Heat emitters

Underfloor Heating for Suspended Floors

Heat emissions are suitable for installation on suspended floors
Heat emission plates are used for installing underfloor heating on suspended floors

Underfloor heating systems can be installed on suspended floors but there are some important installation considerations that installers need to note. In this blog, we will explore the topic of suspended floors and how solutions, such as heat emissions plates, can make UFH a viable heat emitter choice for this type of floor construction.

Suspended floors have a void underneath the floor structure and usually timber joists are used to form the floor. Given the nature of their construction, whereby they are not solid, suspended floors can present installers with additional installation considerations when it comes to fitting underfloor heating on this type of flooring structure. In this blog, we take a closer look at the heat emission plates that Grant UK supplies which are designed for installation on timber suspended or battened floors.

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Is it possible to have underfloor heating with suspended floors?

Yes, certain types of underfloor heating can be installed on a suspended timber floor with wooden joists, whether this be on the ground floor or on upper levels. Grant UK’s heat emission plates are suitable for use with this type of flooring when there are joists or supports at 400mm centres. It is important to note that these heat emission plates are compatible with the Uflex 16mm PE-RT pipe only.

Heat emission plates - underfloor heating for suspended floors

The heat emission plates supplied for installation with the Uflex 16mm pipe are aluminium sheets which have grooves within them with fixed pipe centres of 200mm. To be installed, they must be adequately supported and, as we will explain in more detail later, the plates must be in contact with the both the insulation beneath the floor and the underside of the floorboards installed on top. Grant UK’s heat emission plates are supplied in packs of 28qty plates which have a floor coverage of 15.3m².

To learn more about Grant heat emission plates, please download the Uflex UFH Installation Guide or speak to a member of our Design Team.

The benefits of underfloor heating with suspended floors

Underfloor heating systems have many benefits when installed on solid floor constructions and some of these benefits can also be enjoyed when installed with suspended floors. Firstly, homeowners can maximise the space in their home because their heat emitter will be installed beneath their feet with no need to use wall space for conventional radiators. Secondly, underfloor heating systems evenly distribute heat into a room, keeping all the occupied areas of a living space comfortable and with no cold spots or draughts. Thirdly, an underfloor heating system can improve the energy efficiency of the heat source and, in particular, UFH is an excellent heat emitter to complement the efficient operation of a low temperature heating system, such as a heat pump.

Installing underfloor heating with suspended floors

When installing an underfloor heating system using heat emission plates on a suspended floor, insulation is key. For the system to operate effectively, insulation (such as 100mm of mineral wool) should be installed between the joists so that it is in contact with the underside of the plates. Any air gaps between the insulation and plates should be avoided because they will reduce the performance and effectiveness of the UFH system. To ensure that the insulation remains in contact with the underside of the heat emission plates, the insulation must be well supported and this can be achieved by fitting boards (such as plywood) between the joists.

Requirements for underfloor heating

Before starting an installation, it is important that installers thoroughly plan the design and layout of the UFH system in advance. For example, heat emission plates normally cover approximately 80% of the floor area and it is important that the plates never touch or overlap each other. Their orientation must also be thoroughly planned so that the laying of the Uflex pipe can fulfil the design requirements of the room or area in which the system is installed. Grant UK’s heat emission plates can be installed either running parallel with the joists (whereby the plates rest directly on top of the face of the joists or on battens fitted to the top face of the joints) or they can be installed running at right angles to the joists (supported on ‘cross battens’ that are fixed to the top face of the joists).

Grant UK’s in-house Design & Specification Team can assist installers with the design and layout of a Grant UFH installation.

How to install underfloor heating with suspended floors

For comprehensive support about how to install heat emission plates with the Grant Uflex 16mm PE-RT pipe, installers and heating engineers should refer to the Grant Uflex UFH Installation Guide. However, we have provided a quick summary here of the key steps involved when installing underfloor heating on a suspended floor.

Step 1 – preparation

In addition to thoroughly designing the underfloor heating system in accordance with the heating demand of the room and its heat loss, installers also need ensure the floor insulation complies with Building Standards. If the cross battens are needed, these must be fitted prior to the plates being put into position. Careful consideration must also be given to the location of the plates around the manifold, along the feed pipe routes, where the pipes congregate together and any points where cross joists are at right angles.

Step 2 – installation

Once the necessary preparatory works have been completed, the heat emission plates can be laid. The heat emission plates should be laid out first before being fixed so that installers can leave sufficient gaps between the ends and sides of each of plate, and also leave sufficient space between the end of the plates and the wall. Only once the appropriate number of plates are evenly spread out across the entire area should they be fixed. If necessary, the heat emission plates can be trimmed by no more than 30mm and further information about how to cut the plates can be found in the Installation Manual.

When it comes to fixing the plates to the joist, this can be achieved by using staples. if battens are not being used it may be necessary to either notch or drill the joist to allow the pipe to cross each joist to the next plate. Before doing this, installers should check with the local building control or a structural engineer to ensure that the floor joists are suitable to be notched or drilled. Any holes that are drilled must be done on the centre line of the joist and must not exceed 0.24 times the depth of the joist up to a maximum of 65mm in diameter. The correct location and size of the holes in the joists must be taken into account when positioning the heat emission plates.

Once the heat emission plates are laid and fixed into position, the Uflex 16mm PE-RT pipe can then be laid. Ideally, flow pipes should be directed to the coolest parts of the room and the pipe should be accurately laid as per the line drawings designed for the project. Pipes should not cross over each other, congestion around the manifold should be avoided and appropriate pipe bend supports must be fitted as required. The pipe should be gently pressed by hand into the grooves within each heat emission plate and once all laid, the connections can be made to the manifold.

Installers should then inspect the system to ensure that the installation is correct and that the pipes are held firmly away from any possible risk of damage. After the pipes have been laid and connected to the manifold, the system can then be filled and pressure tested.

Step 3 – floor covering

A suitable floor covering should be fitted on top of the system as soon as the pressure testing has been successfully completed to protect the pipe and panels and to prevent damage from any foot traffic. This floor covering can either be an intermediate layer such as a lightweight flooring cardboard or polythene sheet, or it can be the final floor covering. If laminate flooring is laid, this should be a minimum of 7mm in thickness with interlocking joints and if chipboard or plywood is laid, this should be a minimum of 15mm thick with flued tongue and grooved edges.
step by step heat emission plates installation

Become a Grant underfloor heating installer

If you are interested in installing Grant’s underfloor heating systems, such as the heat emission plates for suspended floors, a number of training resources are available. A one-day Underfloor Heating Training Course is available at the Grant UK Training Academy which covers the basic principles of UFH, system design considerations and full details about all the Grant Uflex systems from their installation through to filling, pressure testing and commissioning. A free on-demand Underfloor Heating Overview online course is also available via the Grant eLearning Academy. For further information about any of these courses, please contact our Training Team.

Helen Rishworth
Content & Communications Manager at Grant UK
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