GB2451183A

GB2451183A - Improved thermal insulation

Info

Publication number: GB2451183A
Application number: GB0813082A
Authority: GB
Inventors: Hugo Brown; Rudolf Belanyi
Original assignee: Thermal Economics Ltd
Current assignee: Thermal Economics Ltd
Priority date: 2007-07-17
Filing date: 2008-07-17
Publication date: 2009-01-21
Anticipated expiration: 2028-07-17
Also published as: GB2451183B; GB0713874D0; GB0813082D0

Abstract

A method of insulating a frame construction building wherein a wall of said building comprises an outer cladding layer 22, a cavity 23, and a load bearing frame 20, 28, where said method comprises the step of suspending a breathable insulating membrane 24 within said cavity. An air gap is provided on both sides of the insulating membrane. The membrane (as shown in Fig 3) comprises at least one breathable reflective layer 2 and a breathable polymer layer 3. Preferably, the breathable polymer layer comprises a second breathable reflective layer, the first and second breathable reflective layers 2' being located on opposing faces of the breathable polymer layer 3'. The breathable polymer layer may comprise a microperforated polymer sheet. The breathable reflective layer(s) may comprise a metallised layer such as aluminium, where the aluminium is in the form of foil, laminate or a veneer, or is deposited by vapour deposition.

Description

IMPROVED THERMAL INSULATION

Field of the Invention

The present invention relates to an improved method and material for insulating buildings. It is particularly applicable, but in no way limited, to the insulation of framed structures including timber frame and steel frame buildings.

Background to the Invention

Buildings having a frame construction in which a supporting frame is constructed and then clad with brickwork, block work or other cladding material are well known.

There is generally a cavity between the external cladding and the frame, and insulating material is usually installed within the frame itself. The external and internal surfaces of the frame are covered by sheathing layers which retain this insulation in place. The internal surface of the frame carries a sheathing layer to take the internal building finishes. This type of building construction allows for a good deal of off-site pre-fabrication and can reduce construction time on-site significantly, when compared to conventional building methods. Frame buildings are thus becoming increasingly popular. The frame can be constructed from a range of materials including wood and steel.

As explained above, this type of building construction requires incorporation of a good deal of thermal insulation. In addition, a breathable waterproof barrier is required to prevent water penetration into the building interior whilst allowing water vapour to pass into and out of the structure.

A number of solutions have been developed to provide the necessary level of insulation whilst still allowing for the movement of water vapour. Traditionally, a vapour barrier is incorporated on the inner face of the inner sheathing layer and a water resistant breather membrane is positioned on the outer face of the outer sheathing layer. The frame volume is filled with an insulating blanket such as fibreglass or mineral wool. The outer, or breather membrane is designed to stop external water ingress but still allow the dissipation of water vapour. Most commonly it is made from a non-woven polymer textile. Micro-perforated sheeting has been tried but is generally not considered appropriate. The vapour barrier associated with the inner sheathing layer is designed to prevent or reduce water vapour ingress into the building. Typically this can be formed from a continuous polythene sheet.

A problem arises if improved insulation values are required. Since the frame is already packed with insulating material, a wider frame width would be required to achieve better insulation values. This would involve use of more frame material i.e. wood or steel, both of which are expensive. It would also involve changes to the production line where units are pre-fabricated. Both of these changes would lead to a significant increase in building costs.

An alternative would be to add an insulating membrane within the cavity. However, existing membranes have not performed well in this application and this route has generally been rejected by the building industry. Such membranes are usually formed from a laminate of aluminium foil and polyethylene, or some other sheet plastic material, and can include an air cushion layer. Whilst these membranes have good U values, they do not have the desired breathability for this type of application.

Use of an alternative type of membrane within the cavity is described in 0B2,382,827B (Thermal Economics Ltd). This describes the use of a breathable membrane having a reflective layer and a breathable textile layer positioned within the cavity against the sheathing layer on the external face of the frame. This provides some improvement in the thermal performance of the end product but, as Building Regulations become even more demanding in this regard, further improvements are desirable and will eventually become inevitable.

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

Summary of the invention

According to the present invention there is provided a method of insulating a building having a frame construction wherein the wall of said building comprises an outer cladding layer, a cavity, and a load bearing frame, said method comprising the step of suspending within said cavity a breathable insulating membrane comprising of:- (i) a breathable reflective layer (ii) a breathable polymer layer, wherein an air gap is provided on both sides of said breathable insulating membrane.

By suspending the insulating membrane within the cavity, spaced away from both the outer sheathing layer on the external face of the frame, and from the inner surface of the outer cladding layer, greatly enhanced insulation values are obtained.

Use of the reflective insulating membrane according to the present invention may be combined with use of a conventional breather membrane on the outer surface of the outer sheathing layer on the external face of the timber frame.

In an alternative embodiment, the insulating membrane comprises:- (i) a first breathable reflective layer; (ii) a breathable reinforcement polymer layer; and (iii) a second breathable reflective layer Use of a second reflective layer, located on the opposing face of the breathable polymer layer to the first breathable reflective layer, improves the insulation values of the method still further.

Preferably the air gap on one side of the breathable insulating membrane is greater than 5mm �20%.

Preferably the air gap on one side of the breathable membrane is greater than 10mm �20%, and more preferably in the order of 25mm �20%.

Preferably the breathable polymer layer comprises a microperf orated polymer sheet.

In a particularly preferred embodiment the breathable polymer layer further comprises a reinforcement layer.

Preferably the reinforcement layer comprises a grid or net of plastics material.

Alternatively the breathable polymer layer comprises a non-woven textile.

In a further alternative form of construction the breathable polymer layer comprises a woven textile.

Preferably the breathable polymer layer comprises a fleece, and preferably the fleece is compressed.

Alternatively the breathable polymer layer comprises felt or comprises paper.

Preferably the breathable polymer layer is formed from a plastics material, and the plastics material is selected from the group comprising:-polypropylene polyethylene polyester polyamide polycarbonate polyvinyl chloride or a mixture thereof.

Preferably the breathable reflective layer(s) comprises a metallised layer, preferably aluminium.

Preferably the aluminium is in the form of foil, laminate or a veneer, or is deposited by vapour deposition.

Alternatively the breathable reflective layer(s) is applied to the textile in the form of a vacuum vaporised aluminium coating.

Preferably the metallised layer is coated with a protective layer to protect the metal surface from damp/oxidation.

Preferably the breathable reflective layer incorporates perforations, and preferably the perforations are micro perforations.

In one preferred embodiment the insulating membrane comprises a non-woven polypropylene fleece having at least one aluminium layer deposited onto the textile by vapour deposition.

In a further preferred embodiment the breathable insulating membrane comprises a polymer sheet bonded to a reinforcing grid of polymer material, the membrane having sheets of aluminium foil bonded to both sides of the membrane, the membrane being microperforated, and the foil being protected by a plastics layer.

Preferably the surface emissivity coefficient of the breathable insulating membrane is in the range 0.01 to 0.25.

Preferably the water resistivity of the breathable insulating membrane is in the range 0.05 to 1 MNsg1.

Preferably said breathable insulating membrane is suspended at substantially the mid-point of the cavity.

The invention also extends to cover a frame building insulated according to the present method.

Brief Descri�tion of the Drawings Preferred embodiments to the present invention will now be more particularly described with reference to the following drawing in which:-Figure 1 illustrates diagrammatically an insulating membrane according to the present invention suspended, and displaced from, the outer sheathing layer of a portion of a frame building within the cavity between the frame and the outer brickwork cladding; Figure 2 illustrates a horizontal cross-section through a portion of frame construction according to the present invention; Figure 3 illustrates in diagrammatic format a first example of the layered construction of the insulating membrane; Figure 4 illustrates in diagrammatic format an alternative construction of the insulating membrane; Figure 5 illustrates a single cavity construction with a single foil face according to the

prior art;

Figure 6 illustrates a double cavity construction with a double-sided foil faced insulating membrane; Figure 7 illustrates a typical timber frame construction according to the present 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 practise but they are currently the best ways known to the applicant by which this can be achieved.

The building and construction industry is generally pre-disposed against the use of plastic-based reflective membranes in the cavities of frame construction buildings.

The term frame construction in this context is intended to encompass constructions in which a structure is formed from a structural or load bearing frame clad in some weatherproof material. The frame is generally constructed from wood or steel or other material as selected by the material specialist. The internal and external surfaces of the frame are covered with an internal sheathing material to take internal finishes, on the internal face, and with an external sheathing material on the outer face to retain insulation within the frame. There is inevitably a cavity between the frame and the cladding.

Currently, in a typical timber frame construction, the depth of the frame or structural studwork tends to be governed by the thermal insulation requirement rather than by the structural requirements. The current insulation (U-value) requirements are such as to increase the depth of the insulation (and studs) beyond the structural needs.

That is to say, the frame component of a timber frame building has a greater depth than is necessary to support the structure simply because a certain depth of insulation is required to meet the U-value stipulated in current Building Regulations.

Examples of this type of construction can be found in residential and small commercial buildings, portable buildings and caravans.

The pre-disposition against reflective membranes arises because of the poor breathablity of the prior art plastic-based membranes. Traditional full fill or partial fill cavity insulation is not acceptable in the cavity between the frame and the outer cladding of a timber frame construction, due to the interstitial condensation risk created. It has unexpectedly been discovered that by incorporating a reflective membrane suspended within the cavity between the cladding and the frame, but suspended away from both the external sheathing layer arid the internal surface of the cladding layer, much improved insulation values can be achieved with no detrimental effects. The addition of a breathable reflective insulating membrane, such as a double-faced microperforated foil, positioned in the middle of this cavity, adds sufficient thermal insulation to be able to maintain the minimum structural stud depth, thereby providing a substantial saving in material costs and additional

exploitable space.

This form of cavity insulation does not create an interstitial condensation risk as the microperforations in the foil allow water vapour to escape.

The nature and composition of the breathable insulating membrane are important for this method to be effective. In one form the membrane consists of two layers, a breathable textile layer and a breathable reflective layer. The textile layer can be made from a wide range of woven or non-woven fabrics, felt or paper. The key requirements are that this layer should be highly breathable as compared to polythene or other plastic sheet materials.

Alternatively, the reflective membrane may comprise a breathable textile layer sandwiched between two reflective layers.

The textile layer must have sufficient strength to support the reflective layer and to retain its integrity, even under damp conditions. Textiles made from man-made fibres have proven to be most suitable for this purpose and examples of suitable materials are polypropylene, polyethylene, polyester, polyamide, polycarbonate, polyvinyl chloride and mixtures thereof. It is not intended that this list should be exhaustive but rather give an indication of the type and breadth of fibres which can be used.

The breathable reflective layer is generally formed by a metalised layer on one or both sides of the polymer layer. The technology required to produce laminated reflective insulation is known, for example from WO 99/60222 (PIRITYI), the entire text of which is incorporated herein by reference. The metalised layer is typically formed from aluminium which can be in the form of a foil or veneer or may be formed by vapour deposition. The metalised layer must be coated with a layer of plastic, varnish or resin to protect the metal surface from damp and to protect it from oxidation. A tarnished or dull metal surface has much reduced reflectance properties.

In a preferred embodiment the metalised layer is applied to the textile layer in the form a vacuum vaporised aluminium coating. The technology required to deposit aluminium in this form is known to the person skilled in the art. A metalized layer deposited in this way does not materially reduce the permeability/breathability of the textile layer.

Where a foil or veneer is used, the metalised layer may be micro-perforated to allow the passage of water vapour through the membrane but prevent the ingress of liquid water. Again such micro-perforation technology is known.

Ar, example of one preferred membrane for use in this method consists of a compressed non-woven polypropylene fleece having an aluminium layer deposited onto the textile by vapour deposition and where the surface of the aluminium is protected from oxidation by a layer of lacquer. Such a membrane is illustrated diagrammatically in Figure 3. This illustrates a non-woven polymer textile layer 3 onto which a layer of aluminium 2 has been deposited. This metalised layer 2 is protected from oxidation, and from damp, by a layer of plastics material or resin lacquer 1.

One application of this invention is illustrated in Figure 1. This illustrates a section of a timber frame building comprising an inner timber frame 10, outer sheathing board 11, outer cladding 12 and a cavity 13. An insulating, reflective breather membrane 14 is installed within the cavity, dividing the cavity substantially into two separate cavities 13A and 13B. The foil surface of the breather membrane, and the division of the cavity into two smaller cavities, dramatically enhances the thermal value of the existing outer cladding.

By way of an example of the improvement gained by this new method, Figure 5 illustrates a breathable insulating membrane 44 placed within a 50mm cavity 43.

the insulating membrane is located directly against the outer face of the timber frame 40, with the single reflective face of the membrane facing the air gap of the cavity and facing the inner surface of the outer cladding 52, as directed by GB2,382,827B. This arrangement provides a typical R value in the region of 0.71 m2Kfw. Figure 5 thus represents the prior art arrangement.

In contrast, Figure 6 shows an example of the present method in which a breathable insulating membrane 54 is suspended substantially in the centre of a cavity 53 formed between a timber frame 50 and cladding 52. This arrangement provides a typical R value in the region of 2 x 0.71 or 1.42 m2K'W. This is a real and significant improvement over the existing method.

Whilst in these examples the breathable insulating membrane is shown suspended in a way that substantially bisects the cavity, this symmetry is not essential. What is essential is that there is a discrete air gap between both sides of the membrane and the structure to which the side is facing.

The air gap could be as small as 5mm and still produce beneficial effects. Typical air gaps are between 5mm to 25mm and more preferably between 10mm and 25mm.

In summary, there are two improvements made by working the present method.

A first improvement is obtained by suspending a reflective breathable insulating membrane within the cavity of a timber frame building, rather than securing it to the outer face of the timber frame. The second improvement is obtained by providing a breathable reflective layer or surface on both sides of the breathable insulating membrane.

Thus the method of the invention consists of the application of a thermally insulating breather membrane suspended within the cavity of a timber frame construction as illustrated, for the purpose of allowing the dissipation of water vapour from the construction, whilst protecting it from rain water ingress, and at the same time, improving the thermal insulation of the construction by virtue of a low emissive coating on one or both faces of the membrane.

In the example illustrated in Figure 1, the membrane 14 is suspended within the cavity by means of battens 18, which themselves are secured to the inner timber frame uprights. These battens serve both to displace the breathable membrane to substantially the mid-point of the cavity, and to provide securing points for wall ties 19 to tie the outer cladding to the timber frame. The breathable membrane is thus suspended approximately at the mid-point of the cavity, creating in effect two separate cavities.

As an alternative to the use of battens, a spacer could be used in combination with a conventional wall tie. This arrangement is shown in Figure 2. Wall ties 29 are used to tie the outer cladding layer to the frame. A spacer 31 having a broad flat face and feet or stand offs will, once pushed over an exposed wall tie, hold the insulation at a pre-determined distance from the outer face of the sheathing on the outside of the timber frame. In this example the breathable insulating membrane is held at substantially the mid-point of the cavity.

The nature and composition of one membrane for use in this application have been described. The preferred physical characteristics of this membrane consists of a non-woven manmade (polymer) textile, with a vaporised or laminated aluminium surface coating on one or both sides, which will have a surface emissivity coefficient ranging from 0.01 to 0.25.

The water vapour resistance tested to BS31 77:1959 lies in the range between 0.O5MNsg1 and 1.OMNsg1 and passes "EOSIN" resistance to water penetration test to BS4O1 6:1972.

A further type of membrane suitable for this application is shown in Figure 4. This illustrates a central liquid impermeable, liquid vapour permeable polymer layer 3'.

This can be formed from a solid continuous polymer sheet such as polyethylene or polypropylene sheet or one of the polymeric plastics materials described above.

Laminated onto both sides of this sheet are layers of aluminium 2', forming what is in effect a sandwich. Applied to the exposed outer surfaces of the two foil layers are layers of protective plastics material 1', such as polyethylene, or resin lacquer to prevent the foil from tarnishing by preventing exposure to oxygen or dampness.

In this form of construction, where aluminium foil is used, the membrane can be made breathable by microperforation. This technique is known per Se. By way of an example of the construction of a specific example of a suitable breathable insulating membrane, this may comprise a sheet of low density polyethylene reinforced by a grid or polypropylene. This is encapsulated, on both sides, by sheets of aluminium foil. The foil sheets are, in turn, protected by a polyethylene coating. The membrane is then microperforated to ensure breathability but at the same time preventing passage of liquid water.

If required, the polypropylene grid or reinforcement may be sandwiched between two sheets of polyethylene, the structure being heat bonded together. Other reinforcing layers can be used in this type of construction.

The use of a reinforcement layer is particularly advantageous since these insulating materials have to withstand handling and storage on building sites. The use of a grid or net made of a plastic material as a reinforcement layer is a particularly cost-effective solution to this problem.

A cross-sectional view, shown in Figure 2, also illustrates how the present method of insulation is applied. This illustrates a cladding layer 22 and a frame construction, shown as 30, separated by a cavity 23. The frame is constructed from metal studs 28 or timber studs 20, sandwiched between inner 25 and outer 21 sheathing layers.

Whilst both metal and wooden studs are shown in this diagram this is for illustration purposes only. Generally one material or the other would be used throughout one section. Insulation 26 is packed into the space between the sheathing layers. A breather membrane 24 having the construction and properties described above is installed within the cavity, spaced away from both the outer face of the outer sheathing layer and the inner facing of the cladding layer leaving a discrete cavity on either side of the breathable insulating membrane either in place of, or in addition to, a conventional water resistant breather membrane.

Figure 7 shows a typical timber frame in cross-section. The brick outer (60) is separated from the interior wall by an air cavity containing a foil-covered membrane (110). The interior wall is made up of a structural stud wall (100), fibreboard (70) and plasterboard (80). This construction is filled with mineral wool (90).

Su�plementary information and key for figures Figure 1 The Timber Frame' solution to achieving U = 0.30 W/m2K (Scotland) or U = 0.35 W/m2K (England and Wales) as required in the new Thermal regulations for 2002 without increasing the thickness of your timber frame construction.

Reference numeral Description

Rgure 1 17 Standard vapour barrier or Thermasheet' (RIM) reflective insulating vapour barrier Figure 2 20 Timber stud 21 Outer sheathing 22 Brick outer skin / cladding 23 Cavity 24 Water resistant breather membrane (location of Therma Breathe' (RIM)) Inner sheathing 26 Insulation between studs 27 Vapour barrier (continuous polythene sheet) 28 Metal stud

Claims

1. A method of insulating a building having a frame construction wherein the wall of said building comprises an outer cladding layer, a cavity, and a load bearing frame, said method comprising the step of suspending within said cavity a breathable insulating membrane comprising:- (i) at least one breathable reflective layer; and (ii) a breathable polymer layer, wherein an air gap is provided on both sides of the insulating membrane.

2. A method according to Claim 1 wherein a second breathable reflective layer is provided, the first and second breathable reflective layers being located on opposing faces of the breathable polymer layer.

3. A method according to Claim 1 or Claim 2 wherein the air gap on one side of the breathable insulating membrane is greater than 5mm �20%.

4. A method according to any preceding claim wherein the air gap on one side of the breathable membrane is greater than 10mm �20%.

5. A method according to any preceding claim wherein the air gap on one side of the breathable membrane is in the order of 25mm �20°Io.

6. A method according to any preceding claim wherein the breathable polymer layer comprises a microperf orated polymer sheet.

7. A method according to Claim 6 wherein the breathable polymer layer further comprises a reinforcement layer.

8. A method according to Claim 7 wherein the reinforcement layer comprises a grid or net of plastics material.

9. A method according to any of Claims 1 to 5 inclusive, wherein the breathable polymer layer comprises a non-woven textile.

10. A method according to any of Claims 1 to 5 inclusive, wherein the breathable polymer layer comprises a woven textile.

11. A method according to Claim 9 or Claim 10, wherein the breathable polymer layer comprises a fleece.

12. A method as claimed in Claim 11, wherein the fleece is compressed.

13. A method according to any of Claims 1 to 5 inclusive, wherein the breathable polymer layer comprises felt.

14. A method according to any of Claims 1 to 5 inclusive, wherein the breathable polymer layer comprises paper.

15. A method according to any of Claims 1 to 12 inclusive, wherein the breathable polymer layer is formed from a plastics material.

16. A method according to Claim 15, wherein the plastics material is selected from the group comprising:-polypropylene polyethylene polyester polyamide polycarbonate polyvinyl chloride or a mixture thereof.

17. A method according to any preceding Claim, wherein the breathable reflective layer(s) comprises a metallised layer.

18. A method according to Claim 17, wherein the metallised layer comprises aluminium.

19. A method according to Claim 18, wherein the aluminium is in the form of foil, laminate or a veneer, or is deposited by vapour deposition.

20. A method according to Claim 18, wherein the breathable reflective layer(s) is applied to the textile in the form of a vacuum vaporised aluminium coating.

21. A method according to any of Claims 17 to 20, wherein the metallised layer is coated with a protective layer to protect the metal surface from damp/oxidation.

22. A method according to any preceding Claim, wherein the breathable reflective layer incorporates perforations.

23. A method according to Claim 22, wherein the perforations are micro perforations.

24. A method according to Claim 9 or any claims dependent on Claim 9, wherein the insulating membrane comprises a non-woven polypropylene fleece having at least one aluminium layer deposited onto the textile by vapour deposition.

25. A method according to any preceding Claim wherein the surface emissivity coefficient of the breathable insulating membrane is in the range 0.01 to 0.25.

26. A method according to any preceding Claim wherein the water resistivity of the breathable insulating membrane is in the range 0.05 to 1 MNsg1.

27. A method according to any preceding claim wherein said breathable insulating membrane is suspended at substantially the mid- point of the cavity.

28. A frame building insulated according to the method of any preceding Claim.

29. A method of insulating a building substantially as herein described with reference to and as illustrated in Figures 1 to 4 and 6 and 7.

30. A frame building substantially as herein described with reference to and as illustrated in Figures 1 to 4 and 6 and 7.