In-slab heating
For one room or the whole house, this type of heating has to be installed when in the process of building or renovating. As the name suggests, it is built into the concrete slab, with heating cables tied to the cement’s top reinforcing mesh before the slab is poured. In-slab heating enables you to place almost any type of floor covering over the slab and provides economical warmth 24 hours per day, 7 days per week. The system is specifically designed for connection to OffPeak. During the periods of the day or night when cheaper electricity is available, heat is automatically stored in the floor. The heated concrete then dissipates background warmth evenly throughout the room.
Frequently asked questions on floor heating
Q: Can “any” floor coverings be used over floor heating?
A: With the exception of some “hand loomed” carpets or soft bituminous backed carpet tiles, problems are relatively unknown. Coverings commonly used include: carpets, tiles of all types, cork, vinyl, slate, brick and parquetry. Problems can occur with parquetry or cork if the floor has not been dried sufficiently – pre-drying is recommended when these coverings are to be laid. This involves running the heating system at a moderately low temperature for a few weeks.
Q: If the heating cable is damaged can it be repaired?
A: Damage detected during the concrete pour or damage occurring during the later stages of building work can be located and repaired using special testing equipment. Since the cable does not absorb moisture, repairing the cable is very straightforward and does not require a large access hole.
Q: Can a suspended slab be heated?
A: Yes it can, but the exposed underside of the slab must be insulated to minimise downward losses. Styrofoam or polystyrene insulation boards are often used.
Q: Is supplementary heating required?
A: If steady 24-hour a day warmth is required, the building is well insulated and the correct electricity tariff is used, then generally no supplementary heating is required.
Q: Will a room overheat on a sunny day following a cool night?
A: Only if the building is not well insulated, has large areas of glass facing north and is also controlled by means of “air thermostats”. The use of floor-sensing thermostats combined with adequate levels of thermal insulation helps to overcome an uncomfortable temperature overshoot.
Q: Could the heating cause structural damage such as cracking of the slab or tiles?
A: No, because floor heating does not cause the concrete to become too hot – in fact it will not become as hot as your concrete footpath will become on a sunny day. Cracking may occur if the heating is used to cure the concrete quickly. The heating must not be activated for at least two months after pouring the slab or one month after tiles are installed into a sand/cement topping. So it is best to install in the off-season.
Q: Can the heating cable become faulty or burn out?
A: In a properly designed installation, controlled by floor-sensing thermostats, the cable will not be allowed to run hot enough to cause damage. There is a greater possibility of damage occuring during the concrete pour, or at a later date if holes are drilled into the slab or changes are made to placement of cupboards or built-ins.
