How and why to install concrete floor radiant heating. Radiant floor heat in concrete slabs for your home or driveway heating.
There are two types of concrete floor radiant heating systems;
using a large thermal mass of a concrete slab floor while the other
lightweight slab over a wooden sub floor.
Concrete radiant heating is the great option as the main heating system; it is the cheapest system, it saves the energy, it provides healthier and comfortable living.
Temperature of the radiant floor heating in slabs is easy to control, and it is consistent; there are no drafts and blowing air.
In hydronic heating hot water circulates through the heating pipes so these are known as "wet installations".
Electric heating can also be used in radiant heating, and it is cost effective as long as it heats the thick concrete floor, with the affordable electricity rates of course. Thicker floor will store the heat longer and make your house comfortable for hours without any further electrical input.
Radiant heat in concrete slabs is retained so the open doors or large windows will not affect the temperature inside your home as much as with forced air heating systems. Concrete floor with the high density (high R-value) insulation placed below the slab makes the floor one big radiator.
The best time to install concrete floor heating is when installing a concrete slab. Why?
Installing a concrete floor radiant heating is not hard DIY project, but it needs some skills and knowledge. This is also known as the slab-on-grade installation.
Here is the video example: How to Install Radiant Floor Heat Tubing in a Slab On Grade
If you are already paying for the installation of the slab, recommendation is to install the floor heating also, since the only cost is adding very affordable PEX tubing, plus labor of course.
In this case, when installing concrete floor heating for the whole house, there will be no need to buy pipes or heaters that will occupy your valuable home space.
PEX tubing that is installed inside the concrete slab should be protected against the damage and freely transport hot water.
During the installation of concrete floor radiant heating reinforcement wire mesh should be positioned properly in the slab area and prior to pouring concrete. Polyethylene vapor barrier and the insulation are also needed for efficient heat distribution. PEX tubing is then attached either by the wire ties or special clips. The idea is to secure the tubing, and the best will be to follow the manufacturer instructions.
PEX tubing will be looped inside the concrete floor and the spacing between the loops will provide more or less heat. Recommendation is to keep the loops one foot apart to make the bending easier and provide the unobstructed hot water flow.
Depth inside the concrete slab at which you will lay the PEX tubing will also determine are you going to use hot water with higher or lower temperature and how long does it take to heat the floor. Recommended concrete slab thickness should be between 4 and 6 inches.
The location for the most efficient and safest installation is somewhere in the middle of the concrete slab and installation should be without any joints. Use the full length of the tubing whenever you can as there is always a possibility for leakage where the joints are.
With or without joints, new floor radiant heating system should be checked before concrete is poured, to see are there any defects in the system. This is done by using the air pressure of 50 psi, and the tubing must maintain the pressure for 24 h without leaking.
Covering that goes on the cement floor also has a great impact on the heat transfer. Tile floor, for example, has much better heat transfer than the carpet. Installing the insulation under the sub flooring can control the efficiency of the radiant heating. Recommendation is to buy and install the insulation with the R-value that is greater than the R-value of the floor covering, so heat can go up, not below.
Thin-slab concrete floor radiant heating is a better choice than the above solution. If you already have an existing concrete floor, radiant heating system is installed above the larger slab. On the wooden flooring, you can pour the thin slab of concrete over the PEX tubing, allowing retrofitting over existing concrete floor and without significantly raising the floor height.
PEX tubing is secured to the wood sub flooring, not to the reinforcing wire as in the example above. The height of the thin-slab of concrete is usually 1.5 inches or 38 mm so the tubing must be installed tightly to the floor to prevent protrusion the concrete.
Thick concrete slab system due to its high heat capacity is perfect for storing the heat from solar heating systems, which are having fluctuating heat output. The disadvantage of thick concrete floor radiant heating systems is their slow thermal response time.