INSULATING MATERIAL

Abstract: A method of providing insulation between joists (31, 32) during building comprises unrolling a batt of mineral fibre which has, at least at its longitudinal edges, top (35, 45) and bottom (33, 43) layers. The bottom layer (33, 43) can be compressed to fit between joists, whilst the top layer (35, 45) extends across the joists, which adjacent strips (35, 45) abutting one another, to minimise cold bridging. The batt can be formed of two layers (33 and 35), (43 and 45) which may be manufactured by slitting a single web into two layers followed by winding the two layers together to form a roll.

Description: INSULATING MATERIAL The present invention relates to insulation formed of mineral wool provided in roll form and its use to insulate spaces between parallel joists and which minimises cold bridging effects. It is well known to provide insulation formed of mineral fibre wools, for instance glass wool and rock wool, in roll form. It is known to provide the roll such that the batt of mineral wool is of a suitable width for fitting between joists, for instance ceiling joists in lofts, positioned at standard distances for instance 400mm centres or 600mm centres. One product which has been available for some time comprises a 100mm thick and 570mm wide material wound into a roll. This provided adequate insulation to meet minimum requirements in the past. Building regulations have been increasing the requirements for minimum insulation and calculations of the insulation performance or "U values" must take into account the effect of thermal bridging at mortar joints, timber joists and studwork. This has meant that thermal bridging at ceiling joists should be minimised. One way of improving the U values is to use thicker insulation between the joists, for instance 150 or 180mm. However with the standard width roll the, even where the joists are of a lesser depth than the thickness of the insulation, cannot prevent thermal bridging. A roll formed of 150mm thick homogenous batt can be adequately pushed between the joists to fill the gap, but the upper portion, extending above the joists cannot overlap the joists adequately to provide insulation above the joist. Whilst increasing the thickness of a standard rectangular section batt to around 180mm would provide adequate U values, single thickness of loft insulation greater than the height of the joist results in the insulation being compressed in thickness when it is installed under bracing timbers which are typically nailed across the tops of the ceiling joists to aid roof stability. One solution to this problem is the Rockwool EnergySaver Super 150mm loft insulation. This consists of a double layer of mineral wool wound in a single roll. The bottom layer is 100mm thick, whilst the top layer is 50mm thick. The roll is unwound in the normal manner so that the bottom 100mm layer fits in the gap between joists. The top 50mm layer is subsequently loosened and re-positioned by moving it sideways so that it overlies a joist. Top layers of adjacent strips are positioned so that their longitudinal edges abut one another. Since the roll is narrower than the distance between the joist centres (in order that the bottom layer fits between the joists) at least one additional strip of the top layer is required to cover the entire area over the joists. The two step laying procedure is, in addition, time consuming. Another way of overcoming the problem of thermal bridging is disclosed in US-A-4303713. The insulating material is again provided as two components. A first relatively wide length of insulating material has elongated slits and notches which act as scores to allow the strip to be folded into a U-shaped configuration so as to line the gap between joists. The top arms of the U can be folded over to form flanges on each side which overlie the joists and, optionally, overlap with the corresponding flange on the strip positioned in the adjacent space between joists. Into the U-shaped cavity is unrolled a second insulating layer. This solution is even more complex than the preceding one as it requires separate positioning of two different types of material and furthermore the provision of slits and notches increases the manufacturing complexity. Another solution is disclosed in CA-A-1091886. A roll of material has a substantially T-shaped cross-section such that the base part of the T sits between the joists, whilst the top flange sections extend over the top of the joists. The T-shaped batt can be made either by cutting notches along the longitudinal edges of a rectangular section batt, or may be made by lying a wider strip centrally on top of a narrower strip. Both methods of manufacture are relatively complex. In addition, when the batt is wound in a roll, the ends are not smooth and can become damaged, thereby damaging the flange sections which may reduce the insulation properties. Flex-A-Batt is an insulation roll product made by Rockwool Limited and Rockwool International A/S which has improved flexibility such that when squeezed widthways, it retains some elasticity, exerting outwardly directed pressure, for instance on joists between which the batt is pushed. This allows a roll of material having a width equal to the distance between joist centres (400mm or 600mm, for instance) to be used to insulate between joists whereby improved properties of filling the gap and consequently of insulating performance are achieved. The present invention provides a product which is simple to manufacture, which is quick and straightforward to lay and which provides high insulation performance by minimising thermal bridging at joists. In a new method of providing insulation between sets of parallel joists having centre lines spaced Xmm apart and having a height Ymm (having a gap of depth Ymm between them) , a roll of mineral fibre wool which, when unwound and relaxed forms an elongated batt with substantially rectangular cross-section having width X to X + 40mm and a thickness of at least Y + 50mm and, along each longitudinal edge, comprises a top layer and a bottom layer defined by a split from the longitudinal edge to at least 15mm inboard from the edge, the bottom layer being Y ± 25mm thick and the top layer being at least 25mm thick, is unwound such that the batt lies parallel to the joists and generally centred along the midway between a pair of joists and with the said bottom layer facing the joists, the bottom layer is then compressed widthwise towards the batt centreline to push the bottom layer into the space between the joists and the top layer lies across the tops of the joists on each side of the batt such that the top layers of adjacent batts abut each other along a line generally level with the joist centrelines (ie in a plane passing through the joist centreline perpendicular to the plane of the batt) . The provision of the split between top and bottom layers in the insulating batt allows the bottom layer to be widthwise compressible independently of the top layer. This allows the bottom layer to be squeezed so as to fit between the joists, whilst the top layer is not compressed so that it is not forced into the gap between joists. The split between top and bottom layers must reach to at least 15mm in board of the longitudinal edge. The minimum width of the split depends, to an extent, on the difference between the thickness of the bottom layer and the height of the joists, as well as the difference between the relaxed width of the batt and the distance between joist centrelines, as well as the width of the joists themselves. The split has its smallest minimum when the thickness of the bottom layer is approximately equal to Y, the width of the batt is approximately equal to X and the joists are relatively narrow. The split can be provided by forming a single cut, for instance, generally parallel to the plane of the batt, along the longitudinal edges of a generally rectangular batt, before forming it into a roll. Alternatively, but less preferably, a notch or slot can be cut into the side. Alternatively, and preferably, top and bottom layers are entirely separate layers. These may be provided during manufacture either by aligning two batts of equal width and rolling them together. Alternatively a single batt can be slit during manufacture and immediately rolled. The bottom layer generally has a thickness as close to the height of the joist as possible. Preferably within 10mm of the joist height. Currently in new build houses in the UK, there are two standard heights, 75mm and 100mm. Consequently the bottom layer preferably has a thickness of 50-125mm, more preferably 65-110mm, for instance about 75mm or about 100mm. The top layer should have a minimum thickness such that when top layers of adjacent batts abutting one another overlie a joist, the thickness across the joist is adequate to minimise thermal bridging. A suitable minimum thickness is 25mm, whilst the top layer is preferably at least 50mm thick. The total thickness of the batt should generally be at least 100mm, more preferably at least 120mm, most preferably at least 135mm thick. It is preferable for the total thickness to be less than 175mm, most preferably less than 160mm. The width of the batt must be at least X, X being the distance between joist centre lines. This allows top layers of batts between adjacent gaps to abut one another without the top layer having to be translated (ie moved sideways) from its original position. The total width is generally no more than 30mm greater than X, preferably no more than 20mm greater than X, and preferably less than 10mm greater than X. The mineral wool may be glass wool or, more preferably, rock wool. The density should preferably be in the range 10 to 30 kg/m , more preferably in the range 19 to 27 kg/m . The wool preferably is flexible and resilient, so that it can be squeezed widthwise and retain elasticity so that it presses against the joists between which it is pushed. The invention is illustrated further in the accompanying drawings in which: Figure 1 is a section through a pair of joists showing the problem with provision of a uniform thick batt of mineral wool; Figure 2 is a section through a pair of joists showing the positioning of EnergySaver Super 150mm loft insulation; Figure 3 shows a section through two joists provided with insulation according to one embodiment of the present invention; Figure 4 represents a section through a pair of joists showing the provision of insulation according to a second embodiment of the invention; and Figure 5 is a perspective view showing the unrolling of a batt according to the first embodiment of the invention. Figure 1 shows the problem with one aspect of the prior art. A pair of joists 1, 2 having a height Ymm and a distance X between the centre lines are provided with a batt of insulation 3 which is, before being positioned between the joists, of substantially rectangular section having a width approximately Xmm (for instance 400 or 600mm) , and a thickness of, in this case, 150mm. The batt fills the gap 4 between the joists 1 and 2 but the top region 5 of the batt is compressed inwards at 6 so as to leave an air gap above the joist 2. Air gaps above or adjacent to the joists are not good practice as they result in cross ventilation between eaves thus reducing the insulation value. The thickness of the insulation along the abutting line 8 above the joist 1 is insufficiently thick and leads to thermal bridging. Figure 2 shows the solution to the problem provided in the prior art by EnergySaver Super 150mm loft insulation. The gap between joists 11 and 12, having height Ymm, is filled with a bottom layer of insulation 13, having a thickness of about Ymm. The relaxed width of the layer 13 is somewhat less than Xmm, but more than the distance separating facing sides of joists 11 and 12. The layer 13 adequately fills the gap 14 between joists 11 and 12. The batt 13 is provided as one layer of a double layer from a single roll, the upper layer being a batt 15 of the same material having the same relaxed width as the batt 13. The dual layer is provided by slitting a single, rectangular section batt parallel to the plane of the batt before winding it into the roll. The top layer 15 is unwound with batt 13 but is subsequently loosened and moved sideways so that it overlies joist 11. The total thickness of insulating material above the joist 11 at 18 is relatively high so that there is minimal thermal bridging. However as can be seen, in the adjacent gap between joists, 24, a batt of insulating material 23 is positioned, whilst the associated top layer 25 is again moved (to the left in the drawing) to overlie joist 12. This top batt 25 is positioned even further to the left relative to associated bottom layer 23 since the relaxed width of the batts 15 and 25 is less than the distance X between joists. Consequently at least one extra strip of top layer must be provided to complete the insulation. In addition the two- step fitting procedure, in which the top layers 15 and 25 have to be repositioned after bottom batts 13 and 23 have been pushed between the joists, is time consuming. Figure 3 shows one embodiment of the present invention and its use to insulate between joists 31, 32. The joists have a distance X between their centres lines, in this case 600mm. The joists are Ymm deep, in this case 75 or 100mm deep. The batt of insulation consists of a bottom layer 33 and a top layer 35 which, when relaxed, have the same width, namely 600mm. Both top and bottom layers have a thickness of about 75mm. Other thickness and combinations of thicknesses can be used. For instance where the joists are 100mm high, the top layer 35 may have a thickness of about 50mm and the bottom layer 33 may have a thickness of about 100mm. The density of both layers is the same and is in the range 19 to 27 kg/m . The two layers are wound together onto a roll and are positioned by unrolling along the gap between joists 31, 32. The bottom layer 33 is compressed inwardly to fit in the space 34 between the joists. The mineral wool is sufficiently resilient that the longitudinal edges of the bottom layer, 39, push against the joists 31 and 32. The top layer, 35, is not pushed between the joists. Since the relaxed width of the batt is about the same as the distance between the joist centre lines, the edge 36 of the top layer 35 overlies joist 32 up to approximately its centre line. The longitudinal edge 36 abuts the edge 46 of top layer 45 associated with bottom layer 43 of an adjacent batt 45 positioned between joist 32 and the adjacent joist (not shown) . As can be seen the total thickness of insulation above the joist along abutting edges 36 and 46 of top layers 35 and 45 is the thickness of the top layer itself, in this case 75mm. In this first embodiment, the slit, 40 between the bottom layer 33 and top layer 35 of the insulating batt extends across the entire area of the batt. In this embodiment, since the thickness of the bottom layer is about equal to the height of the joist 31, there is no air- gap or a minimal air-gap 47 at the corner of the joist thus minimising cross ventilation. Further since the total thickness of insulation above the joist at 48 is relatively high, thermal bridging is minimised. In an alternative embodiment of the invention shown in Figure 4, insulating material 50 is provided between joists 51 and 52 having Xmm centres and a height of Ymm (X and Y being, in this case, 600m and 100mm respectively) . The insulating batt 50, along its longitudinal edges, consists of a bottom layer 53 and a top layer 55 having between them a slit 60 formed by cutting the material parallel to the major face of the batt from the edge to a distance about 50mm inboard from the edge. This slit allows the bottom layer 53 to be compressed inwards to fit between joists 51 and 52 without causing the top layer 55 to be pulled inwards. Top layer 55 abuts top layer 65 of adjacent batt having bottom layer 63, so that the total thickness above the joist 51, shown at 58, is adequately thick to provide minimum thermal bridging. In this embodiment, the bottom layer 53 is about equal in thickness to the height of the joists 51 and 52. Consequently there is no air-gap or minimal air-gap 57 above the joist 51. Furthermore the thickness at 58 is greater than at 8 shown in Figure 1 illustrating the problem solved by the invention, even though the total thickness of insulation in this embodiment of the invention is lower. Thermal bridging is consequently lower in the invention than in the prior art. Figure 5 shows how the insulating material of the first embodiment is placed in position. A roll 30 of rock wool batt consists of two layers 33 and 35 wound together onto the roll. This dual layer product is for instance made by splitting a single layer into two before winding it to form a roll. The single layer may be made by the process described in DE-A-3703622 whereby the flexibility of the batt is controlled by partial crushing of the binder. The roll may be substantially as used for EnergySaver Super 150mm loft insulation. As the roll is unwound, bottom 33 provided on the outside of the roll, is positioned between joists 31 and 32, being squeezed to fill the gap 34 between the joists. Top layer 35, co-wound with bottom layer 33 lies on top of bottom layer 33 and, being the same width as the distance between joist centrelines, extends on each side to approximately the joist centreline. In Figure 5 insulation 43, 45 has already been positioned between the joist 32 and adjacent joist (not shown) . The insulation consists of top layer 45 and bottom layer 43 which has been squeezed between the joists. Top layers 35 and 45 meet at 48 which is level with the joist centrelines (that is vertically above joist centreline) .

Claims: CLAIMS 1. A method of providing insulation between sets of parallel joists (31, 32, 51, 52) having a centre line spaced Xmm apart and being Ymm high, in which a roll (30) of mineral fibre wool which, when unwound and relaxed forms an elongated batt with substantially rectangular cross- section having width in the range X to X + 40mm and a thickness of at least Y + 50mm, and which along each longitudinal edge comprises top layer (35, 55) and a bottom layer (33, 53) defined by a split (40, 60) from the said edge to at least 15mm in board of the edge, the bottom layer being in the range Y ± 25mm thick and the top layer being at least 25mm thick, is unwound such that the batt lies parallel to the joist centred generally along the line midway between a pair of joists, and with the said bottom layer facing the joists, the bottom layer is then compressed inwards towards the centreline to fit the bottom layer between the joists whilst the top layer is not compressed and lies on top of each of the pair of joists such that the top layers of adjacent batts abut each other generally level with the joist centrelines. 2. A method according to claim 1 in which the split between top and bottom layers extends at least 20mm, preferably at least 30mm, more preferably at least 50mm, inboard of the said longitudinal edge. 3. A method according to claim 1 or claim 2 in which the split (40) extends across the entire width of the batt. 4. A method according to claim 1 in which the bottom layer is in the range Y ± 10mm thick. 5. A method according to any preceding claim in which the width of the batt is in the range X to X + 10mm. 6. A method according to any preceding claim in which the total thickness of the batt is in the range 125 to 175mm, preferably in the range 140 to 160mm. 7. A method according to any preceding claim in which X is about 400mm or about 600mm and Y is in the range 75- 100mm. 8. A method according to any preceding claim in which the top layer is at least 50mm thick, preferably about 50mm or about 75mm thick. 9. A method according to any preceding claim in which the bottom layer is about 75mm or about 100mm thick. 10. A method according to any preceding claim in which the mineral wool consists of rock wool having a density in the range 19 to 27 kg/m .

Inventors: MARTIN RAYMOND WILLIAM, OSMOND CHRISTOPHER, MARTIN, RAYMOND, WILLIAM, OSMOND, CHRISTOPHER
Applicants: MARTIN RAYMOND WILLIAM, OSMOND CHRISTOPHER, ROCKWOOL LTD, MARTIN, RAYMOND, WILLIAM, OSMOND, CHRISTOPHER, ROCKWOOL LIMITED
Application year: 1997
Main classification: E04B1
IPC codes: E04B1, E04B9