Static structures (e.g. – buildings) – Sheetlike element assembled parallel to existing wall,... – Element spaced from wall – ceiling – or floor and held by...
Reexamination Certificate
1999-05-04
2002-04-09
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Sheetlike element assembled parallel to existing wall,...
Element spaced from wall, ceiling, or floor and held by...
C052S508000, C052S404200
Reexamination Certificate
active
06367219
ABSTRACT:
The present invention relates to a building cavity assembly and, in particular, a building cavity assembly having a thermal break to prevent the development of cold spots acting as a gathering point for condensation.
Condensation can be a significant problem in buildings where warm, humid interior air meets the relatively cold surface of an exterior wall or roof (supercooling). The use of insulating material in the wall or roof cavity generally prevents loss of heat on the inner wall or roof skin as a result of a drop in temperature on the outer wall roof skin which is exposed to external weather conditions. However, cold spots may occur where there is a connection between the inner and outer skins such as those caused by roof fixing screws and support bars. The problem is particularly acute because of the relatively high conductivity of the metal screws and metal bars used in most roof and wall cavity assemblies. Much work has been directed to methods of preventing the transition of vapour across the cavity. Heavy gauge polythene has been used as a vapour barrier together with a liner panel. However, due to the numerous fixings which are necessary to fix the inner skin to the underlining purlins and to space the outer skin from the inner skin, holes and gaps are formed in the vapour barrier which diminishes its effectiveness. As a result, further improvements have been suggested such as the addition of a layer of gas permeable paper to reduce the exposure of the insulation to moisture from condensation.
Recently, an alternative solution to the condensation problem has been proposed. In most roof and wall cavity assemblies the basic construction consists of an inner and outer skin which are spaced from each other to provide a cavity to contain the insulation material. Generally, the inner skin is fixed to part of the building structure such as a roof and wall purlin and the outer skin is laid on support bars which are themselves mounted on brackets which space the support bar from the inner skin. For safety, the brackets are generally connected to the inner skin and the underlining roof structure such as the purlin. As the brackets and support bars are generally made from steel and the inner and outer skins from steel or aluminium, a thermal bridge is formed between the outer skin and the inner skin so that cold spots/cold bridging may be formed on the inner skin in the area of the bracket fixing. A solution suggested is to mount an insulating plastic cap on top of the bracket so that the insulating cap comes into contact with the support bar, thus providing a thermal brake between the inner and outer skins. Unfortunately, the system suffers from a number of drawbacks. Firstly, the thermal break is not complete and there is still some metal to metal contact between the metal support bar and the metal purlin below the plastic mounting so that condensation points still develop along the interior of the roof itself and allow moisture to collect. Secondly, it is necessary to lay the insulation round the brackets once they have been fitted to the inner skin causing damage to the insulating material and providing gaps in the insulation. Due to this, the proposed solution only compounds the problem and leaves significant gaps in the insulating material so that condensation forms on the inner roof skin despite the existence of the partial thermal break. Thirdly, the structure relies upon a snap-fit fixing between the support bar and the bracket and this may suffer from failure in extreme conditions causing roof damage and presenting safety hazards both during and after completion.
According to the present invention there is provided a building assembly comprising an inner and outer skin defining an insulating cavity, a support bar fixedly located in the cavity for mounting the outer skin thereon and an insulating spacer fixedly located between the support bar and the inner skin to provide a thermal break between the inner and outer skins, the support bar and the spacer being connected by means of a metal fixing device which passes through at least a part of the support bar and secures it to the spacer and fixes the spacer to the inner skin, wherein the fixing device includes insulating means to insulate it from the support bar and prevent any metal to metal contact therebetween.
Preferably, the insulating means forms a sheath around the fixing device at least where it may come into contact with the support bar. Preferably, a washer is located between the support bar and the fixing device to prevent contact of the fixing device with the part of the support bar against which it is urged, which washer includes an extension sheath to surround the part of the fixing device which passes through the support bar and thereby prevent any contact between the support bar and the fixing device.
Advantageously, by preventing any contact between the support bar and the fixing device, the fixing device does not act to conduct the temperature of the support bar onto the inner skin. In this way, it has been found that the heat loss measured as a U-value is significantly lower through the building assembly of the invention compared with one where the fixing device does not include insulating means or compared with composite panels. For instance, it has been shown that the U-value for a comparable composite panel or prior art building assembly without insulation means on the fixing device show U-values of approximately 0.45 whereas the building assembly of the invention shows a U-value of 0.30-0.38.
This comparison has been made with composites of standard thickness 45 mm and building assembly insulation material of conventional thickness of 80 mm. Thus use of the invention has been shown to significantly lower heat loss through roofs and walls.
Accordingly to a further aspect of the present invention there is provided a method of assembling a twin skin roof or wall cladding on a building comprising the steps of:
locating an inner skin over at least one underlying frame member such as a purlin;
locating insulating spacers at intervals on the inner skin at locations over the said underlying frame member;
locating an insulation layer such as glass wool on the said inner skin and over the said insulating spacers;
mounting an outer skin metal support bar on the insulating spacers; and
fixing the support bar to each insulating spacer and each spacer to the inner skin and underlying frame member with a metal fixing device; wherein the said metal fixing device includes insulating means to insulate it from the support bar and prevent any metal to metal contact therebetween.
Preferably, the insulating means forms a sheath around the fixing device at least where it may come into contact with the support bar. Preferably, a washer is located between the support bar and the fixing device to prevent contact of the fixing device with the part of the support bar against which it is urged, which washer includes an extension sheath to surround the part of the fixing device which passes through the support bar and thereby prevent any contact between the support bar and the fixing device.
Preferably, the fixing device insulating means is in the form of a washer with a socket extension thereto to thereby respectively insulate the head and sides of the fixing device from the support bar. The fixing device insulation means and the spacer can be made from a material of lower heat conductivity than that of the neighbouring parts. Preferably, the fixing device insulation means and spacer is plastic.
Preferably, the outer skin is secured to the support bar. The support bar is, typically, a metal Z-bar ie. a support bar with a Z-shaped cross-section which is of the type familiar to the man skilled in the art.
Preferably, particularly for wall cladding, the insulation layer such as glass wool is held in place over the spacers by means of a locating washer which is close fitting with the spacer and may be placed therearound to hold the insulation layer in position. This is particularly advantageous for wall cladding where the insula
Chavez Patrick J.
Friedman Carl D.
Jenkins & Wilson, P.A.
New Market Developments Ltd.
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