GB2338727A

GB2338727A - Eaves ventilator with directional baffles

Info

Publication number: GB2338727A
Application number: GB9813707A
Authority: GB
Inventors: Paul Bramhall; David Luke
Original assignee: B & S Components Ltd
Current assignee: B & S Components Ltd
Priority date: 1998-06-26
Filing date: 1998-06-26
Publication date: 1999-12-29
Also published as: GB9813707D0; GB2338727A8

Abstract

An eaves ventilator 2 which fits between rafters 9 in a roof space which has directional baffles 3 and 6 which will maintain the integrity of the ventilation path 5 by compressing the ceiling insulation 4 in both the lower and upper edges.

Description

1 2338727 EAVES VENTILATOR WITH DIRECTIONAL BAFFLES Eaves ventilators are

a well known component of roof structures, they are also known as rafter trays. They are fixed between rafters at the eaves of roofs to allow cross ventilation from one side of the roof to the other. These are necessary to avoid condensation forming in the roof void of domestic dwellings. Condensation in the roof can cause the roof timber to rot or metal fixings to corrode.

Roof ventilation is a building regulation BS 5268 part 3 1985 Section 3/8.1 and 8.3. It is also a requirement of the N H B C.

Eaves ventilators are manufactured by various companies and are usually of a vacuum pre-formed plastic or a thin metal construction. They are a simple tray configuration with fixing lugs which are stapled or nailed to the top edge of the rafter. They are available in widths to suit rafter centres of 40Omm, 450mm and 60Omm. The ventilation path formed by the tray is parallel with the top of the rafter and this dimension is generally 300 - 350mm. going up the rafter. This parallel ventilation path is prone to being blocked by the insulation material either at the lower edge or upper edge of the eaves ventilator. This has become a serious problem since insulation standards have increased the required thickness of insulation material up to 150mm thickness minimum and increasingly spec ied by architects and housing associations where they require 20Omm thickness of ceiling insulation.

It is important to fully insulate over and around the wallplate so that the ceiling insulation is continuous and butts the cavity insulation otherwise a cold bridge will be formed - as referred to in the Building Research Establishment report'llermal Insulations Avoiding Risks, 1994 2. 1 (a)'. This is a particularly vulnerable area of the roof structure because 0.

2 this is where the warm moist air rising in the habitable room below meets the coldest part of the roof where the ventilation path is formed into the roof void. It is also important to form a ventilation path over the whole of the ceiling insulation to a mininurn of 25mm contffluous gap irrespective of roof pitch as referred to in the Building Research Establishment Report 1994 2. 1 (c).

Eaves trays are prone to being blocked by the ceiling misulation when pushed in too far. As it passes the lower edge of the rafter tray it win expand to its fiffl thickness and win block the ventilation path. The ceiling insulation can also block the ventilation path at the upper edge of the eaves tray by the expansion of the ceiling insulation to its full depth after installation. The causes of these problems are inaccurate positioning of the eaves trays and or poor fitting in difficult confmed spaces. After the roof is covered it is difficult for building inspectors to cheek that this important operation is carried out correctly. It can cause considerable heat loss and deterioration of the decoration to the ceilm"g and wall junction.

3 According to the present invention there is provided an caves ventilator with directional baffles. The caves ventilator is a tray section with upstands to form a 25mm - 50mm air path and fixing lugs which are fixed to the top edge of the rafter by staples or nailing. The ventilation path is parallel to the rafter and by incorporating angled baffles at the lower edge and at the upper edge of the eaves ventilator this will direct the insulation material away from the ventilation path towards vertical direction at the lower edge of the eaves ventilator and towards a horizontal direction at the upper edge. This will prevent the possibility of blockage by the insulation material when installed at either the lower edge or upper edge.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 shows in perspective the eaves ventilator with baffles; Figure 2 shows a section through the eaves of a roof with the caves ventilator with baffles in position; Figure 3 shows a section through the eaves of a roof with the eaves ventilator with baffles in position and the ceiling insulation in place.

Referring to the drawing the caves ventilator 2 has a baffle 3 at the upper edge of the eaves ventilator 2 which will direct the ceiling insulation 4 downwards towards the horizontal plane to avoid blockage of the ventilation path 5 at the upper edge of the eaves ventilator 2. There is also a baffle 6 at the lower edge of the eaves ventilator 2 which will direct the ceiling insulation 4 downwards towards the vertical plane so that it butts the cavity insulation 7. The eves ventilator 2 has fixing lugs 8 which are stapled to the rafters 9.

Claims

1. In a building a pre-shaped caves ventilator made from plastic or thin metal which, when fixed between the rafters at the eaves, forms a ventilation gap of between 25mm to 50mm between the ceiling insulation material and the roofing felt and at the upper edge has a baffle formed at an angle towards the horizontal plane from the angle of the rafter to cause a directional trajectory of the ceiling insulation away from the ventilation path to the roof void.

2. In a building a preshaped eaves ventilator, as claimed in claim 1, which has at the lower edge a baffle formed at an angle towards the vertical plane from the angle of the rafter to cause a directional trajectory of the ceiling insulation away from the ventilation path to the roof void and downwards to butt or lap the cavity insulation.

3. In a building a pre-shaped eaves ventilator, as claimed in claim 1 and claim 2, which has a baffle at the upper edge as claimed in claim 1, and has a baffle at the lower edge as claimed in claim 2.