The present invention relates to a space heating method and system for use in heating a space in a building.
According to a first aspect, the present invention provides a method of space heating for a building, the method comprising drawing at a predetermined rate air from a region adjacent the roof of the building and directing the drawn air to a space in the interior of the building to be heated.
It has been found that a "boundary" layer of air on the exterior of a building adjacent the roof of the building is of an elevated temperature compared to the "ambient" external temperature. It is believed this is as a result of the roof (which is typically covered with dark tiles) acting as an absorber of solar radiation. As the roof heats up due to absorbtion of solar energy, so the external "boundary" layer of air immediately adjacent the roof heats up. By drawing the air from the external "boundary" layer into the building a desired space can be heated. Furthermore, the layer of air on the interior of the building immediately adjacent the roof is also heated in this way, and air drawn from this layer can also be directed to a desired space in the building for heating.
Advantageously, at least some of the air used for space heating is external air drawn into the building from the "boundary" layer adjacent the exterior of the roof.
Desirably, the rate at which the air is drawn into the building is controllable and variable. This is important to ensure that the "boundary" layer of heated external air is replenished by sufficiently heated air before being drawn into the building. This is of course dependent on the quantity of solar radiation impinging on the roof and external ambient climatic conditions at any given time and also the rate at which air is drawn into the building.
Desirably the air is drawn into the building by means of suction means such as a suitable fan or other vacuum apparatus. For reasons identified above it is preferred that the
suction rate of the suction means is controllable. Preferably control means is provided to automatically adjust the suction rate of the fan or vacuum apparatus. Desirably, the control means acts in response to a signal from temperature sensor means arranged to sense the temperature of the external air layer adjacent the roof and/or the temperature of the space to be heated.
It is preferred that air is drawn into the interior of the building directly through the roof, preferably via air flow passage means defined in or by tiles positioned on the roof. Advantageously, after passing through the roof, the air is directed by ducting means to the space to be heated.
Desirably air is drawn into the building through the roof over a substantial area of the roof, preferably comprising at least 25% of the area.
The ducting means may comprise pre-formed ducts or guide channels which may be incorporated into the roof structure on the inside of the roof space, typically intermediate roof timbers supporting the roof. Alternatively, the ducting means may be partly defined by the roof structure itself and may comprise a membrane or sheet fixed internally adjacent the roof and extending across parallelly extending roof support timbers.
In certain embodiments a filter means may be positioned in the interior of the building upstream or downstream of the suction means. This may be used to remove airborne materials such as pollutant particles, pollen etc, or to reduce 03 to 02. Such filter means may comprise, for example, a filter membrane or sheet secured adjacent the interior of the roof. A further benefit of the invention is that a regular circulation of fresh "drawn" air throughout the building is ensured which provides advantages in terms of de umidification of air within the building.
In certain other embodiments, heater means may be provided to heat the drawn air. The heater means may be used to augment the heating effect of drawing the air from the region adjacent the roof.
According to a second aspect, the invention therefore comprises a space heating system comprising suction means
arranged to draw air from a region adjacent the roof of the building and ducting means along which said air is to be drawn, the ducting means being configured to direct the air to the space to be heated.
The invention will now be further described in specific embodiments by way of example only, and with reference to the accompanying drawings, in which:
Figure 1 is a schematic sectional view of a roof of a building provided with space heating means according to the invention; and
Figures 2 and 3 are schematic sectional views along A-A in Figure 1 of alternative embodiments of ducting means which may be employed in the space heating means of Figure 1.
Referring to the drawings, and initially to Figure 1, there is shown a roof 1 of a building which comprises a conventional sub-frame of rafters 2 and cross joists 3. Roof tiles 4 are fixed in a standard manner (by means of battens, not shown) to cover substantially the entire area of the roof. The tiles 4 are configured such that when in position covering the roof, air flow passages (not shown) are defined between overlapping tiles permitting air to pass through the tiled cover surface of the roof. To facilitate this the bottom edge of the tiles 4 may be provided with formations such as protrusions or alternatively recesses or flutes which define air flow passages when the lower edge of a tile abuts the upper edge of a respective underlying tile.
A suction fan 5 is positioned within the interior of the roof space and arranged to draw air at a predetermined rate through the tiled surface of the roof along suction ducts 6 which are positioned adjacent the interior surface of the roof and lead to fan 5. Ducts 6 are formed from plastics sheet membranes 7 which are secured across and below respective rows of rafters 2 and cross joists 3. In this manner an existing roof space may conveniently be modified to perform according to the invention, the air being drawn into an effectively sealed roof apex volume 15 from where it is drawn into fan 5.
The air drawn into fan 5 is directed downstream along distribution ducts 8,9 which extend to desired outlets 10 in the building through which air is introduced into the space to be heated.
For the effective performance of the invention, it is important that the rate at which air is drawn in through the roof space is such that the "boundary" layer of air (below dashed line
12 in Figure 1) is replenished due to sufficient length of contact with (and therefore warming by) the roof tiles 4. The heating system is therefore controlled using temperature sensors (not shown) the output of which is used to determine control of fan 5.
Referring to Figure 3 there is shown an alternative embodiment of ducting 6a comprising a membrane 7 positioned intermediately between the rafters 2 and standard felt underlay/batten layer 13 which support tiles 4. Spacer bars 14 are provided to space membrane 7 away from underlay/batten layer
13 to define the ducts 6a.
As a further alternative, preformed trays (not shown) may be used as ducts, and may be incorporated into the roof structure during construction of the building.