Screed thickness

If an excessively thick screed (greater than 90mm/3.5") has been used, or a 'thermally massive' covering such as flagstones has been laid above then the underfloor heating will take longer to respond.



A knock-on effect of this is that by the time the thermostat has sensed a comfortable air temperature there is a store of heat in the floor, which it continues to release. Because of this the room becomes hotter than desired. If this is happening then there are two options for overcoming the situation.



Firstly the mode of operation can be adjusted to allow for the large thermal mass. By adjusting the thermostat slightly lower than previously, or reducing the heating period overheating may be avoided.



Otherwise it may be prudent to fit an 'optimising' thermostat in place of the existing room thermostat. These tend to be programmable thermostats, and there may be complications if the existing system uses dial thermostats with a separate programmer.