GB2428085A - Underfloor heating - Google Patents

Abstract

An underfloor heating system and method in which the underside 21 of a floorboard layer is faced with metal, and wherein elongate pipe clips 22 are used to retain a continuous heating pipe 23. The pipe clips 22 are attached to the floorboards (10 figure 3) by any conventional means such as screws, and their elongate nature ensures that there is good heat transference from the heating pipes 23 to the metal-faced under-surface 22, whereby the heat may be spread evenly and efficiently about the floor surface. A later embodiment relates to an underfloor heating system and a pipe clip comprising an open-sided retention section for retaining a length of heating pipe.

Description

UNDERFLOOR HEATING

This invention relates to underfloor heating and in particular to a method of installing such heating, to an underfloor heating system for use with such method, and to a special design of pipe clip for use with the system.

The invention is directed to the provision of underiloor heating for hollow floors, in particular suspended timber floors. In many existing and new buildings suspended timber floors constitute the floors above the ground floor. Less commonly, the ground floor also may be of this type.

In modern building practice, suspended timber floors are built with timber or steel joists which are spaced apart, typically at 400-600mm centres. On top of the joists are fixed floorboards which together constitute a load distribution layer. The floorboards are typically of chipboard of 18 to 22mm thickness.

To heat up such a floor construction two possible techniques are used: 1) A sealed gap is defined underneath the floorboards, and between the joists, by providing a layer of thermal insulation generally parallel with the floorboards and spaced below the under-surface thereof.

The thermal insulation is usually provided between the joists, but may also be provided as a continuous layer beneath the joists. Within the air gap so defined, pipes carrying a heating fluid, typically water, are situated and act to heat up the air gap and thus the floor above. The pipework is fixed between the joists and has no contact with the underside of the floorboards. The heat transfer from the pipes to the floorboards is thus quite poor, being based only on radiation and convention within the air gap.

2) An air gap is defined, as in (1) above, but heat diffusion plates are used to support and fix the pipes carrying the heating fluid. The heat diffusion plates are attached in such a way that they are in contact with the underside of the floorboards so that heat transfer from the pipes to the floorboards is primarily by conduction. In addition, the heat diffusion plates are shaped so as to spread the heat conducted from the pipes to the floorboards as evenly as possible. For this purpose the heat diffusion plates are fabricated from a material having high thermal conductivity, such as aluminium.

Because of the greater efficiency of heat transfer, the thermal outputs which can be achieved with the heat diffusion plate systems are usually higher, like-for-like, as compared to the heated air gap system.

Therefore, for the heating air gap system to achieve the same level of thermal output as the heat diffusion plate system would require a smaller pipe space, and/or higher pipe flow temperatures.

There is a choice of installation methods for underfloor heating, depending upon whether the installation is to be carried out from above or below. Note that, in the case of a suspended ground floor, installation from below may not be possible due to restricted space.

If installed from above, the installer has to first fix the insulation, which is positioned beneath the pipework to prevent downward heat loss.

As mentioned, this will generally be fixed between the joists so that plasterboard or the like can be directly attached to the bottom edge of the joists to form the basis for the ceiling of the room below. Then the pipe supports, or heat diffusion plates (depending on the system being used) are fixed between the joists, and the pipework itself installed. Finally, the floorboards are laid on top of the joists. If it is found necessary to cross joists with the pipe it is necessary to notch out the top edge of the joists to accommodate the pipe.

In Figure 1 there is shown a typical underfloor heating system of the type intended to be installed from above. The system shown is marketed by Uponor Limited under the name WIRSBO (registered trade mark) and is shown installed in an existing floor supported by parallel timber joists 1. The system is installed by installing a layer of insulation (not shown) in the lower part of the space between each pair of joists I. Saddles 2 are next fitted across the space between the joists, these being supported on battens 3 screwed or nailed to the joists. The saddles provide support for battens 4 which extend parallel to the joists. The battens 4 are positioned so as to provide support for heat diffusion plates 5 which also extend parallel to the joists. Each heat diffusion plate 5 comprises an elongate plate in which is formed a U-section channel to locate a heating pipe 6. On either side of the U-section channel the plate 5 is formed with wings 7 which act to physically support the plate on the battens 4 and also to spread the heat supplied by the pipe to the floorboards (not shown) which are placed on top of the plates.

A problem with installing from above is that the installers have to work over open joists, with the danger that they could fall through into the space beneath, and injure themselves. Under UK health and safety regulations, where a worker is liable to fall a distance of two metres or more, safety equipment must be installed below in order to reduce the danger of a fall. This equipment is time consuming and expensive to install and intrudes into the room beneath, thus restricting access to that room.

Accordingly commercial builders prefer to install from below.

If the heating system is installed from below, all installation steps are generally carried out when the floorboards are already laid on top of the joists. In practice most installed systems are of the simple air gap type described above, and thus do not incorporate the advantages of the heat diffusion plate system. Generally speaking installation proceeds by fixing the heating pipes by means of conventional fixing brackets to the sides of the joists, or to the underside of the floorboards. After this, a layer of insulation is fixed underneath the pipes to create the sealed air gap between the floorboard and the insulation layer.

One commercial underfloor heating system which utilises heat diffusion plates, and is intended for installation from below, is made by Wavin Plastics Ltd under the trade name OSMA. A drawing of this system is given in Figure 2.

There is shown a plurality of parallel timber joists I over which is laid a layer of floorboards 10 and an optional floor covering layer 11. The basis of the system is a modular polystyrene panel 12 whose top surface is machined to form a pipe channel. Heat diffuser plates 13 are then fitting into each pipe channel. During installation, the panel 12 is pushed upwards from below until it comes into contact with the underside of the floorboards 10 and is then supported in this position by means of brackets 14, timber battens 15 or a screw and washer 16. Since the heat diffuser plates 13 are in contact with the underside of the floorboards, the heat supplied by the pipes is evenly spread over the floorboards and the transfer of heat is principally by conduction.

Whilst installation from below largely overcomes the health and safety difficulties described above, it has its own disadvantages. Since the heat diffusion plates, or their equivalents, have to be maintained in close contact with the underside of the floorboards a degree of precision is necessary in the installation: if the diffusion plates wholly or partly lose contact with the under-surface of the floorboards, even by a small amount, the direct conductive thermal link will be broken, and the efficiency of thermal transfer rapidly deteriorates; any such gap will have a high thermal resistance which will decrease the thermal output of the system.

Furthermore, in a modular system such as the system described above with reference to Figure 2, the installation effort is relatively high because the installer has to joint the panels together. If this is not carried out correctly leakage could result. The system is also relatively inflexible in that different sizes of panel are required for different joist spacings.

The present invention is concerned with an underiloor heating system which is intended to be installed primarily from below, and which overcomes the disadvantages of the prior art systems.

According to a first aspect of the invention there is provided a method of installing underfloor heating in a suspended floor comprising a plurality of joists supporting a floorboard layer, said method comprising installing said floorboard layer on said joists, providing elongate pipe clips made of thermal material, and attaching said clips to the underside of said floorboard so that said clips are in contact with the underside of said floorboard and installing heating pipe to said clips to be supported thereby.

According to a second aspect of the invention there is provided an underfloor heating system for a suspended floor comprising a plurality of joists supporting a floorboard layer, said system comprising a plurality of elongate pipe clips made of thermal material, said pipe clips having means whereby they may be attached to the underside of said floorboard layer, and one or more heating pipes located and supported by said clips.

In order to enhance the transfer of heat to the floorboard layer, it is preferred to provide one side of said floorboards layer - the side facing downwards - with a layer of thermally conductive material positioned against and in contact with said one side. Thus, when the pipe clips are attached to the underside of the floorboard layer, they make thermal contact with said layer of thermally conductive material.

The layer of thermally conductive material preferably comprises a sheet of metal. A good choice is aluminium, since aluminium combines reasonably high thermal conductivity with reasonably low cost. The sheet may be applied separately from the floorboard itself, but preferably the floorboard itself is faced on its underside with aluminium sheet during its manufacturing process, and therefore comes to the site already provided with a thermally conductive layer.

The sheet of metal may extend continuously over the under- surface of the floorboards, as where the floorboards are faced with the metal, or the sheet may be provided only between the joists, thus enabling installation after the floorboards are in place; however, the discontinuous nature of the sheet means that the heat spreading effect of the metal layer is not as effective, with "cold" strips being left over the joist positions.

Choice of the thickness of the sheet of metal needs some care.

Clearly the greater the thickness, the better the thermal conduction and the better therefore that the heat will be spread across the floor. However, increased thickness means increased cost, and increases the difficulty of fitting the pipe clips. We have found that aluminium sheet in the form of foil in the range 0.1mm to 0.2mm thick gives good thermal conduction whilst at the same time being easily pierced by conventional tools to enable straightforward installation of the pipe clips by simple means such as screws, staples or the like.

A particularly suitable type of pipe clip for the present invention forms a third aspect of the present invention. According to the third aspect of the invention there is provided a pipe clip made of a length of semirigid material, said length being shaped in profile to define an attachment section by which the pipe clip may be attached to a surface and an open- sided pipe retention section for retaining a length of pipe therein, and wherein the open side of said pipe retention section is orientated so as to allow the insertion of pipe therein when the pipe clip is attached to a surface.

This design of pipe clip is particularly suited to the underfloor heating system described above because of its ability to efficiently transfer heat from the pipe to a surface over a long length of the pipe. The orientation of the opening of the pipe retention section enables the pipe clips to be installed first, with the pipe itself later.

Preferably, said retention section comprises an open channel into which a pipe can be pushed to secure same therein, and wherein the attachment section comprises a planar section which is attached against said surface to maximise heat transfer to said surface.

The pipe clips are made from a thermally conductive material, such as a metal. Steel or aluminium would be good choices for the same reasons as above and fabrication may be from sheets of the metal suitably bent to the shape required. Alternatively, in the case of aluminium, the clip may be formed as an extruded profile which is later cut to size, either to pre-set lengths to form part of a kit, or as a longer length for cutting by the installer on site.

The pipe clips are elongate so as to enable them to securely and continuously hold a significant length of pipe. For example, a typical length might be I m. This maximises the heat transfer from the pipe to the clip, and hence to the underside of the floorboard layer. Preferably the pipe clips are straight, to hold a straight length of pipe, but they may also be curved to suit particular pipe layouts. During installation, the pipe clips may be cut to reduce their length, or two or more clips may be butted together in series to provide an effective longer length.

The pipe clips may be designed to hold one or more pipe lengths, as required. A preferred form of single pipe clip has an open P-shaped profile (see later) which provides an opening into which the pipe can be inserted in such a way that the resilience of the clip grips the pipe to closely retain it, and at the same time provide a good thermally conductive connection between the pipe and the clip. The "leg" of the P provides, in the elongate clip, a good-sized planar surface which is secured in contact with the metal layer against the underside of the floorboards. Securing of the clip is preferably by means of screws, staples or the like and, for this purpose the surface forming the leg of the clip may be drilled with a plurality of suitably spaced screw holes. Provided that the metal layer is not too thick (see above) the clips can be readily secured by screwing up through the screw holes, thence through the metal layer and into the floorboards. If the metal layer is too thick for this, then pilot holes have to be drilled through the metal layer at the positions where the screws will penetrate.

These pilot holes may themselves be used to secure the pipe clips, using self-tapping screws into the metal, or they may be of a clearance size to enable the screws to pass through into the floorboards themselves.

The pipe clips may also be designed to carry two, or even more, pipe lengths and an example of a design for carrying two pipe lengths will be described below.

The heating pipe used may be made of any material suitable to carry the intended heating fluid, usually water. Conventional, relatively rigid, materials may be used, such as copper, using conventional plumbing joints to join lengths together. However, it is preferred to utilise continuous pipe which passes from pipe clip to pipe clip and from inter-joist space to inter-joist space in a continuous circuit, with as few joints as possible. This eases installation considerably, and reduces the possibility of leaks. Such continuous pipe would normally be in a relatively flexible material such as soft copper or plastics material. Less flexible pipework can be pre-formed into particular shapes to suit a particular set of circumstances; however, as io a system, this offers less operational flexibility than using flexible pipe.

In order that the invention may be better understood, an embodiment thereof will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a perspective view from above of a section of a suspended floor incorporating a known underfloor heating system, of a type installed from above; Figure 2 is a sectional elevation of a section of a suspended floor incorporating a known underfloor heating system, of a type installed from below; Figure 3 is a side elevation of a section of a suspended floor incorporating an underfloor heating system according to one embodiment of the invention; Figure 4 is a perspective view from below of the underfloor heating system of Figure 3; Figure 5 is an enlarged detail of Figure 4; Figure 6 is a sectional view of a single-pipe pipe clip for use in the heating system of the invention; Figure 7 is a top view of the pipe clip of Figure 6; Figure 8 is a perspective view of the pipe clip of Figure 6; Figures 9 and 10 are sectional views of two alternative embodiments of pipe clips for use in the heating system of the present invention; and Figure 11 is an underside view of a suspended floor showing a typical pipe installation sequence.

Referring to Figure 3, the underfloor heating system is shown fitted to a suspended floor comprising a plurality of parallel joists I (just two are shown, for illustration) and a floorboard layer 10. Typically, the floorboard layer is 18-22mm chipboard. In the example illustrated, each joist has a composite construction giving an I-section, but this has no significance. A sheet 20 of plasterboard is shown attached to the underside edges of the joists I to form the ceiling of the room below.

The under-surface 21 of the floorboard layer 10 is faced with aluminium foil typically in the range 0.1mm to 0.2mm in thickness. A pair of pipe clips 22 are attached to the underside of the floorboard layer in physical contact with the aluminium foil. Typically the spacing of the pipe clips is such as to provide a 200mm to 300mm inter-pipe spacing; however, the number, arrangement and spacing of these pipe clips may vary from that shown, depending upon the circumstances. Each pipe clip is of a generally open P-section, and is intended to carry a single length of heating pipe 23. The single pipe clip is shown in more detail in Figures 6, 7 and 8, from which it will be seen that the pipe clip is elongate, having a length typically of I m, and is basically formed in two sections: a U-section 24 which carries the pipe (not shown in Figure 6) and a planar section 25 which is formed with a plurality of spaced fixing holes (not shown) which are used to screw the pipe clip to the underside of the floorboard layer by means of conventional woodscrews or the like. The foil layer is thin enough to be readily punctured by tools such as a bradawl or drill to enable the screws to be secured in the floorboard layer 10.

Advantageously the clips 22 are formed of a material having some elasticity, sufficient to enable the pipe to be pushed into the open side of the U-section 24 such that it is gripped and retained within the clip. Metal is preferred for the clip for its superior thermal properties, aluminium and steel being typical.

Attachment of the clips 22 to the floorboard layer in the manner described above brings the planar section 25 of each clip into firm and reliable contact with the foil, thus creating a continuous thermal path of low resistance for heat supplied by the heating pipes. Due to the fact that the foil covers all, or substantially all of the under-surface of the floorboard layer, the heat is spread efficiently across the whole floorboard surface to provide even heating to the room above.

To reduce downwards heat loss, a layer of insulation 26 (Figure 3) is positioned beneath the pipe clips 22 to provide an air gap 27 between the insulation and the under-surface of the floorboarding layer 10.

Figure 4 shows the underfloor heating system of Figure 3 in perspective view, looking from the underside. Figure 4 clearly shows the continuous heating pipe passing from one inter-joist space to the next and, within each inter-joist space, executing a U-shaped loop extending parallel to the joists to fully cover the full floor surface. Within each inter-joist space the pipe is attached by the clips 22 arranged, in the example illustrated, as two pairs of clips, one pair fixing each arm of the Ushaped loop. As clearly shown in Figure 5, at the remote end of the Ushaped loop the pipe curves around from one pair of pipe clips to the other.

It will also be noted that, during installation, the pipe clips 22 are orientated such that their pipe openings face outwards towards the joists on the nearer set of clips in Figure 4, and inwards away from the joists on the further set of clips (see Figure 5). This is deliberate, and is in order that the force of the pipe bends as they enter the clips tend to press the pipe the U-section 24, rather than the other way round.

Installation of the heating system commences by installing the floorboard layer 10, using, for example, chipboard having one surface faced with aluminium foil. The floorboard panels are placed with the foil surface facing downwards and are fixed to the top edges of the joists in the usual manner. No further access is required to the room above, and -11 installation continues from beneath the floor. The next step is to attach the pipe clips 22 in whatever arrangement has been pre-decided will give the required distribution of heat over the floor. Next, the continuous heating pipe 23 is threaded through the joists 1, using pre-drilled holes through the joists I where necessary. Within each inter-joist space, the pipe is carefully pulled through to give sufficient length for the required U-shaped loop. A typical installation sequence to achieve full coverage over a floor surface comprising three inter-joist spaces is illustrated in Figure 11. The drawing is self-explanatory.

Next the pipe loops within each inter-joist space are moved into position and secured in the respective pipe clips 22 in the manner illustrated in Figure 4.

Finally the insulation layer 26 is installed to reduce downwards heat loss. The insulation layer can be omitted if downward heat loss is not of concern.

Alternative designs of pipe clip are illustrated in profile in Figures 9 and 10, which are self explanatory. The pipe clip shown in Figure 9 has two U sections 24 and is intended for holding up to two pipe lengths; that shown in Figure 10 has twin planar sections 25a, 25b to give still further improvements in heat flow from the heating pipe.

The underfloor heating system described above should give greater flexibility over many prior art systems for different joist spacings and pipe spacings. It also provides an even temperature profile across the floor through usage of a metal layer, preferably foil, which acts as a heat distribution layer. The system is easy to install, primarily from below the floor, and provides a reliable thermally conductive connection between the heating pipes and the heat distribution layer - i.e. the foil.

During installation, as much as possible of the continuous pipe 23 is held by the clips 22 in order to maximise the heat transfer from the pipe to the foil. Thus it is preferred that all possible straight lengths of pipe be held by clips, which latter may of course be cut to reduce their length, or bufted up to one another to increase their effective length, as circumstances dictate. Some of the bends could be catered for by curved pipe clips, but at a cost of slightly reduced operational flexibility.

Claims (21)

1. A method of installing underfloor heating in a suspended floor comprising a plurality of joists supporting a floorboard layer, said method comprising installing said floorboard layer on said joists, providing elongate pipe clips made of thermal material, and attaching said clips to the underside of said floorboard so that said clips are in contact with the underside of said floorboard and installing heating pipe to said clips to be supported thereby.

2. A method as claimed in claim I wherein a layer of thermally conductive material is installed against the underside surface of said floorboard layer, and said pipe clips are attached so that they are in contact with said layer of thermally conductive material.

3. A method as claimed in claim 2 wherein the floorboard layer is preinstalled with said layer of thermally conductive material.

4. A method as claimed in either one of claims 2 or 3 wherein the layer of thermally conductive material is installed in such a way as to cover the whole underside surface of said floorboard layer.

5. A method as claimed in either one of claims 2 or 3 wherein the layer of thermally conductive material is installed in such a way as to cover only that part of the underside surface of said floorboard layer which extends between the joists.

6. A method as claimed in any one of the preceding claims wherein two or more pipe clips are attached in series to enable continuous pipe support and thermal transfer.

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7. An underfloor heating system for a suspended floor comprising a plurality of joists supporting a floorboard layer, said system comprising a plurality of elongate pipe clips made of thermal material, said pipe clips having means whereby they may be attached to the underside of said floorboard layer, and one or more heating pipes located and supported by said clips.

8. A system as claimed in claim 7 further comprising a layer of thermally conductive material positioned against and in contact with, the underside surface of said floorboard layer whereby, when the pipe clips are attached to the underside of the floorboard layer, they make thermal contact with said layer of thermally conductive material.

9. A system as claimed in claim 8 wherein the thermally conductive material is metal.

10. A system as claimed in claim 9 wherein the thermally conductive material is aluminium.

11. A system as claimed in any one of claims 8 to 10 wherein the floorboard making up said floorboard layer is prefaced with said layer of thermally conductive material.

12. A system as claimed in any one of claims 7 to 11 wherein the pipe is made from flexible or semi-flexible material and is of sufficient length to extend from one inter-joist space to the next without a break.

13. A pipe clip made of a length of semi-rigid material, said length being shaped in profile to define an attachment section by which the pipe clip may be attached to a surface and an open-sided pipe retention section for retaining a length of pipe therein, and wherein the open side of said pipe retention section is orientated so as to allow the insertion of pipe therein when the pipe clip is attached to a surface.

14. A pipe clip as claimed in claim 13 wherein said retention section comprises an open channel into which a pipe can be pushed to secure same therein, and wherein the attachment section comprises a planar section which is attached against said surface to maximise heat transfer to said surface.

15. A pipe clip as claimed in claim 14 wherein the profile of said pipes is an open P-shape, with the leg of the P providing said planar attachment section, and the open top of the P providing said channel- shaped pipe retention section.

16. A pipe clip as claimed in any one of claims 13 to 15 wherein said semi-rigid material is a thermally conductive material.

17. A pipe clip as claimed in claim 16 wherein said thermally conductive material is metal.

18. A pipe clip as claimed in claim 17 wherein said pipe clip is fabricated from a sheet of metal which is bent to the required shape.

19. A pipe clip as claimed in claim 17 wherein said pipe clip is fabricated from extruded aluminium.

20. A pipe clip as claimed in any one of claims 13 to 19 wherein the profile of the pipe clip comprises a further open-sided pipe retention section for retaining a further length of pipe therein, and wherein the open side of said further pipe retention section is orientated so as to allow the insertion of pipe therein when the pipe clip is attached to a surface.

21. A system as claimed in any one of claims 7 to 12 wherein each of said elongate pipe clips is as claimed in any one of claims 13 to 20.