GB2228078A

GB2228078A - Solar heated cavity wall for preheating ventilation air

Info

Publication number: GB2228078A
Application number: GB8902728A
Authority: GB
Inventors: Roy Wormald; Mary Elizabeth Sweeney
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-02-08
Filing date: 1989-02-08
Publication date: 1990-08-15
Also published as: GB8902728D0

Abstract

A new or an old conventional cavity wall has a selective coating (2) applied to its external surface to produce high solar absorptivity but low longwave emissivity. Glazing (1) spaced from the outer wall (3) reduces heat losses. Heat produced by the absorption of solar radiation on the selectively coated surface, passes by conduction through the outer wall into the cavity. External air flowing through ducts below the glazing to the bottom of the cavity (7) is heated and exits at the top of the cavity into an internal room (9). A small fan (8) may be inserted into the air stream. <IMAGE>

Description

SOLAR HEATED CAVITY WALL FOR PREHEATING VENTILATION AIR This invention relates to a solar heated cavity wall for the preheating of air used in ventilation. Cavity walls are a standard form of construction in the building industry, and consist of two leaves of a building material (such as brick, block or concrete), with a cavity in between. The leaves are often of lOOmm thickness, the cavity has in the past been usually 50mm in width.

On sunny days the outer leaf of such a wall will be warmed by the sun, and conduct heat to the building interior. The efficiency of such heat transfer is however, reduced by large heat losses from the unprotected external face.

Special solar heat storage walls have been built, which utilise a massive outer leaf, painted matt black, to store incident solar radiation. The outer surface has been covered by glazing to reduce the connective and radiative heat losses, and the stored heat is allowed to enter the building. Special selective coatings of low emissivity for lor.g wave radiation and high absorptivity for short wave radiation have been used to increase the performance of these walls.

According to the present invention these features are applied to a conventional cavity wall, either newly built or as a retrofit to an existing c. To the external surface of this wall, a selective coating, a framework, and glazing is applied. A suitable air gap separates the glazing from this wall. Heat is conducted through the outer leaf into the cavity and fresh air drawn into the cavity from the extericr is heated and exits at the top of the cavity into the building. A stall fan may be installed into the air stream to improve the solar wall's performance.

A specific embodiment of the invention will now be described by way of example, and reference is made to the accTpanying drawing in which Fig. 1 shows a section of a wa'l Fig. 2 shows a wall in perspective from the front Fig. 3 shows a wal' in perspective from the back The external leaf of this wall (3) is built of 102.5mum brick, and faces south. It has a selectively coated foil () adhering to its front surface, and an air gap of lOOmm between that surface and the single glazing of normal glass in a suitable sealed framework (1).

Heat from the absorption of solar radiation passed through the wall by conduction and enters the cavity (4). This is of 5Omv. thickness and the rear leaf of the wall is built of lOOnr. aerated concrete blocks (6). 25mar thickness of an ins-lating material such as fibreglass or polystyre..e foam (5) is fixed to the cavity side of the blocks. Air enters the cavity via small ducts (7) running from a position below the glazing, through th external leaf of the wall. The air is heated and rises in the cavity to exit through a duct in the inner leaf, at the top of the wall (9). The performance of the wall is improved if a small fan is placed in the exit duct to facilitate ventilation.

Claims

1. A solar heated cavity wall for preheating ventilation air built from standard construction materials, with a selective coating material applied to the front surface of the outer leaf. Such a cavity wall has a thin outer leaf of a building material, the outer surface of which is provided with a window frame and glazing and the surface itself covered by the selective coating. Solar radiation transmitted through the glazing heats the outer surface of the cavity wall, this heat passing solely by conduction through the outer leaf into the cavity. Ducts are provided in the top of the inner leaf and in the bottom of the outer leaf, to enable fresh air to flow from the external environment directly into the bottom of the internal cavity where after heating it enters the interior from the top of the cavity.

2. A solar heated cavity wall for preheating ventilation air, as in claim 1, where a small fan is inserted into the steam of flowing air to improve the performance of the solar wall.