GB2125081A

GB2125081A - Thermal insulation of buildings

Info

Publication number: GB2125081A
Application number: GB08221505A
Authority: GB
Inventors: Francis Xavier Kay
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-07-26
Filing date: 1982-07-26
Publication date: 1984-02-29

Abstract

A thermal reflector unit is positioned in spaced relation to the surface of a building component (17) to reflect back thereto thermal energy emitted thereby. Also disclosed is a thermal reflector unit comprising a dished sheet (10) of, e.g., PVC or polystyrene and preferably having a lateral flange (12) for fixing it in position, at least one surface of which is reflective of thermal energy, for instance by being "silvered". The dimensions of the unit are preferably related to standard ceiling/floor joist or rafter separations to facilitate its fixing thereon to span the gap therebetween. <IMAGE>

Description

SPECIFICATION Thermal insulation of buildings This invention concerns the thermal insulation of buildings.

It is well understood that significant heat loss from the average building occurs by heat flow upwards through floors and ceilings into the roof space, and to combat this it is well known to provide insulation of various forms on the upper (cold) face of ceiling structures. The most common forms of insulation used for this purpose are glass fibre matting, laid direction on the ceiling structure surface between ceilingsupporting joists or laid across such joists, and various granular materials covering the upper surface of the ceiling, typically as an infill between joists.

The materials conventionally used for such thermal insulation are in themselves relatively poor conductors of heat but act mainly by entrapping air in their interstices and utilising the low thermal conductivity of the entrapped air as a thermal barrier. However, because the materials in question entrap air in this way they exhibit two practical disadvantages: they tend to restrict ventilation and they tend to retain moisture.

Restriction of ventilation, while useful in preventing thermal loss by convection and by extraneous draughts, is disadvantageous in that it is conducive to timber decay and can thus be detrimental to ceiling joists and adjacent timber, for instance roof timbers or timber flooring.

Retention of moisture can compound any tendency to timber joist deterioration by reason of lack of ventilation. It will be appreciated that in many installations of such insulating materials in the roof space of a building, snow and water penetration of the roof space in winter can result in substantial wetting of the insulation material and the retention of the absorbed water for long periods, especially in those regions of the material where ventilation that would assist dehydration is restricted, as in the proximity of joists and like timber in contact with the insulating material.

Moreover when these insulating materials become wet, water displace the usually entrapped air, so destroying the effective thermal barrier by replacing the relatively poorly conducting air with more thermally conductive water, and thereby reducing the insulating effectiveness of the material.

One object of the present invention is to provide a method of effecting thermal insulation of ceilings and like structures in buildings, that avoids the disadvantages of the present insulation techniques as above discussed and that is economic and simple to put into practice. A further object of the invention is to provide thermal insulation units suitable for carrying out the method of the invention.

In one aspect, the invention provides a method of effecting thermal insulation of a building component, such as a ceiling, by positioning in spaced relation to the surface of said component a thermal reflector unit adapted to reflect towards that surface thermal energy emitted thereby.

The thermal reflector unit may be formed of any suitable material but is conveniently formed of a low cost plastics material such as PVC or polystyrene. The unit is preferably disposed in closely spaced relationship to the building component surface to be insulated so as to restrict the flow of air in the gap to that consistent with adequate ventilation while avoiding excessive loss of heat by direct chilling of the surface in question.

A suitable separation between the unit and the surface is of the order of 10-1 5 mm but a large gap, such as 25-50 mm, may be tolerated and adopted for concenience, especially is precautions are taken to minimise air flow through this larger gap, as by partly closing the gap at the periphery of the unit.

The thermal reflector unit may be positioned with respect to the building component surface in any convenient manner. For the typical case of insulating a ceiling supported by timber or like joists, the thermal reflector unit may be suspended by the joists. A large reflector unit may simple span two or more joists but it is preferred, in order to achieve the desired gap dimension, to suspend suitably sized reflector units between pairs of joists, the reflector units being for instance flanged to provide for mounting on and/or fixation to the joists. Fixation may be by mechanical fastenings such as staples or by adhesive, such as by the use of double-sided pressure-sensitive adhesive strip.

The reflector units may be of any suitable configuration appropriate to its intended installation. A preferred configuration is dish-like as this facilitates suspension of fixation of the unit and also provides stiffness, and additionally assists in restricting airflow between such a unit, and especially a number of such units, and an adjacent building component surface, by providing, in effect an orifice or a number of orifices in the path of such airflow.

While the method of the invention is especially applicable to the insulation of floors and ceilings it is also applicable to the insulation of roofs and the like, either to restrict inflow of heat into a building via its roof structure or to restrict escape of heat from the roof space through the roof structure.

In another aspect the invention provides a thermal reflector unit comprising a dished sheet thermally reflective on at least one surface and adapted for fixation in spaced apart relation to a building component surface.

Such a reflector unit may conveniently be made of sheet PVC, for instance vacuum formed, the dish shape of the unit both providing stiffness enabling a relatively large unit to be constructed from thin sheet material and also facilitating fixation of the unit in relation to a building component surface. For this purpose, preferably the dish shape includes lateral flanges to facilitate suspension of the unit between a pair of joists or the like on which the unit flanges may rest.

However it should be understood that an unflanged unit may be fixed in a required position between joists by mechanical fastening, e.g.

stapling, or by suitable adhesive securing the dish walls to adjacent joists; or by inverting the dish and resting it directly on the building component surface.

The required thermal reflectivity of the unit may be inherent in the material and surface finish of the unit. For instance, the unit may be formed from white material with a suitably smooth surface on at least the side required to exhibit reflectivity. Alternatively, the required reflectivity may be provided by surface coating, for instance, by white or silver colouration applied by painting or like techniques or by foil lamination.

While PVC has the merit of being readily available in sheet form and is an ideal low cost raw material for forming the thermal reflector units of the invention, other materials may also be used td achieve performance advantages. For instance, whereas the units of the invention perform primarily as reflectors they inevitably absorb a proportion of the incident thermal radiation and additionally become heated by transference from convection currents in the gap between the unit and the adjacent building component surface. There is thus inevitably some heat loss by transmission through the unit.

Polystyrene has a thermal conductivity about 30% less than PVC and it could therefore be used to form thermal reflector units, in accordance with the invention, having improved thermal barrier properties as compared with units formed from PVC. Yet further performance improvement can be obtained by forming the units from expanded polystyrene such as is commonly used for manufacture of ceiling tiles and the like.

While thermal reflector units in accordance with the invention may be formed in sizes and configuration specifically adapted for a particular installation, ceiling insulation in many circumstances may conveniently be accomplished with the use of standard size units have a basically rectangular plan form and dimensions corresponding with the most commonly found ceiling joist dimensions and separations.

In the accompanying drawings: Figure 1 is a schematic perspective view of a thermal reflector unit in accordance with the invention and intended primarily for ceiling insulation by suspension on ceiling supporting joists as diagrammatically illustrated; Figure 2 is a diagrammatic sectional illustration of a typical installation of units of the configuration shown in Figure 1, for ceiling insulation; Figure 3 illustrates schematically the use of the unit of Figure 1 for roof insulation; Figure 4 illustrates schematically the use of the unit of Figure 1 for floor insulation; and Figure 5 is a graphical representation of the results of accelerated thermal transmission tests.

Figure 1 illustrates a convenient standard thermal reflector unit in accordance with the invention for use in insulating ceilings constructed in the common manner by the attachment of ceiling boards or panels to timber joists. Such joists commonly have a depth of 100 mm (4 inches) and a width of 38-55 mm (1 21 2 inches) arranged parallel with one another and with their adjacent flanks spaced apart at distances of 355,405 or 470 mm (14, 16 or 182 inches), as indicated schematically in Figure 1.

As shown in Figure 1, the thermal reflector unit of the invention is basically rectangular in plan form and is formed as a dish 10 having a depth of about 50 mm (2 inches) with sloping side walls 11 merging with a continuous peripheral lateral flange 12.

The unit has an overall length of about 560 mm (22 inches) and an overall width of about 455 mm (18 inches). Along the longer sides of the unit, the peripheral flange 12 has a width of about 50 mm (2 inches) so that the inner edges of the flange along these sides, where the flange merges with the walls 11, are separated by about 355 mm (14 inches), enabling the unit to be suspended by the flange 12 on its longer sides between joists 13 of a minimum of 355 mm (14 inches) separation, and also to be suspended in the same way between joists having a separation of about 405 mm (16 inches).

The flange 12 on the shorter edges of the unit has a width of about 45 mm so that the separation between the inner edges of the flange along their sides, where the flange merges with the wall 11, is about 470 mm (182 inches) to provide for suspending the unit, on the flange, between joists separated by about 470 mm (18 > inches).

The unit illustrated in Figure 1 may be installed between ceiling joists 13 as above described and in the manner illustrated in that Figure and in Figure 2 and it may also be installed between roof rafters 14 for roof insulation in the manner shown in Figure 3 or between floor joists 1 5 in the manner shown in Figure 4. It will be noted that in the arrangement of Figure 4 the dish shape is effectively inverted in relation to the (under) surface of the floorboards 1 6 with which it cooperates to reflect back heat emitted thereby, as compared with the orientation of the unit with respect to the ceiling board 17 or roof tiles 18 of the installations illustrated in Figures 2 and 3.

The thermal reflector unit illustrated in Figure 1 may be constructed by vacuum moulding of PVC sheet or in polystyrene, preferably expanded polystyrene.

Figure 5 illustrates the results of accelerated thermal transmission tests on a thermal reflector unit of the configuration shown in Figure 1 and vacuum formed from PVC sheet material having a thickness of 0.2 mm (0.0075 inch) rendered reflective on its underside by "silvering" by spraying with aluminium paint. For the purpose of these tests, this unit was disposed to close the open top of a plywood box containing a small heater and, starting from cold (ambient) the temperature of the upper surface of the unit was recorded at intervals from switching on the heater.

Similar tests were performed with the top of the heated box closed by covering with a 100 mm (4 inch) layer of glass fibre mat, and with a similar thickness of rockwool mat, respectively.

The drawing plots the measured upper surface temperatures against time from commencement of the test, with the box cold, and it can be seen that in the case of the thermal reflector unit of the invention, (curve 2) the measured surface temperature at first rose rather rapidly but soon levelled off to approach a final temperature significantly lower, within the time scale of the experiments, than those attained rather more slowly in the case of the other two materials tested (curves 1 and 3). Moreover it is apparent that in the case of the glass fibre and rockwool materials, if the tests had been extended over a longer period substantially higher final temperatures would have been reached, because the surface temperatures of these two materials were still rising at significant rates at the conclusion of the respective test periods.

Claims

1. A method of effecting thermal insulation of a building component, such as a ceiling, by positioning in spaced relation to the surface of said component a thermal reflector unit adapted to reflect towards that surface thermal energy emitted thereby.

2. A method according to claim 1, wherein the said thermal reflector unit is disposed in closely spaced relationship to the building component surface to be insulated so as to restrict the flow of air in the gap to that consistent with adequate ventilation while avoiding excessive loss of heat by direct chilling of the surface in question.

3. A method according to claim 2, wherein the spacing between the unit and the surface is 1015 mm.

4. A method according to claim 2, wherein the spacing between the unit and the surface is 2550 mm.

5. A method according to any preceding claim, wherein the thermal reflector unit is suspended by joists or the like in closely spaced relationship to a building component surface engaged by such joists or the like.

6. A method according to claim 5, wherein the unit is suspended between pairs of joists or the like.

7. A method according to claim 6, wherein the unit is flanged and is suspended by engagement of its flanges on the joists or the like.

8. A method according to claim 5 or 6, wherein the unit is fixed to said joists or the like.

9. A method of insulating a building component surface, substantially as described with reference to the accompanying drawings.

10. A thermal reflector unit comprising a dished sheet thermally reflective on at least one surface and adapted for fixation in spaced apart relation to a building component surface.

11. A thermal reflector unit according to claim 10, made of sheet PVC.

12. A thermal reflector unit according to claim 10, made of polystyrene.

1 3. A thermal reflector unit according to claim 10, made of expanded polystyrene.

14. A thermal reflector unit according to claim 10, 11 or 12 having lateral flanges.

1 5. A thermal reflector unit according to any one of claims 10 to 14, wherein at least one surface thereof has its thermal reflectivity enhanced by applied surface coating.

1 6. A thermal reflector unit substantially as described with reference to and as shown in Figure 1 of the accompanying drawings.

1 7. Every novel feature or novel combination of features disclosed herein.