 inch sections of MDF are covered on one side with a thin aluminum coating. They fit modularly in a room. The pieces all have grooves cut out in them. They fit together in a grid and once in place, there is one continuous groove zig-zagging back and forth through the room. The groove starts wherever the water comes in, snakes around the room and exits just 1 or 2 feet from the supply in. 

Into the grooves fit 3/8 inch red PEX tubing. It is flexible, has the ideal inner dimension for hydronic floor heat and transfers the heat efficiently. The aluminum coating on the MDF further increases the efficiency of the system. The heat is reflected upwards through the flooring. Once in place, the flooring goes on top of the tubing and MDF. Different types of flooring have different heat efficiency ratings. Granite and ceramic tile are among the best in storing and transferring heat. 

Each room to be heated is equipped with such a design and the entire system is connected to the control manifold. It is installed on 3 circuits to reduce heat loss. As water is heated in the boiler, the pumps circulate it around the home where it transmits the heat before returning to the boiler. With the system calibrated to the particular home, it is a very efficient means of central, letting homeowners realize a 30 to 40% savings over the long run.