GB2138050A

GB2138050A - Ridge-capping with ventilation

Info

Publication number: GB2138050A
Application number: GB08409840A
Authority: GB
Inventors: Francois Blanc
Original assignee: Societe des Mines et Fonderies de Zinc de la Vieille Montagne SA
Current assignee: Societe des Mines et Fonderies de Zinc de la Vieille Montagne SA
Priority date: 1983-04-14
Filing date: 1984-04-16
Publication date: 1984-10-17
Also published as: GB2138050B; DE3414700A1; FR2544363A1; FR2544363B1; LU85297A1; NL8401199A; BE899400A

Abstract

Ridge-capping for a double sloping roof comprises an inner ridge-tile 2 of zinc of semi-tubular shape having side edges comprising retaining lugs 13 for attachment to the two slopes of the roof. The inner ridge-tile is formed with a succession of openings 6 to ensure the outlet of air from the space below the roof and has a succession of transverse outer ribs 7 formed as stampings from the body of the inner ridge-tile. An outer ridge-tile 1 of zinc of semi-tubular shape rests and is fixed to the inner ridge-tile by rivets 10 engaging the ribs 7. <IMAGE>

Description

SPECIFICATION A system of ridge-capping with continuous ventilation The present invention relates to a new system of ridge-capping with continuous ventilation intended more particularly, but no exclusively, for rooves constructed from flat elements such as slates or shingle-boards.

Generally, modern architecture increasingly prefers rooves with a slight inclination and which are made water-tight by the roofing materials used. A water-tight roof whose permeability to water vapour is low or zero, however causes certain problems. Independently of the roofing material, the water-tight roof favours the formation of condensation on the inner face of the roofing or of the infrastructure, which may cause considerable damage.

Air almost always contains water in the, form of vapour in suspension in the air, which is at a certain pressure, depending on the quantity of vapour per unit volume and temperature.

At a given temperature, the pressure of the water vapour cannot exceed a certain limit, the saturation pressure. In this case, the air is saturated with water, the relative humidity is thus 100%. Owing to the fact that the saturation pressure increases when the temperature rises, hot air may contain more water than cold air. If the hot and saturated air is cooled, part of the water vapour must thus be eliminated, which gives rise to the formation of condensate. Like all gases, water vapour seeks conditions of equilibium. If a difference exists between a tepid and humind location and the cold stagnant air under the infrastructure of the roof, there is a diffusion of water vapour across the roof, in order to counter-balance the pressures. The diffusion of vapour takes place all the quicker the higher the pressure difference and the more permeable the material.This is also true when the relative humidity is higher in the roof than in underlying locations.

The diffusion of water vapour depends on the pressure and not the relative humidity, which no-one tended to believe.

In conclusion, if the temperature is lowered beyond the dew-point, condensation occurs.

The condensate thus forms when a roof is not constructed according to building regulations and the hot and humid air of the interior is able to move into the cold regions of the roof. The higher the humidity of the internal air and the more the temperature difference between the inner air and the outer air is accentuated then the greater the risk of formation of condensate.

As has been pointed out, the damage due to condensation is considerable, for example we can mention: -metal rooves are attacked by stagnant condensation, -damage to thermal insulation materials and reduction of the ability to withstand heat, -destruction of the roof support timbers or of the chip-board panels due to rotting, mildew or swelling.

In fact, it is the conservation of the entire infra-structure which is compromised.

The difficulties can be overcome solely by constructing according to building regulations: -either by evacuating the water vapour (ventilation) which penetrates the roof before condensation occurs (cold roof or ventilated roof), -or by insulating the roof with respect to underlying areas (blocking vapour), so that no vapour is able to penetrate (hot roof).

It is for cold or ventilated rooves, which are technically more perfect than hot rooves, that the system of ridge-capping with continuous ventilation is intended, the latter being the object of the present patent application.

However, it is important to note that the ventilated roof is not a new creation, the basic type is the traditional roof with a sloping covering (thatch, shingle-boards, tiles, slates. . .) over unihabited roof space serving as grain stores or repositories for old furniture and various objects, reputed to be sound and dry. Some times ventilation occurs through spaces which are left open between the rafters or when, even without the admittance and escape of air, irregularities and gaps between the roofing material allow a regualtion of the temperature and humidity conditions.

In all these cases, the purpose of ventilation is to eliminate water vapour which has diffused through the ceiling.

This ventilated roof is the seat of active natural ventilation with the outside air which operates all year long between the two membranes (roofing-insulation or ceiling).

In summer, the water vapour partial temperatures and pressures are roughly counter-balanced between the inside and the layer of ventilated air. There is thus no danger of condensation except in some particular cases, which are quite infrequent, with rooves consisting of light metal, at the time of a sudden change of temperature and relative humidity of the outside air (storms). However, the ventilation plays a very important role by eliminating a major part of solar radiation. The ventilation becomes an active complement to the insulation, which is essential for the comfort of the premises.

As regards the admittance to and escape of air from the ventilation space, despite the incoherences which one may find in special iszed literature, one can say generally that the section of the air outlets should be greater than the sum of the sections of the inlets, so that the air inlets and air outlets must allow the quantity of air calculated in order to ensure ventilation to pass freely.

Knowing the circulation of air necessary in m3 per hour for eliminating water vapour diffused through the total surface of the ceiling or through a section having a width of 1 metre, it is thus easy to determine the admissible inlet and outlet sections of air.

As regards the arrangement of ventilation orifices, the conventional arrangement consists of a row of orifices on the slope of the roof, another on the ridge. These orifices may be separate orifices for example (ventilation holes) not ensuring complete ventilation.

For the purpose of obtaining complete and continuous ventilation at the outlet, French Patent 77 23 957 in particular proposes a ventilation system provided by means of linear products able to fit roofing consisting of conventional flat members such as natural slates or tiles made from asbestos cement.

As the air inlet, this system uses conventional devices arranged on the slope, such as commercially available ventilation grills.

As regards the air outlet, this patent proposes a ridge-capping system with continuous ventilation comprising essentially: -two deflecting hip-sheets resting flat on the roofing and situated on either side of the ridge, -a ridge-tile located above the ridge and whereof the side edges overhang the said hipsheets, and -means for fixing the said ridge-tile and adjusting the height of the latter depending on the gradient of the slope of the roofing.

Thus, the air outlet section may be adjusted, either by modifying the spacing of the hip-sheets and/or by adjusting the height.

The invention relates more particularly to the production of ridge-capping with continuous ventilation, of a simpler construction and which is easier to use and whereof the watertightness is considerably improved, in particular as regards protection against the penetration of powdery snow.

To this end, there is provided according to the invention the ridge-capping system with continuous ventilation characterised by a double ridge-tile comprising an inner ridge-tile having a semi-tubular shape of which side edges comprise means for attachment to the two slopes of a double sloping roof, on either side of the ridge of the roof, said inner ridgetile also comprising a succession of openings intended to ensure the outlet of ventilation air and, at least in its central part, a succession of transverse outer ribs and an outer ridge-tile having a semi-tubular shape, which comes to rest on and is fixed to the inner ridge-tile in the vicinity of said ribs.

The inner and outer-ridge tiles can be of metal.

In this respect it should be noted that the afore-said transverse ribs may be integral with the inner ridge-tile and for example consist of stamped parts. They may also consist of attached members of, for example, steel initially formed separately from the inner-ridge tile and then attached thereto.

The inner and outer ridge tiles can each be of a substantially semi-cylindrical shape, and may be of zinc preferably pre-patinated, the air outlet openings may be in the top or apex of the inner-ridge tile.

One advantageous feature is that the shape of the ribs provided in the inner ridge-tile can be such that their relief is smaller in the central part than at the ends. Thus, when the outer ridge-tile is assembled on the inner ridge-tile, a position in which the two members are pressed one against the other and are connected for example by riveting in the region of the ribs, a passage is obtained between these two members whereof the section is greater at the ends than in the central part.

This arrangement provides that the particles of water or snow, which, pushed along by the wind, penetrate beneath the ridge-tile, accelerate as they progress towards the upper part, due to the reduction of the section for a constant flow; when they reach the ventilation openings, they are slightly deflected upwards by the ascending current which comes from the underface of the roofing. Given the speed of the particles at this instant, which may be increased further by the reduced pressure produced in the second part of the journey, due to the suction effect of the wind on the leeward slope of the roof, in the majority of cases, these particles will not enter the ventilation openings, but will pass through the ridge.

Another feature is that the side edges of the inner ridge-tile can be each extended, over their entire length, by at least one flat part, forming an angle of approximately 30 towards the outside with the horizontal. In order to ensure water-tightness between the roofing members and the ridge-tile, against the possible ascent of water or powdery snow under the action of the wind, this flat part may comprise at its end a strip of lead fixed by double clipping. Moreover, in order to ensure fixing of the ridge-tile to the corresponding slope of the roof, steel retaining lugs may be located, at regular intervals, below the strip of lead. These retaining clips may be provided with holes for the passage of nails or screws for attachment to the roofing.

As for the ridge-tile, it may comprise at each of its side edges, a rim which is driven back and which prevents deformation.

An embodiment of the invention will now be described hereafter, by way of example, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic perspective view with partial cut-aways of a ridge-capping system according to the invention, and Figure 2 is a cross-section of the ridgecapping system shown in Fig. 1.

The ridge-capping system illustrated in these drawings, comprises, as mentioned previously, two ridge-tiles 1,2 fitted one on the other.

The outer ridge-tile 1 is composed of a hollow half-cylinder of pre-patinated zinc, ter minated at each end and over its entire length by a rim 3 which is turned back and prevents deformations. The inner ridge-tile 2 is also composed of a hollow half-cylinder of prepatinated zinc, extended at each of its ends and over its entire length by a flat part 5, forming an angle of 30 towards the outside with the horizontal.

Cut at the centre of the development of the inner ridge-tile 2 are rectangular transverse openings 6. These openings 6 are intended to ensure the outlet of ventilation air.

At regular intervals, transverse ribs 7 are stamped towards the outside, in the central part of the inner ridge-tile 2. These ribs 7 comprise three holes 8, one at the centre and the other at approximately 60 on either side of the longitudinal median plane of symmetry.

These ribs 7 serve to support the outer ridge-tile 1 and to ensure an intermediate air passage 9.

The attachment of the two ridge-tiles 1, 2 is carried out in the vicinity of the ribs 7, for example by means of rivets 10 passing through holes 8.

As can be seen more particularly in Fig. 2, the relief of the ribs 7 is less in the central part of the inner ridge-tile 2 than at the ends and consequently the section of air passage 9 between the two ridge tiles 1,2 is less in the central part where the openings 6 are situated. One thus obtains an acceleration, during its travel, of the stream of air circulating between the inner and outer ridge-tiles.

A strip of lead 1 2 is fixed by double clipping at the ends of the outer flat parts 5 of the inner ridge-tile 2. Also disposed at regular intervals below this strip of lead 1 2 are steel lugs 1 3 each comprising two holes 14. These lugs 1 3 serve for the attachment of the ridgecapping system to the roofing 15, by means of nails 1 6 or screws passing through holes 14.

The assembly of the ridge-capping system with continuous ventilation described previously may take place as follows: First of all, the roofing 1 5 is fitted completely leaving an opening 1 7 of approximately four centimetres at the apex.

The ridge-capping system is then fitted along the axis of the roof and it is fixed by screws 1 6 by means of fixing lugs 1 3. The ridge-tiles 1, 2 fit together by overlapping.

Finally, the strip of lead 1 2 is bent over the top of the fixing lugs 1 3 then the finishing members are fitted.

It should be noted that the ridge-capping system may comprise a certain number of accessories for finishing the ends or for adapting the ridge-capping system to various features of the roofing (L-shaped sections, Tsections etc. .

Claims

1. A ridge-capping system with continuous ventilation, characterised by a double ridge-tile comprising an inner ridge-tile having a semi-tubular shape of which side edges comprise means for attachement to the two slopes of a double sloping roof, on either side of the ridge of the roof, said inner ridge-tile also comprising a succession of openings, intended to ensure the outlet of ventilation air and, at least in its central part; a succession of transverse outer ribs, and an outer ridge tile having a semi-tubular shape which rests on and is fixed to the inner ridge-tile in the vicinity of said ribs.

2. A system as claimed in claim 1, in which the inner and the outer-ridge tiles are each of substantially semi-cylindrical shape.

3. A system as claimed in claim 1 or claim 2, in which the inner and outer ridge tiles are each formed of metal.

4. A system as claimed in claim 3, in which the metal is zinc.

5. A system as claimed in claim 3 or claim 4, in which the metal is pre-patinated zinc.

6. A system as claimed in any one preceding claim, in which the said openings are disposed in the vicinity of an apex of the inner-ridge tile.

7. A system as claimed in any one preceding claim, in which the shape of each said rib provided on the inner ridge-tile is such that its relief is less in the central part of the rib than at its ends.

8. A system as claimed in any one of the preceding claims, in which the transverse ribs are formed integrally with and from the material forming the inner ridge-tile or said ribs consist of members separate from the innerridge tile and attached thereto.

9. A system as claimed in claim 8, in which the ribs are of stamped metal, and when said stamped ribs are formed integrally with and from the material of the inner-ridge tile the system is in accordance with any one of claims 3 to 5.

10. A system as claimed in any one preceding claim, in which the side edges of the inner ridge-tile are each extended, over its entire length by at least one flat part forming an angle of substantially 30 towards the outside with the horizontal.

11. A system as claimed in claim 1, in which the said flat part comprises at its end, in order to ensure its tightness on the roof, a strip of lead fixed by double clipping.

1 2. A system as claimed in claim 4 or claim 5, in which steel retaining lugs are arranged, at substantially regular intervals, below the strip of lead.

1 3. A system as claimed in claim 12, in which the said retaining lugs are provided with holes.

14. A ridge-capping system with continuous ventilation, substantially as hereinbefore described with reference to the accompanying drawings.