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 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.
It is an objective 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 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 introducing into said cavity an insulating membrane comprising:
(i) a reflective layer; and
(ii) a breathable textile layer.
Use of a textile layer instead of a polythene or other plastic sheet material to support the reflective layer provides improved insulation values and allows the building to breathe. Preferably the breathable textile layer comprises a non-woven textile.
In an alternative preferred embodiment the breathable textile layer comprises a woven textile.
In a particularly preferred embodiment the breathable textile layer comprises a fleece, and the fleece may be compressed.
The breathable textile layer may alternatively comprise felt or paper.
Preferably the textile layer is formed from a plastics material, which is particularly preferably selected from a group comprising:
or mixtures thereof.
Preferably the reflective layer comprises a metallised layer, which particularly preferably comprises aluminium.
Preferably the reflective layer comprises aluminium in the form of foil, laminate or a veneer, or aluminium deposited by vapour deposition.
In a particularly preferred embodiment the reflective layer is applied to the textile in the form of a vacuum vaporised aluminium coating in a form which does not materially reduce the permeability/breathability of the textile layer.
The metallised layer may optionally be coated with a protective layer to protect the metal surface from damp.
The reflective layer may incorporate perforations, preferably micro perforations.
In a preferred embodiment, the insulating membrane comprises a non-woven polypropylene fleece having an aluminium layer deposited onto the textile by vapour deposition.
Preferably the surface emissivity coefficient of the insulating membrane is in the range 0.01 to 0.25, and preferably the water resistivity is in the range 0.05 to 1 MNsg−1.
According to a second aspect of the invention there is provided a frame building insulated according to the method of the first aspect of the invention.