Fitting radiant slab heat systems is best left to professionals, but if you would like to perform your own home improvements by installing a radiant heat system, then there are a number of mistakes that are easy to avoid, but which can be made by even professional installation plumbers. Making mistakes in installing radiant slab heat systems in concrete floors is difficult to correct, and once you have gone wrong in your installation, it can be difficult to set it right without digging up the entire system and starting from scratch. However, with due care and attention, even the beginner can avoid making some of these mistakes, and thereby ensure that their radiant heat system works well.
Installing a radiant heat unit using a concrete slab requires a lot of insulation. Concrete conducts heat well, but if you are not properly insulated, it is easy for the heat to travel in the wrong direction, and warm the ceiling below rather than the floor above. You should use installation all the way around the floor, before fitting any of the tubing. Remember that concrete passes heat to anything that it touches, so be sure that it does not touch walls or supporting wood boards which will conduct the heat to other parts of the house.
You should also protect the concrete slab and surrounding area from touching wood at the base of walls, or floor joists. Insulation in this area can in fact be an invitation to insects such as carpenter ants and termites, which will then invade the walls and floors, and are extremely difficult to remove. Take care that the insulation is also not made of grasses, or other vegetable matter that could have spores or fungi already in the material. Make sure that you buy your insulation material new, so that there is no risk of infestation from one house being transferred to your under floor heating system.
Your radiant heat slab should also include details such as the careful placing of radiant heat tubing within the slab. There are industry guidelines for how wide apart the cables should be set in order to provide the right sort of heating for your home, which ranges from 8 inches for carpet, to 2 inches for ceramic and stone tiling. Make sure that you know how far apart your cables should be before you buy the lengths. Also, don't place the tubing too deeply into the slab, anything more than 2 inches below the surface will make the floor cooler than it should be.
Take care not to have too large a pump for your radiant slab heat flooring. Radiant heat cables can only force water through the system at a certain degree of pressure, and increasing this will not put more air into the system, but will more likely result in the boiler and valve shutting down. If the boiler produces more than 20 degrees of heat between input and output, it is working at capacity, and you should not try and make it any hotter.