GB2326652A - A method for installing underfloor insulation - Google Patents

Description

IMPROVED UNDERFLOOR INSULATION Field of the Invention The present invention relates to an improved method and apparatus for insulating floors. It is particularly applicable, but in no way limited, to the insulation of pre-stressed concrete floors.

Background to the Invention Pre-stressed concrete floors are used extensively by the construction industry in both commercial and domestic premises. Whilst this type of floor construction offers a number of advantages in terms of speed of construction and cost, the resultant floor has limited thermal insulation properties which are determined by the thickness and type of material used. That is to say a pre-stressed concrete floor has an inherent U value which can only be altered by adding further layers of insulation. There is an everincreasing pressure to improve the thermal insulation property of floors and this is reflected in tougher building regulations. In the case of pre-stressed concrete floors this is typically achieved by adding one or more layers of insulating material on top of the floor once it has been laid. However, since construction continues after the floor has been installed, this insulation is prone to damage.

Alternatively, concrete with improved insulating properties can be used.

However, this tends to adversely effect the other properties of the floor, such as its strength, and also results in a considerable increase in cost which the customer is unwilling to bear.

It is an object of the present invention to overcome or mitigate some or all of these problems.

Summary of the Invention According to a first aspect of the invention there is provided a method of constructing a floor comprising the steps of : (i) constructing a perimeter wall up to underfloor level; (ii) laying an insulating membrane across the area onto which the floor is to be laid, extending the insulating membrane over and down the external face of the perimeter wall; (iii) tensioning the insulating membrane across the floor void and securing the insulating membrane to the perimeter wall at intervals using securing clips; (iv) laying supporting beams across the span between opposing perimeter walls such that the beams rest on the perimeter wall and thus on the insulating membrane; (v) laying sections of floor across the beams to provide the completed floor.

The resulting insulation comprising the membrane and trapped air is highly effective and is protected from damage by the floor itself. Preferably the floor is a prestressed concrete floor, but the method works successfully with other types of floor.

Preferably the insulating membrane comprises a plastics film laminated with aluminium foil.

In a particularly preferred embodiment the insulating material comprises polyethylene film reinforced with a polypropylene bird net laminated with low emissivity aluminium foil.

Advantageously insulating membrane is micro-perforated to allow accidental spillage or dampness to dissipate.

According to a second aspect of the invention there is provided a retaining clip suitable for securing an insulating membrane across the top of a wall skin, said clip comprising a first arm and a second arm, a first end of the first arm being interlinked with a first end of the second arm, the two arms being resiliently biased apart at an angle greater than 0 and less than 1800, the clip further comprising detent lugs at or near the second end of each arm and a further detent lug at or near the interlinking point of the two first ends of the arms, the detent lugs being adapted to grip the insulating material against the wall skin, the clip being so sized and shaped such that when the second ends of the two arms are pressed towards each other in use, against the natural biasing action of the clip, the clip is adapted to fit over the top of the wall and on release, to grip the membrane to both sides of the wall.

Preferably the first and second arms and the associated detent lugs are formed from a single piece of wire. This simplifies construction considerably and reduces cost.

The degree of biasing force is determined by the properties of the wire.

Preferably the angle between the first and second arms is substantially 90 .

Particularly preferably the detent lugs associated with the second end of the arms incorporate a portion at their lowermost in use end which extends away from the wall to form a handle which enables the two arms to be pressed together.

Brief Description of the Drawings The present invention will now be described with reference to the following drawings in which: Figure 1 illustrates diagrammatically an insulating membrane stretched over a corner of a perimeter blockwork inner cavity skin according to the first aspect of the invention and held in place by clips according to the second aspect of the invention; Figure 2 illustrates beams spread across the walls ready to accept pre-stressed concrete flooring slabs; Figure 3 shows a perforating tool being used to cut small holes in the mid span of a sheet of insulation to facilitate the rapid drainage of heavy rain; Figure 4 illustrates a typical arrangement where soil pipes or other piping protrude through the insulating membrane; Figure 5 shows a cross section through a section of floor prior to installation of the beams and concrete blocks but with the insulation in place; Figure 6 shows the detail at a lap joint; Figure 7 shows a perspective view of a retaining clip according to the second aspect of the invention; Description of the Preferred Embodiments The preferred embodiments of the present invention will now be described by way of example only. They are not the only ways in which the invention can be put into practice but they are currently the best ways known to the applicant by which this can be achieved.

The first aspect of the invention relates to a method of insulating a suspended precast concrete floor. These floors are typically constructed by building a perimeter blockwork or brickwork inner cavity skin wall up to underfloor level, spanning beams between opposite perimeter walls or intermediate upstands then laying concrete blocks in place across the beams. According to the present method, insulation is installed by a special method prior to laying the spanning beams. Referring to Figure 1, this shows a corner section of a perimeter blockwork inner cavity skin wall 10 with FLOORTHERM (TM) insulation 11 laid in place. The insulation is held in place by retaining clips 12 which have been specifically developed for this purpose (see below).

This aspect of the invention is best described by way of the installation instructions as follows:1. Roll out the chosen width of Floortherm MP "on the ground with the first roll at the end gable a minimum of 200mm (8") over the end gable perimeter wall (see fig.

1.) 2. Cut roll to size allowing a minimum of 200mm to project past outer edge of perimeter walls 10 with material over walls and resting on ground.

3. To facilitate the rapid drainage of heavy rain fall use the "Floortherm Perforating Tool" 14 supplied (see fig.3) to create holes within the reinforcement matrix at 500mm (20") centres across the width of the roll only at the mid-span between the supporting walls.

4. Fix butyle tape to the free edge of the first roll over the full length approximately 75mm (3") from the edge (see detail at lap joint) and remove backing paper.

5. Roll out a second width of material on ground over perimeter walls and cut to length as first roll width.

6. Lap second roll width a minimum 150mm over second roll width over the full length of the rolis and securely seal by pressing onto butyle tape (see detail at lap joint).

7. Secure one end of the two adhered rolls to one of the perimeter walls with the clips as shown in fig.1 allowing 100mm to dress down into cavity. The Floortherm Wire Wall Clips, 12 should be bent along the centre wire downstand to secure the Floortherm tightly onto the perimeter wall with the two downstand legs to the inside as shown. The wire clips should be a maximum 500mm centres (3 to a 1500mm roll and 5 to a 1980mm wide roll) with a clip always on the lap as shown in fig 1.

8. With one operative holding the material secure on the wire clips at one end a second operative tensions the roll widths over the outer perimeter wall 1 0A and clips the material to this wall with the clips as given. The downstand legs of the clips create a minimum 25mm air gap between the underside of the precast floor and the top of the Floortherm. The material can be allowed to sag in the middle creating an even larger air gap which will in fact further enhance the thermal resistance calculated by the BRE for a 25mm air gap! (see fig. 2).

In general the underside of the Floortherm 11 should be a minimum of 20mm (3/4") off the ground/concrete blinding and the area under the Floortherm MP should be ventilated in the normal way.

9. The third and all but the last roll should be laid over the perimeter walls and on the ground, taped with the butyle tape, cut to size and clipped to the perimeter walls all as given in paragraphs 1 to 7.

10. The last width of Floortherm MP should be installed as above but also clipped to the end gable wall with the "Floortherm Wall Clips" as shown in fig. 1.

11. Where soil pipes or other piping etc. protrude through the Floortherm make a cross-cut incision in the material to accommodate the diameter of the pipe. As this incision will normally become elongated as the material is tensioned and secured to the walls place a suitable "patch" of Floortherm carefully over the pipe and adhere it to the Floortherm with aluminium tape after the material is tensioned and clipped. The "patch" should have a neat cross-cut incision to suit the pipe and be adhered to the pipe with aluminium tape to close any holes (see fig.4).

12. When the installation is complete the operative should ensure that a maximum of 100mm (4") of Floortherm is protruding into the cavity. Any excess material should be cut-away.

13. After the Floortherm MP is fully fixed and sealed over the total ground floor area the beam and block floor should be installed as shown in the detail given on page P2. Great care should be taken by the installers not to damage or tarnish the Floortherm MP membrane in any way during the installation of the floor.

It will be appreciated that any suitable insulating sheet material can be used to create the insulating membrane in this method. It is preferred that the membrane comprises a plastics film laminated with aluminium foil. Preferably it comprises polyethylene film reinforced with a polypropylene bird net laminated with low emmisivity aluminium foil.

Microperforations in the membrane allow accidental spillage or dampness to dissipate through the membrane.

Various forms of clip can be used and any clip capable of holding the insulating membrane in place over the perimeter wall or intermediate upstands until the floor is laid will suffice.

The second aspect of the present invention concerns retaining clips suitable for securing an insulating membrane across the top of a wall skin. These clips have to hold the insulating material in place across the top and partly down each side of a stub wall without damaging the membrane. Importantly, they must be quick and easy to install and be capable to accommodating slight variations in wall width whilst still gripping and retaining the membrane. In order to achieve this objective a new clip has been devised as illustrated in figure 7. The clip consists of two arms 31 and 32 linked together at one end at a point 33. At the end of each arm furthest from the linking point there is a detent lug 34, 35 adapted to grip the membrane to the wall. In this example the two arms are resiliently biased apart at approximately 90" to each other and the lugs are at an angle of approximately 90" to the longitudinal axis of the arm. Other angles between the two arms are possible and in principle any angle between 0 and 180 could be used.

The bottom or lowermost-in-use end of each lug is bent back on itself in the plane of the arm and away from the linking point to form extensions 36, 37. These provide two important features. First, they provide a smoothly contoured finish at the bottom of the lugs which protect the membrane from damage. Secondly, they provide handles with which to grip the ends of the arms so that the two arms can be urged together against the natural biasing action of the clip.

A further detent lug 38 is provided at the linking point 33 which again is at substantially 90" to the axis of the respective arms.

It will be appreciated that the wall and membrane fit within the notional lines A A' and B B' as shown in figure 7. In order to achieve this the arms of the clip are forced together against the natural bias in the direction of the arrows shown, to increase the distance between planes A A' and B B'. This enables the clip to be slipped over the wall and membrane and when released it grips the membrane tightly against the wall.

In a preferred embodiment the clips are made from one continuous length of wire, the downstand 38 being formed by looping the wire down as shown in the inset. In this example the clips can also be bent along the centre wire downstand to secure the insulating membrane tightly onto the perimeter wall with the two downstand legs to the inside as shown in figure 1. It must be stressed that this is only one possible form of construction. Other one piece and two piece constructions are equally possible and it is intended that this specification should cover all variants which provide the above characteristics.

The biasing force in the clip can be created by the natural resistance and flexibility in the clip material or by a biasing component or resilient member such as a spring or spring clip.

KEY FOR FIGURES Figure 1 12 Clip holds Floortherm on block and forms minimum air gap under floor.

Floortherm clips at maximum 500 mm centres.

11 Floortherm sags between supports 10 Perimeter blockwork inner cavity skin 9 Use Floortherm clip to secure lap joint at perimeter blockwork 8 Floortherm 'dished' into comers.

7 Floortherm dressed down blockwork wall to insulate ground floor Figure 2 Detail of Floortherm MP under Standard Beam & Block Concrete Ground Floor Figure 3 Floortherm perforating tool cutting small holes at 500 mm centres in d span to facilitate the rapid drainage of heavy rain Figure 4 41 Flowtherm patch taped to Flowtherm floating membrane and also secured around pipe with T.E. aluminium tape.

42 Pipe protrudes through Flowtherm Figure 5 51 Floortherm MP 52 Floortherm MP maximum 100 mm protruding into cavity. Excess material to be cut away 53 20 mm minimum Figure 6 61 Seal joint securely with 25 mm special butyle tape along full length of lap Figure 7 39 Inset

Claims (11)

1. CLAIMS 1. A method of constructing a floor comprising the steps of (i) constructing a perimeter wall up to underfloor level; (ii) laying an insulating membrane across the area onto which the floor is to be laid, extending the insulating membrane over and down the external face of the perimeter wall; (iii) tensioning the insulating membrane across the floor void and securing the insulating membrane to the perimeter wall at intervals using securing clips; (iv) laying supporting beams across the span between opposing perimeter walls such that the beams rest on the perimeter wall and thus on the insulating membrane; (v) laying sections of floor across the beams to provide the completed floor.
2. 2. A method according to claim 1 wherein the floor is a pre-stressed concrete floor.
3. 3. A method according to claim 1 or claim 2 wherein the insulating membrane comprises a plastics film laminated with aluminium foil.
4. 4. A method according to claim 3 wherein the insulating material comprises polyethylene film reinforced with a polypropylene bird net laminated with low emissivity aluminium foil.
5. 5. A method of constructing a floor according to any preceding claim in which the insulating membrane is micro-perforated.
6. 6. A method of constructing a floor substantially as herein described with reference to and as illustrated in any of the accompanying drawings.
7. 7. A retaining clip suitable for securing an insulating membrane across the top of a wall skin, said clip comprising a first arm and a second arm, a first end of the first arm being interlinked with a first end of the second arm, the two arms being resiliently biased apart at an angle greater than 0 and less than 180 , the clip further comprising detent lugs at or near the second end of each arm and a further detent lug at or near the interlinking point of the two first ends of the arms, the detent lugs being adapted to grip the insulating material against the wall skin, the clip being so sized and shaped such that when the second ends of the two arms are pressed towards each other in use, against the natural biasing action of the clip, the clip is adapted to fit over the top of the wall and on release, to grip the membrane to both sides of the wall.
8. 8. A clip according to claim 7 wherein the first and second arms and the associated detent lugs are formed from a single piece of wire.
9. 9. A clip according to claim 7 or claim 8 wherein the angle between the first and second arms is substantially 90".
10. 10. A clip according to any of claims 7 to 9 inclusive wherein the detent lugs associated with the second end of the arms incorporate a portion at their lowermost in use end which extends away from the wall to form a handle which enables the two arms to be pressed together.
11. 11. A clip substantially as herein described.