GB2486296A

GB2486296A - Method of lowering the thermal conductivity of a building roof

Info

Publication number: GB2486296A
Application number: GB201115269A
Authority: GB
Inventors: Dennis Anthony Clark
Original assignee: THERMOTEC ROOFING SYSTEMS Ltd
Current assignee: THERMOTEC ROOFING SYSTEMS Ltd
Priority date: 2010-12-10
Filing date: 2011-09-05
Publication date: 2012-06-13
Anticipated expiration: 2031-09-05
Also published as: GB201115269D0; GB201021005D0; GB2486276A; GB2486296B

Abstract

The method is for use with a building roof with at least one spaced pair of rafters 1 which receive a glazing panel of predetermined thickness which is secured to the rafters by at least one retaining member 2. The method comprises removing the retaining members, removing the glazing panel and replacing this with an insulating panel 5 of significantly greater thickness than the predetermined thickness, preferably twice the predetermined thickness, and refitting the retaining members to retain the insulating panel on the rafters, wherein the insulating panel has upper and lower skins with thermally insulating material in between and an edge portion 5a of the predetermined thickness. The edge portion may be integral or may be provided by an aluminium frame in which the insulation panel is mounted. The skins of the insulating panel may be aluminium and the core may be expanded polyurethane.

Description

METHOD OF LOWERING THE THERMAL CONDUCTIVITY OF A BUILDING

ROOF

Field of the Invention

This invention relates to a method of lowering the thermal conductivity of a building roof.

Background to the Invention

Glazed conservatories and porches have been popular additions to houses for some years, but their construction has tended to limit their usability at least at certain times of the year. In the UK, these types of structures are ex-empted from planning and building regulations if certain criteria are met, such as size and structural separation from the house so that it is considered essen- tially temporary. The result is that the structures are cheaper and more light-weight than conventional regulated buildings, and typically do not meet modern standards for thermal insulation. In the winter, heat losses through the glazed Is roof in particular mean that it is not economic to keep the conservatory warm, while in the summer and with the sun fully on the structure, it can become too hot for comfort inside.

Various proposals have been made to use double-walled plastics glazing panels in place of glass to try to increase the thermal insulating properties, but these still fall far short of currently required standards for building roof insula-tion. There have also been proposals to modify the supporting structure to permit double layers of such panels, or even spaced-apart layers, and while these undoubtedly offer better thermal insulation than a single layer, they are still not sufficient significantly to improve the usability of the structure. In addi-tion, they require specially modified supports to accommodate the double or multiple layers, which means that it is generally not possible to use such sys-tems to improve existing structures.

Thermal insulating panels are also well known. US2003233796A1 for example, discloses panels having an insulating core sandwiched between two outer panels. The insulating panels are mounted on the conservatory by way of a custom hanging rail fixed to the wall of the supporting building, the opposite end being supported on an outer wall of the conservatory I sun room. The pan-els are joined together by a "tongue and groove" system providing a degree of longitudinal support along the joint between the panels US506250A discloses an insulating panel having a longitudinal cut-out profile, slidable onto one edge of a corresponding rafter. Using this panel, it would not be possible to simply replace the existing panels as the roof support-ing structure would also have to be replaced with a plurality of corresponding rafters.

GB2455586A discloses an insulating tile constructed from two layers of GRP between which is sandwiched a layer of insulating material. The tiles are configured to simulate the appearance of a traditional roof while being of sub-stantially reduced weight. The existing rafters, beading and retaining members are used to mount the tiles on the building roof. The tiles are of the same thick-ness as the glazing panels they replace, hence there would be no appreciable reduction in thermal conductivity.

Is US3913292A discloses a type of "stepped" ceiling panel having edge portions significantly thinner than the remainder of the panel. The panels are orientated in such a way that they interlink together removing the need for longi-tudinal supporting members between the panels. Custom lateral supporting members are however disclosed as being necessary to support the end of the panel fixed to the supporting building wall.

The insulating panels disclosed in the prior art documents cited above undoubtedly offer some advantages over standard glazing panels. Their use would be somewhat limited by the requirement to fit additional supporting ele-ments, with the exception of GB2455586A, which uses the existing roof support structure.

There is currently no satisfactory solution which enables significantly thicker insulating panels to replace glazing panels of pre-determined thickness without modifying the existing roof structure.

Summary of the Invention

According to the invention, there is provided a method of lowering the thermal conductivity of a building roof of the type comprising at least one spaced pair of rafters receiving between them at least one glazing panel of pre-determined thickness, and at least one retaining member co-operating with the rafters to hold the longitudinal edge of each of said glazing panels on said raft-ers, the method comprising: removing the or each retaining member from an existing building roof; removing the or each glazing panel from an existing building roof and replacing said glazing panel or panels with at least one insulating panel of sig-nificantly greater thickness than said pre-determined thickness, having upper and lower skins and thermally insulating material therebetween, said insulating panel having an edge portion of said pre-determined thickness, wherein the lower face of said edge portion sits on the upper face of said rafters and the up-per face of said edge portion is engage by said retaining members; re-fitting said retaining members to engage said edge portions to retain said insulating panels on said rafters.

The particular configuration of the insulating panel allows for panels of at Is least twice as thick as the thickness of existing glazing panels to be fitted to a conservatory roof without having to modify the existing roof structure. The edge portion of pre-determined thickness may be integral to the insulating panel but it could also be part of a receiving frame into which the insulating panels mount. It will be appreciated that any form of edge portion of pre-determined thickness could alternatively be used.

In accordance with the invention, an existing glazed conservatory, for example, can be converted into a sun-room meeting current standards of ther-mal efficiency by replacing at least the major part of the glazing panels in the roof with lightweight insulating panels.

Brief Description of the Drawings

In the drawings, which illustrate exemplary embodiments of the invention: Figure 1 a sectional end elevation of a portion of a timber rafter with insu-lating panels fitted; Figure 2 is a corresponding view to that of Figure 1, but showing an ex-truded aluminium rafter; Figure 3 is a similar view of a timber hip rafter with the panels fitted; Figure 4 is a view of a portion of a conservatory building illustrating the roof structure with insulating panels fitted; Figure 5 illustrates another embodiment and shows a sectional end ele-vation of a portion of a timber rafter with a mounting frame fitted to receive and retain an insulating panel; Figure 6 is a corresponding view to that of Figure 5, but showing an ex-truded aluminium rafter; Figure 7 shows a sectional end elevation of a timber hip rafter with mounting frame and insulating panels fitted.

Detailed Description of the Illustrated Embodiment

Figure 1 illustrates a conventional timber conservatory is constructed with timber rafters 1 on which the glass or other glazing panels are mounted by laying the panels on the upper surfaces of the rafters, with suitable resilient sealant beading between, and then securing a capping strip 2 over the gap be-Is tween adjacent sheets. The capping strip carries resilient sealant beading 3 along its underside to engage the glazing panels to hold them in place and to prevent ingress of water which could damage the timber. The capping strip can be simply pinned into the rafter with pins 4. In accordance with the invention, the glazing panels are replaced with insulating panels 5 which are typically formed as hollow bodies fabricated from aluminium sheet, into which are insert-ed expanded polyurethane insulating boards (or other insulating material), the panels then being sealed to enclose the insulating material. The panels 5 have a general thickness significantly greater than the glazing panels they replace, for example being at least twice as thick, in order to achieve insulation values in accordance with current building regulations. However, in order to enable the panels to fit with existing structures, the panels 5 are constructed with a mar-ginal portion 5a of the same thickness as the glazing panels they replace, along at least the sides thereof which fit on to structural members of the building.

Figure 2 illustrates the equivalent view for an extruded aluminium rafter 6, which is essentially an inverted T-shape, with the arms of the T formed into a shallow tray 7 to conduct any water which penetrates the joint away to the gut-tering running along the lower edge of the roof. The insulating panels 6 rest on the upturned edges of the tray 7, and are held in place and protected by alumin-ium capping 8 which clips into a narrow channel 9 along the uppermost edge of the inverted T-shape and has downwardly-extending legs 8a which bear against the upper surface of the marginal portions 5a of the insulating panels 5. The legs 8a can be provided with resilient sealing strips along them, both to limit in-gress of water and to contact the panels to hold them in place more securely.

Figure 3 shows a timber hip rafter 10 with the insulating panels 5 resting on the angled upper surfaces thereof, held in place by a capping strip 2 pinned in place as in Figure 1.

Figure 4 shows a portion of a conservatory adapted in accordance with the invention. A conservatory will typically include a brick or timber base, win-dows 20 mounted thereon, and a roof structure consisting of rafters connecting to a wall of a house or to a hip rafter extending from a corner of the building di-agonally to the wall of the house. A rainwater gutter 21 extends along the lower Is edge of the roof. The transparent or translucent glazing panels which normally form the roof, typically of double-walled plastics or glass double-glazing units, are replaced with insulating panels 5 resting on the rafters and hip rafters as hereinbefore explained with reference to Figures 1 to 3, and held in place with capping 8, the ends of which are provided with covers for the sake of cleanli-ness and better appearance. The spaces beneath the capping may be filled with insulating material, for example shaped plastics foam.

To improve the appearance of the roof, the insulating panels 5 may be provided with the appearance of tiles or slates, by first pressing the aluminium sheet which is to form the upper skin in a shaped die to provide the tile or slate shapes, and then finishing the panel with a suitable textured paint or other finish to simulate more closely the appearance of conventional tiles or slates. Since the method of fixing leaves gaps between the panels, infill flat metal sheets con-figured to give the correct tile or slate appearance are attached to the rafters between the sheets. These may be simply glued direct to the capping on the rafters or provided with members underneath to permit the attachment while bringing the upper surface level with the uppermost surfaces of the adjacent panels 5. The spaces beneath the infill sheets and between the adjacent pan- els, i.e. over and around the rafters, may be filled with insulation material to en-sure continuity of thermal insulation across the roof.

The lowermost edge of each insulating panel 5 is preferably also of the reduced thickness, to facilitate discharge of rainwater into the gutter 21, and the transition between that portion and the remainder of the panel may be at an oblique angle to assist in directing the flow of water down the panel and into the gutter.

It will be appreciated that, while the insulating panels are most suitably formed from aluminium sheet, other materials could be employed, such as plas-tics, suitably treated to be fire-resistant, and the insulating material within can be any lightweight material with low thermal conductivity, although again treated to ensure fire-resistance. The use of stepped insulating panels enables existing buildings, such as conservatories, to be readily adapted to extend their usability, while new buildings can be constructed using existing structural elements, with-Is out the need to redesign to accommodate thicker materials. This can result in significant cost savings.

In order to provide additional light in the building, one or more insulating panels may be omitted, and high-insulating value double-glazed windows in-stalled instead.

Figures 5, 6 and 7 illustrate another embodiment wherein an insulating panel is of uniform cross-section and fitted into a profiled mounting frame 22 closely conforming to the circumferential shape of the insulating panel 5. Pref-erably, the mounting frame 22 will be constructed from a lightweight material such as aluminium or rigid plastic. The frame will preferably be a two piece con-struction whereby a top piece 23 is received by a bottom piece 24 but it will be appreciated that any other appropriate profile form could be used. The frame edges which are to be received by the pre-existing rafters 25,26,27, will be con-structed with a marginal portion 28 of the same thickness as the glazing panels to be replaced. This marginal portion will preferably extend for the entire length of the frame 22 on the sides to be received by the rafters and may form an inte-gral part of the frame profile. It will be appreciated that said marginal portion could be a separate component to the profiled frame.

Claims

CLAIMS1. A method of lowering the thermal conductivity of a building roof of the type comprising at least one spaced pair of rafters receiving between them at least one glazing panel of pre-determined thickness, and at least one retain-ing member co-operating with the rafters to hold the longitudinal edge of each of said glazing panels on said rafters, the method comprising: removing the or each retaining member from an existing building roof; removing the or each glazing panel from an existing building roof and replacing said glazing panel or panels with at least one insulating panel of sig-nificantly greater thickness than said pre-determined thickness, having upper and lower skins and thermally insulating material therebetween, said insulating panel having an edge portion of said pre-determined thickness, wherein the lower face of said edge portion sits on the upper face of said rafters and the up-per face of said edge portion is engaged by said retaining members; Is re-fitting said retaining members to engage said edge portions to retain said insulating panels on said rafters.
2. A method of lowering the thermal conductivity of a building roof according to Claim 1, wherein said edge portion is provided on a circumferential frame in which said insulating panel is mounted.
3. A method of lowering the thermal conductivity of a building roof according to Claim 1, wherein said edge portion is integrally formed with said insulating panel.
4. A method of lowering the thermal conductivity of a building roof according to any preceding claim, wherein the upper and lower skins of the or each insulating panel are fabricated from aluminium sheet.
5. A method of lowering the thermal conductivity of a building roof according to any preceding claim, wherein the thermally insulating material is expanded polyurethane.
6. A method of lowering the thermal conductivity of a building roof according to any preceding claim, wherein the thickness of the or each insulat-ing panel is at least twice the thickness of the glazing panels they replace.
7. A method of lowering the thermal conductivity of a building roof according to Claim 2, wherein the mounting frame is constructed from alumini-um.