It is known to provide a dwelling with a ventilation system which comprises a fan disposed in the loft or roof space of the building and arranged to discharge air into the living or accommodation space of the building. This places the accommodation space under a slight positive pressure, which forces air to flow out of the building through gaps in windows, doors etc. The effect is that the accommodation space is subjected continuously to a ventilating flow of air, which acts to remove or prevent the build up of condensation and also to remove or prevent the possible build up of radon gas. Such ventilating systems are often installed in dwellings to overcome the tendency in some buildings for damp conditions to develop or possibly radon gas to accumulate.

Our International patent application WO 00/11410 discloses a ventilating system which is arranged to draw in air from selected different locations, according to whether it is desired to deliver warm or cool air into the accommodation space of the building.

We have now devised an improved ventilation system, which utilises available warm air to heat water for the building.

In accordance with the present invention, there is provided a ventilation system for a building, comprising fan means arranged to draw in air from selected locations exterior of the accommodation space of the building and deliver said air into said accommodation space, means for heating air from solar radiation, and means for passing the solar-heated air through a heat exchanger to heat water for the building.

This ventilation system is able to deliver air into the accommodation space of the building and assist in either warming or cooling the accommodation space, depending upon the location from which the air is drawn in. When there is

sufficient solar radiation, the solar-heated air may be passed through the heat exchanger to heat water for the hot water supply of the building. When the solar radiation is insufficient for this purpose, it may still be sufficient to warm air, drawn into the system from one or more of the inlet locations and passed through the solar air-heating means, before this warmed air is delivered into the accommodation space.

The system is preferably arranged so that it can return, to the solar air-heating means, the air passed through the heat exchanger, in a closed-circuit circulation path.

Preferably, however, the system comprises control means operable, under predetermined conditions, to pass at least some of the air, drawn in from the selected locations, through the heat exchanger (preferably via the solar air-heating means), before it is delivered into the accommodation space.

Preferably the solar air-heating means comprises an enclosure, preferably in the form of one or more generally planar panels, for positioning on the exterior surface of the roof of the building.

Preferably the ventilation system is arranged to draw in air, selectively, either from within the loft or roof space of the building, or from a location exterior of the building, for example under the eaves. The ventilation system may be arranged to draw in air from both such locations simultaneously, under predetermined conditions.

The control means of the ventilation system is preferably arranged to monitor the temperature of the air available at the respective inlet locations, and determine from which location or locations to draw in air, according to the temperature desired in, or to be delivered to, the accommodation space. Preferably a selector is provided in the accommodation space, to set the desired temperature, and the control means is arranged to monitor the actual temperature in the accommodation space and the temperature of the air being

delivered into the accommodation space, to determine whether warm or cool air is required to be drawn in, which available location or locations to draw it from, and at what rate of flow.

The control means is also arranged to monitor the temperature of the air available from the solar air-heating means, and determine when to circulate this air through the heat exchanger and when to pass air from the available inlet locations through the heat exchanger.

Preferably the ventilation system comprises a first fan for drawing in air from the selected exterior locations, and a second fan for causing air to flow through the heat exchanger from the solar air-heating means.

The system may be arranged to maintain a positive air pressure within the building. It may be arranged to recirculate a proportion of air from within the building, possibly so that the air pressure within the building is neutral: in this case a further heat exchanger may be provided to exchange heat between the air being delivered into the accommodation space and the air being extracted therefrom.

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawing, the single Figure of which is a schematic diagram of a ventilating system in accordance with the present invention, installed in the loft of a dwelling.

Referring to the drawing, there is shown the apex roof 10 of a house or other building, the apex roof providing a loft or roof space 11 above the ceiling 12 to the accommodation space 13 of the building: typically the accommodation space comprises a number of individual rooms. Further, the building is equipped with a hot water system, for supplying hot water to a number of hot water outlets such as the taps of a kitchen sink, a bath or wash basin and/or a shower.

A ventilating unit 14 in accordance with the present invention is disposed in the roof space 11 of the building and

has a number of ducts 15,16, 17,18 and 19 coupled to it. The ventilating unit 14, in the example shown, comprises two air handling units 20,30 each comprising an enclosure formed on one side with a single port (P1 and P2, respectively) and on its opposite side with three ports (P3, P4, P5 and P6, P7, P8 respectively). The ports P3 and P6 of the respective air handling units are coupled to a common manifold M1, to which the duct 17 is also coupled, via a heat exchange 22. The ports P4 and P7 of the respective air handling units are coupled to a common manifold M2, to which the inlet duct 15 is also coupled. The ports P5 and P8 of the respective air handling units are coupled to a common manifold M3, to which the inlet duct 16 is also coupled.

The ports Pl, P2 of the respective air handling units are provided with fans F1, F2, each fan having an air filter (not shown). The ports P3 to P8 of the air handling units are each provided with an electrically controlled damper D, for opening or closing the respective port.

The port P1 of the air handling unit 20 has the duct 18 coupled to'it, this duct being coupled at its other end to one or more diffusers 18a on the ceiling 12 of the accommodation space 13 of the building, in order to deliver a flow of air into the accommodation space, with the effect of maintaining a positive air pressure within the building. The fan F1 serves to deliver the air through the duct 18, the air being drawn into the ventilating unit 14 through inlet duct 15 and/or through inlet duct 16, as will be described below.

A solar air-heating unit, comprising a generally planar enclosure 24, is mounted on the exterior roof surface, preferably on the most southerly-facing side of the building.

The outlet duct 19 of the ventilating unit is coupled at one end to the port P2 of the air handling unit 30, and at its other end to the solar air-heating enclosure 24 adjacent its lower end: the duct 17 is coupled at one end to the enclosure 24 adjacent its upper end and, at its other end, to the heat

exchanger 22. The heat exchanger 22 is arranged for heating water for the hot water supply system of the building. The fan F2 of the air handling unit 30 is arranged for circulating air through the solar air-heating enclosure 24, then through the heat exchanger 22 and either back to the air handling unit 30 or to the air handling unit 20.

The ventilating unit 14 further comprises a controller (not shown) which serves to monitor the temperature of the air available at the inlets to the ducts 15,16 and 17, the air temperature in the accommodation space 13 of the building, the temperature of air being delivered into the accommodation space, and a desired temperature set by a manual selector provided in the accommodation space. The controller then determines whether to draw inlet air from within the roof space (via inlet duct 15), or from outside the building (via inlet duct 16), or a mixture of air from both locations: the controller then controls the dampers D of the ports P3-P8 accordingly.

In general, the ventilating unit serves to deliver warm air into the accommodation space, during periods of cold or cool ambient conditions. For example in winter, the unit will serve to draw in warm air from the roof space, through inlet duct 15, the fan F1 then delivering this air into the accommodation space through the outlet duct 18: it will be noted that the air in the roof space is replenished by air entering under the eaves (as indicated at A), this air becoming warmed by solar energy and by heat rising from the accommodation space and into the roof space. On a sunny winter's day, the controller will find that the air within the solar air-heating enclosure 24 is warmed by solar radiation: in this case, the air drawn into the manifold M2 from inlet duct 15 is circulated, by the fan F2, through the enclosure 24 and back into the air handling unit 20, before being delivered into the accommodation space via duct 18. Even on a sunny day, the air from the solar air-heating enclosure may not be warm

enough to heat water in the heat exchanger 22, so no water is passed through the heat exchanger under these conditions.

In spring or autumn, for example, the controller may act so that the ventilation unit draws in air through the inlet duct 15 and delivers this into the accommodation space, and at the same time circulates heated air, from the solar air-heating enclosure 24, through the heat exchanger 22, the air handling unit 30 and back through duct 19 to the enclosure 24. In this way, warm air is delivered into the accommodation space, whilst solar-heated air is used to heat water for the hot water supply of the building.

The air delivered into the accommodation space may be drawn in through both the duct 15 and the duct 16 (which draws air in from under the eaves of the building). For example, warm air from within the roof space is then mixed with cool air from under the eaves, to achieve an intermediate temperature for the air delivered into the accommodation space. At other times, for example in the summer during the day, cool air may be drawn in from under the eaves only (i. e. through duct 16 only), for delivery into the accommodation space: simultaneously, air heated in the solar air-heating enclosure 24 may be circulated through the heat exchange 22, as described above, to the heat water for the hot water supply.

At night in the summer, cool air from under the eaves (and drawn in through duct 16) may be passed through the air handling unit 30, the solar air-heating enclosure 24, the heat exchanger 22, and the air handling unit 20, for delivery through duct 18 into the accommodation space. Whilst in the enclosure 24, the air loses heat to the atmosphere, so that the cool air drawn in from under the eaves is further cooled before delivery into the accommodation space.

It will be appreciated that the ventilating system which has been described delivers air into the accommodation space, either to help warm the accommodation space or to help cool it, according to the requirement which varies from time-

to-time. The solar air-heating enclosure is used either to further warm (or cool) the available air before delivery into the accommodation space, or to heat water (in the heat exchanger 22) for use in the hot water supply.

As previously mentioned, the ventilating system may include a fan for extracting air from within the accommodation space and for expelling this air to the exterior of the building via a further heat exchanger which serves to exchange heat between the air being expelled from the accommodation space and the air being delivered into it.