24054 1 5
ENCAPSULATED THERMAL INSULATION
This invention relates to an insulation product formed of thermal insulation encapsulated in a film of metallised polyethylene, for use in thermally insulating buildings, for example as loft insulation.
Encapsulated insulation products in the form of elongated insulation halts are known, for installation between or over joists in lofts and other roof spaces. Known insulation balls are typically formed of a compressible fibrous thermal insulation material, such as glass mineral wool, rockwool, fibreglass wool or sheepswool, that is encapsulated in a sheet, sleeve or bag of a film material such as polyethylene (PE), polypropylene or polyester (e.g. Mylar.p Depending on the intended application for the insulation bats, the film over one or both of the major faces of the halt may be of a moisture-impervious material such as polyethylene, polypropylene or polyester, so as to provide a vapour barrier to prevent moisture from entering the fibrous insulation material, and/or may be of a pervious material. Alternatively, a continuous film of a moisture impervious material may be rendered pervious to moisture by perforating the film. Film perforation is also known to aid product roll up during manufacture and thickness recovery following product unrolling during use. In the arrangements where an insulation bait has one major face of a moisture-impervious film and the other major face of a moisture pervious film, the ball is generally configured so that the moisture impervious film faces the interior of the building and the moisture pervious film faces the exterior of the building.
Insulation baits are known that have a metallised film over one or both of the major faces. For example, WO-A-91/17326 discloses an insulation halt in which fibreglass insulation is sealed within a vapour proof container or bag, such as an airtight sack of the polyester material Mylar. According to this reference, the insulation sack may be silvered like a Mylar toy balloon, which will give it the extra benefit of all around reflective insulation. EP-A-O 839 968 discloses an insulation halt having aluminium deposited poly-films over both major faces. German Gebrauchmuster No. 8505179 discloses a mineral fibre insulation batt covered with a metallised polymeric facing adhered to the bats.
We have now found that a surprising improvement in roofspace thermal performance can be achieved from an encapsulated insulation bats, by encapsulating the insulation material in a metallised film having a low emissivity value (E value). By using a low emissivity metallised film, the roofspace thermal resistance benefit arising from the encapsulated insulation bait (as represented by the roofspace R value) is unexpectedly increased.
Accordingly, the present invention provides an encapsulated insulation product having two major faces, two side faces and two end faces, comprising a compressible fibrous insulation material encapsulated in a film, wherein the film over at least one major face is a metallised polyethylene film having an emissivity value E in the range from 0.05 to 0.25.
The insulation material is, for example, glass mineral wool, rockwool, fibreglass wool or sheepswool, and preferably is glass mineral wool.
We have found that the greater improvements in roofspace thermal resistance arising from the encapsulated insulation halt are achieved at lower E values for the metallised polyethylene film. Accordingly, it would technically be most desirable to use a metallised polyethylene film having a very low E value. However, in practice, manufacturing costs and tolerances may not always be able to produce metallised polyethylene films that consistently have very low E values, for example an E value below 0.07. Therefore, for practical and commercial reasons, we prefer that the metallised film has an E value in the range from 0.07 to 0.2, more preferably in the range from 0.1 to 0.2, and most preferably an E value of 0.2.
Figure 1 shows in cross-section an embodiment of an encapsulated insulation batt in accordance with the present invention. In this embodiment as shown in Figure 1, an insulation material 1 of glass mineral wool has a sheet of perforated metallised polyethylene film 2 over the top major face of the ball and a sheet of perforated unmetallised polyethylene film 3 over the bottom major face of the bats. The sheets 2 and 3 are heat-sealed together at the end faces (not shown) and at the side faces of the ball along seal 4. Metallised polyethylene film 2 consists of a polyethylene layer 2a in contact with insulation material I and of a layer of aluminium metallisation 2b over polyethylene layer 2a.
As a generality, an "emissivity value" or "E value" of a material describes its emissivity, and can take a value in the range from O to 1. If a material has an E value of 1, it is termed a black body, i.e. it absorbs heat and light energy and does not reflect anything back. A material that has an E value of O will reflect back all heat and light energy that it is exposed to. Emissivity therefore provides a measure of an insulation property of a material. The emissivity value of a material, and as referred to herein, can be determined in known manner.
The thermal resistance of many materials may be derived by dividing the material's thickness (expressed in m) by the material's thermal conductivity (expressed in W/mK), measured in known manner. Accordingly, the R value (expressed in m2K/W) of an insulation material of a particular thickness may be determined from its thickness divided by its measured thermal conductivity.
BS EN ISO 6946 assigns a single thermal resistance (R value) to the roofspace in pitched roofs where the insulation is at ceiling level ("roofspace thermal resistance" or "roofspace R value" as referred to herein). The value assigned depends on the make up of the roof. For common roofs (tiled, with felt or boards under the tiles; vented; bridged i.e. insulation laid between the ceiling joists), this assigned roofspace R value is 0.2 m2K/W.
Similarly, according to BS EN ISO 6946, R values may also be assigned or derived in respect of roof construction components such as plasterboard and any internal and external surfaces. The component R values of the particular roof construction (insulation / roofspace / plasterboard / surface resistances) may be summed in accordance with BS EN ISO 6946 to obtain a total roof R value for a particular roof construction. Thus, for different types of roof construction there will be a difference in the total roof R value depending on the roofspace R value assigned to the particular type of roof construction, all components being otherwise equal.
We have found that by using an encapsulated insulation material having a low E value film in accordance with the present invention, roofspace R values ranging from 0.29 to 0.43 m2K/W can be achieved, depending on the type of roof construction in which the product is used and the E value of the film. For example, we have found that by using encapsulated insulation having a film exhibiting an E value of 0.2, a roofspace R value of 0.29 m2K/W can be achieved in a traditional roof (tiled, with felt or boards under the tiles; vented; bridged), compared with the roofspace value of 0.2 assigned by BS EN ISO 6946. The difference in roofspace R values (0.29 m2K/W vs. 0.2 m2K/W) is the improvement attributed solely to the low emissivity surface of the encapsulated product according to the invention. Using encapsulated insulation having a film exhibiting an E value of 0.07, for example, we have found that a roofspace R value of 0.43 m2K/W can be achieved in an unbridged, unvented roof. These increases in roofspace R value translate into total roof R value improvements ranging from 3.4 % to 5.2 % for 100 mm thick encapsulation insulation (E = 0.2) or as much as 8. 6 % for 100 mm thick encapsulation insulation (E = 0.07), depending on the type of roof construction in which it is installed.
Films of silvered Mylar, whether silvered on the inside surface or the outside surface of the Mylar substrate, can exhibit low E values. However, silvered Mylar may be disadvantageous in terms of cost and tear resistance. By contrast, polyethylene is preferable as an encapsulation film material in terms of both cost and tear resistance, as well as in terms of its heat sealability. However, we have found that metallised polyethylene tends to have a poorer performance in terms of reaction to fire due to the layer of metallisation, and therefore may require the incorporation of a fire retardant additive to improve fire performance. The presence of fire retardants can diminish the clarity of the film, to the extent that a low E value may not always be practically attainable if the layer of metallisation is on the inside of the film, i.e. facing the fibrous insulation material. Moreover, the layer of metallisation can diminish the heat sealability of the polyethylene film if the layer of metallisation is on the inside of the film.
We have found that by providing a metallised polyethylene film having the layer of metallisation on the outside surface of the film and facing into the roofspace, a low E value film can be achieved that provides a surprisingly improved roofspace thermal resistance performance, whilst allowing the incorporation of a fire retardant to improve the film's fire performance, and which allows a good heat seal to be produced with the inside surface of the film. Accordingly, we prefer that the layer of metallisation on the polyethylene film is on the outside of the polyethylene layer, and preferably provides the external surface of the product.
The layer of metallisation may be any metal capable of providing the desired low E value for the film, such as aluminium or silver, applied to or deposited on the polyethylene layer in known manner, for example by vapour deposition. Preferably, the layer of metallisation is of aluminium to provide an aluminised polyethylene film. The E value for the film can be adjusted by varying the metal or thickness of the layer of metallisation. For example, a thicker metallisation layer will tend to result in a lower E value film. In a preferred embodiment, the metallisation layer is of aluminium and has a thickness in the range from 25 to 35 nanometres, so as to provide an E value of 0.2.
For certain applications, it may be desirable for the film to be a metallised polyethylene film over both major faces and the end and side faces. Preferably, the film over one major face is the metallised polyethylene film and the film over the other major face is an unmetallised film, preferably of polyethylene. In this embodiment, the encapsulation film is preferably formed of a metallised polyethylene film top sheet welded, heat-sealed, bonded or adhered to an unmetallised polyethylene film bottom sheet in known manner. Thus, the side faces and end faces may be formed of the metallised polyethylene film, the unmetallised polyethylene film, or both. Advantageously, the encapsulated product is convenient to handle and the film minimises any skin irritation that might otherwise be caused by the insulation material during handling.
In order to ensure that the top face of the product is pervious to moisture, the metallised polyethylene film over the top major face is suitably perforated. For applications where both the top and bottom face are required to be pervious to moisture, the films over both the top and bottom major faces of the product are perforated. Perforations, preferably across the width of the product, may be produced in known manner.
In order to afford acceptable fire performance to the product, the metallised polyethylene film may include a fire retardant additive. Similarly, if an unmetallised film of polyethylene is used to constitute the bottom face of the product, the unmetallised polyethylene film may also include a fire retardant additive.
If applicable, one or both films may include an anti-static additive. Preferably, at least the unmetallised film includes an anti-static additive.
The average thickness of the metallised polyethylene film may suitably be in the range from 10 to 50 1lm, more preferably in the range from 15 to 40 m, and most preferably is in the range of 20 to 30 lam.
The unmetallised film, if present, is preferably of polyethylene, for example a blend of HDPE and LLDPE polyethylene, and may be coloured in known manner, for example by master-batch colouration. The average thickness of the unmetallised film may suitably be in the range from 10 to 40 m, more preferably in the range from 10 to 20 Am, for example 15 m.
If desired, for example for installation applications to non-horizontal, especially vertical or near-vertical surfaces, the insulation material may be secured within the encapsulation film by adhering to the film using a suitable adhesive. For example, an adhesive may be used to fasten the film over one or both of the major faces to the insulation material. Preferably, however, the insulation material is not adhered to the encapsulation film.
It will be appreciated that the encapsulated product can be produced in any desired shape and size, according to the intended end use. Preferably, the encapsulated product has a nominal thickness, when in an uncompressed state, in the range from 90 to 250 mm, for example 150 mm or 200 mm. The width of the encapsulated product is preferably in the range from 300 to 600 mm, for example 370 mm or 570 mm, and the length is preferably in the range from 3 m to 10 m, for example 5.33 m or 4 m. The density for the encapsulated product is, for example, in the range from 9 to 13 kg/m3, for example 11 kg/m3.
For ease of transport and handling, the encapsulated product is preferably compressed, rolled up, and overwrapped with a sleeve in known manner, for example in a sleeve of polypropylene. The sleeve is removed before installation of the encapsulated product.
EXAMPLES
Encapsulated insulation halts of different thicknesses (100 mm; 150 mm; 200 mm; 100 mm +150 mm; 100 mm + 170 mm) and using aluminised polyethylene films having different E values (E = 0.2; E = 0.07) are installed in different roof constructions (vented; unvented) and laid horizontally either between the joists (bridged) or transversely over the joists (unbridged) and compared with unencapsulated insulation halts and with insulation halts encapsulated with film which does not have a low E value ( E = 0.3) of the same thicknesses.
The encapsulated halts are formed of low density glass mineral wool, having a 20-30 hum thick perforated aluminised polyethylene top sheet and a 15 lam thick perforated masterbatch coloured HDPE/LLDPE blend polyethylene bottom sheet. Top and bottom sheets are heat-sealed together along their edges to form the encapsulation film.
Thermal resistance R values (m2K/W) are shown in Table 1 below:
Table 1
Insulatio n thickn less (mm) 1 00 + 1 00 + 150 200 150 170 A. R value of insulation I (NOT ENCAPSULATED) [thickness / measured thermal conductivity value 0.044 W/mK] 2.273 3. 409 4.545 5.682 6.137 B. R value of internal/external surfaces Derived per Bs EN ISO 69461 0.14 0.14 0.14 0.14 0.14 C. R value plasterboard Known value per BS EN ISO 6946] 0.06 0.06 0.06 0.06 0.06 Comparative Example 1 (CE1) (Traditional roof- bridged, vented) : (NOT ENCAPSULATED) R value roofspace.
[assigned per BS EN ISO 6946] 0.2 0.2 0.2 0.2 0.2 Total roof R value [sum of 0.2+A+B+C] 2.673 3.809 4.945 6.082 6.537 Comparative Example 2 (CE2) (Traditional roof - unbridged, vented) (NOT ENC APSUL, (TED) R value roofspace [assigned per BS EN ISO 6946] 0.2 0.2 0.2 0.2 0.2 Total roof R value [sum of 0.2+A+B+C] 2.673 3.809 4.945 6.082 6.537 Comparative Example 3 (CE3) (Traditional roof- unbridged, unvented) (NOT ENCAPSULATED) R value roofspace [assigned per BS EN ISO 6946] 0.2 0.2 0.2 0.2 0.2 Total roof R value [sum of 0.2+A+B+C] 2.673 3.809 4.945 6.082 6.537 1 Comparative Example 4 (CE4) ; (Not low E roof - bridged, vented) I (ENCAPSULATED FILM E=0.3 R value roofspace, l l [assigned per BS EN ISO 6946] 0.2 1 0.2 0.2 1 0.2 1 0.2 Total roof R value l l l [sum of 0.2+A+B+C] 2.673 1 3.809 4.945 1 6.082 1 6.537 i. 1 I Example 1 l l I (Low E roof - bridged, vented) l I (ENCAPSULATED, FILM E=0.2) I R value roofspace l l l l l l [derived per BS EN ISO 6946] 1 0.29 1 0.29 1 0.29 1 0.29 1 0.29 otal roof R value l l l l l l [sumofO.29+A+B+C] 1 2.763 1 3.899 1 5.035 1 6.172 1 6.627 Improvement vs CE1, CE4 (%) 1 3 4 1 2 4 1 1.8 1 1.5 1 1.4
Example 2
(Low E roof- unbridged, vented) (ENCAPSULATED, FILM E=0.2 R value roofspace [assigned per BS EN ISO 6946] 0.3 0.3 0.3 0.3 0.3 Total roof R value I [sum of 0.3+A+B+C] 2.773 3.909 5.045 6.182 6.637 Improvement vs CE2 (%) 3. 7 2.6 2.0 1.6 1.5
Example 3
(Low E roof - unbridged, unvented) (ENCAPSULATED FILM E=0.2 R value roofspace, [derived per BS EN ISO 6946] 0.34 0.34 0.34 0.34 0.34: otal roof R value (sum of 0.34+A+B+C] 2.813 3.949 5.085 6.222 6.677: Improvement vs CE3 (%) 5.2 3.7 2.8 2.3 2.1
Example 4
(Low E roof - unbridged, unvented) (ENCAPSULATED, FILM E=0.07 R value roofspace [derived per BS EN ISO 6946] 0.43 0.43 0.43 0.43 0.43 Total roof R value [sum of 0.43+A+B+C] 2.903 4.039 5.175 6.312 6.767 Improvement vs CE3 (%) 8.6 6.0 4.7 3.8 3.5 The results show that encapsulated balls using aluminised PE film having an E value of 0.2 were able to provide an improvement in total roof R value of up to 5. 2 %, whereas halts using aluminised PE film having an E value of 0.07 were able to provide an improvement in total roof R value by as much as 8. 6 %, compared with unencapsulated insulation or insulation encapsulated with film which does not have a low E value. The surprising improvements achieved are attributed to the low E value of the film used. I