Underfloor Heating Explained

Underfloor Heating Explained

1- TYPES OF UNDER FLOOR HEATING

The two most popular forms of under floor heating systems are:

A. Electrical matting systems

B. Hot water pipe systems.

These are actually the most popular UK systems because they are easier to fit. Hardwood engineered floating floor sits directly above the matting, which is wired via a thermostat. Even heat distribution is essential as these systems are less prone to ‘hot spots’ that could potentially cause problems with your engineered floor such as de-lamination.

B. Hot water pipe system

This is very similar to your central heating system. A screed is generally used to house the pipes. Before fitting the floor, all screeds must be checked so that the relative humidity of the concrete has reached 75% or below. The most accurate way to test this is by drilling into the screed and inserting plastic plugs. After 24 hours you can return to then take readings.

**Installation can only begin once the level of relative humidity has been reached, and the under floor heating system has been fully tested and has been working for 2 weeks.

There are many brands for UFH available, make sure that you follow their instructions and advise as each system may have slightly different terms and conditions.

2- FITTING YOUR ENGINEERED FLOORING FOR UNDERFLOOR HEATING

This should be left to qualified installers recommended by the manufacturer of the UFH system and you must have “flow” control valves to ensure that the temperature never exceeds 27 degrees where the wood floor meets the screed or underlay. You cannot achieve this with thermostats.

Prior to installation, the installer/owner has the final inspection responsibility as to grade, manufacture and factory finish. The installer must use reasonable selectivity and hold out or cut off pieces with deficiencies, whatever the cause.

Use of stain, filler or putty stick for touch-up during installation should be accepted as normal procedure.

You must test the relative humidity of the environment the floor is to be laid in and also the moisture content of any sub floor or screed must be less than 4%.

3- MAINTENANCE AND USE OF THE FLOOR AND UFH SYSTEM

  • Many types of wood flooring are suitable for use with under floor heating (and cooling) – but not all. If in doubt, the first step is to consult a Specialist Supplier, the Timber Research and Development Association (TRADA), British Standard 8201:1987, or all three, as to the characteristics of the type in question.
  • Generally the temperatures should not vary drastically
  • The UFH should never be turned off, just kept at a very low temperature.
  • Always try to avoid taking the floor from one extreme of heat and humidity to another within a very short time-scale.
  • Ideally the room temperature should be 20 degrees Celsius and not lower than 18 degrees Celsius.
  • The air relative humidity should be between 35% & 60%.
  • If you turn it back on to full heat, this will “shock” the wood flooring and could cause lifting or the top layer of engineered boards de-laminating.
  • The maximum temperature of the wooden floor should never exceed 27 degrees Celsius to avoid excessive drying-out problems, which can cause stresses in the wooden floor.
  • A word of caution – the addition of carpets on wooden floors can add considerable heat to the temperature between floor and carpet. Thus to achieve a 27 C floor surface temperature (75 W/m2 output) may require water pipes to operate at a lower temperature.

4- HOW TO AVOID POTENTIAL PROBLEMS WITH WOODEN FLOORS AND UFH

Most of the problems associated with wooden floors and UFH come from the following conditions:

  • The lack of correct heat distribution, dramatic changes in the surface temperature: HOT SPOTS.
  • A high humidity in the room operating the heating above a surface temperature of 27 degrees.
  • Cleaning the floor with water and not a damp mop with the correct cleaning products.

If any of the above applies you can get the following wooden flooring reactions:

  • Warped boards
  • Engineered flooring that will de-laminate- this is the top layer coming off
  • Gaps appearing if not fitted correctly and you may also find the whole floor lifting.