A Guide to Underfloor Heating

May 2014

A Guide to Underfloor Heating


Introduction to Under floor Heating

The concept of underfloor heating (UFH) was introduced to the world over thousands of years ago by the Romans who kept their rooms heated with hot air circulated through hollow spaces in the floors. This system has come a long way since then, evolving into one of the most cost and energy efficient forms of space heating today.
Modern underfloor heating works by disseminating heat at an even temperature through the floor, using heating elements (hot water pipes or electric mats) embedded beneath the flooring. This system eliminates the need for bulky wall-mounted radiators, using the entire floor area as the medium for transmitting the heat.
The two popular types of underfloor heating are:

Hot water Underfloor Heating ( Hydronic/Wet System)

In this system, a series of plastic pipes are laid in the sub-floor and hot water from a heat source such as boilers or heat pumps is pumped through the pipes at a low pressure. This is then covered using a special screed that conducts, retains and transfers the water heat to the floor.

Electric Underfloor Heating( Dry System)

This system uses electric cable mats connected to the power supply grids. The electric mesh is spread across the floor base with appropriate insulation beneath.

Underfloor Heating System                 Pros                   Cons
Hydronic/Wet System
  • Easily installed in new floor constructions
  • Relatively maintenance-free as there is no danger of leaks with the pipes being joint-free
  • Uses minimal amount of electricity


  • Higher installation costs
  • Requires more floor space for installing thick pipes. This makes it difficult for installation in existing buildings.(However micro–pipe systems are now available for use in areas with limited floor space)
  • Installation requires assistance


Electric/Dry System
  • Easy to install
  • This can fit under any floor types
  • Thin electric cables and mats can be fitted in to existing rooms
  • They work independently from the central heating system
  • Ideal for small scale installation such as bathrooms
  • Energy wastage is less
  • Can be easily fitted in upper-floor rooms
  • The cost involved in running it is higher, making it more suitable to smaller areas

Design Considerations for Underfloor Heating

The efficiency of the UFH is largely dependant on the design of the system. As per the current Building Regulations, most buildings do not require a heat output of more than 70 W/ sq.m. However it can vary depending on:

  • Insulation level of the building: Buildings with poor insulation would require a higher heat output ranging between 70-100 W/ sq.mConservatories and rooms with high ceilings also require a higher heat output
  • Type of Floor Construction: The heat output and performance of the underfloor heating system is also influenced by the type of floor construction used.Screed floors/solid floors: For screed floors/solid floors, the heat transmission from the heating pipes/electric mesh to the floor surface depends on the conductivity of the screed laid above the heating elements.
    Suspended timber floors: For suspended timber floors, special consideration should be provided in the design to avoid hotspots, which can cause shrinkage of the floor boards.
    Floating floor constructions: Floating floors may require an additional layer of insulation to improve heat retention and prevent downward heat loss to the ground.

The ideal operating temperature underfloor heating is determined in such a way that the temperature is not so high as to cause discomfort, but high enough to meet the heat losses from the building.
According to BS EN 1264, the maximum floor temperature should not be more than 9° C above the general room temperature, ie the temperature should not exceed 29° C for a room with an internal design temperature of 20° C. With UFH, the heat profile of the room can be maintained at a comfortable level of 20-21° C in the lower part of the room and 19-20° C around the upper part of the room.
It is important to consult a heating consultant/engineer to assess the heat loss of the building and draw up a design that provides optimal performance depending on the specifications. To know more, please call our expert team on 0845 500 4055.