Underfloor Heating

Introduction to Underfloor Heating

 
Underfloor Heating is commonly used in mainland Europe and is becoming increasingly popular in the UK. It has a number of advantages and disadvantages over a conventional wet radiator system.

With an under floor heating system, the floor itself becomes the heat emitter and the heating of the room is from the floor up, unlike radiators in a normal central heating system where the emitters are mounted on the wall and by convection the room is, effectively, heated from the ceiling down.

Advantages 

 
•    Even distribution of heat across the room 
•    Unobtrusive
•    No restriction on the placement of furniture
•    Quiet in use
•    Very little maintenance is required
•    Individual room temperature control
•    No risk of contact with hot surfaces
•    Fabric temperature of building maintained

Water based under floor heating is often claimed to be cheaper to run than central heating using radiators, part of the logic being that the water used is at a lower temperature (typically 50°C rather than 60°C plus).

It is claimed that the same level of comfort is achieved with the temperature in an under floor heated room about 2°C lower than in a room heated with conventional radiators. Wall mounted radiators act as convector's to heat the air, with under floor heating, the whole floor area acts as an emitter for radiated heat.

With no need for wall mounted radiators, there is less restriction on placing furniture in the room also less 'dust traps' so the rooms are easier to keep dust free.

In wet areas, (bath, shower rooms, kitchen etc) the floors will dry off quicker.

 
The heat source is located under the floor and the areas to be heated are separated into separate zones (normally one zone per room) and each zone is heated and controlled independently.

Disadvantages 

 
•    Long heat up period
•    Requires major disruption on existing buildings
•    Long cooling down period
•    Cannot respond rapidly to quick temperature changes
•    Choice of floor finishing requires careful consideration
•    Changes of floor finish may affect performance

One of the biggest drawbacks is the relatively slow response time of under floor heating, especially where the pipe is embedded in a solid floor.

A wooden floor can take 30 minutes to an hour to warm up while concrete can take several hours - however the cooling time is also similarly long. This may not be considered a drawback if the property is occupied continuously or if the under floor heating is just used as 'background' heating.

 
Under floor heating should not be fitted under floor mounted units, which is quite easy to arrange in a kitchen where the position of base units etc are fixed, however it is not realistic to restrict the under floor heating in other rooms where the position of cupboards etc are not fixed and may be changed. Under floor heating beneath cupboards can cause the inside to 'sweat' and the effect of the heat may be detrimental to individual pieces of furniture.

 Back to top

How does an Underfloor Heating System Work ?

Generally speaking, most underfloor heating systems are warm water (wet) systems although electric (dry) systems are available. For wet systems, pipes are buried in screed, or run underneath the floor surface.

Underfloor heating systems operate by transferring heat from a very large surface, which is only slightly hotter than the room. Radiator systems transfer heat from a very small surface, which is much hotter than the room.

 
Typically, the temperature of the water in the underfloor heating system pipe is 45° – 55°C (compare this to approximately 80oC flow and surface temperature of a radiator system) and this warms the floor to a temperature of 25° – 28°C, which is comfortable to walk on.

In order that the whole floor area receives heat, the layout of the pipework should be considered carefully as each application will differ.

 
At the design stage there are a number of points that need to be considered:

 
•     Insulating affects of floor finish e.g. Carpets & Underlays 
•     Protection of floor finish from cracking (due to drying out)
•     Accommodation of thermal gains e.g. conservatory
•     Location of manifolds
•     Zoning requirements
•     Boiler/pump position and size

Controls are available to accommodate many different designs and to maximise efficiency so contact us at BLUE FLAME HEATING SOLUTIONS to discuss your requirements.

Where can underfloor heating systems be used?

Underfloor heating systems can be fitted as complete systems in new or major refurbished properties, extensions to existing houses such as conservatories or single or multiple rooms in a house. 

 
It is possible to combine both underfloor systems with radiator systems. For example, the ground floor could be heated by an underfloor system whilst the first floor is heated using a wet radiator system or radiators can be fitted in the bathroom and lavatory in homes where the main system is underfloor heating.

 
Natural Gas, LPG or Oil boilers can be used as the source of heat for any underfloor heating system. Condensing boilers being particularly suited as the operation of underfloor heating systems allows them to operate in their most efficient manner. 

 Back to top

Different types of floor

 
In new builds with solid floors, the heating pipe is normally embedded in the floor screed. This is by far the best method to use but only practical in new build or total renovation projects.

Suspended wooden floors can also be heated by pipes/cables mounting between the joists. However, timber is a very good heat insulator so special attention needs to be paid to the installation. The options normally offered to improve the transfer of the heat through the timber are:
• Using aluminium plates under the floorboards to spread the heat - more expensive in materials than the other options.
• Using a mortar filler between pipe/cable and floorboards - very labour intensive during installation - also very heavy (can be 25kg per sq. metre of flooring) so the strength of the joists needs to be considered.
• Clipping the pipe/cable under the floorboards (normally less than 25mm (1 inch) from the underside) - fairly cheap and quick but not as effective as the other options.
The effect of the heat on timber flooring should also be considered, timber with a moisture content of less than 10% should be specified to reduce the risk of the flooring drying out then shrinking, twisting or warping.

The effect of the heating on other types of flooring (e.g. laminates, vinyls) should also be considered and the manufacturer/supplier consulted if in doubt. The method of installing the flooring may need to be adjusted, i.e. thick underlay should not be used with laminates as they will act as a heat insulator, likewise using a heavy carpet underlay and carpet will act as a heat insulator and reduce the heating effect.