NZ622443A - A building configuration employing solar energy to generate a ventilation air current - Google Patents

Abstract

A wide gap is formed in the main roof or between the main roofs 4, 5 of a building such as a cattle shed or barn, and a sub-roof 6 is formed below the wide gap and at a level below that the main roof(s) to form at least one large ventilation opening 7 between the roof or roofs and the sub-roof from beneath the roofs to the wide gap. The main roof or roofs overlap the sub-roof 6 so that the weather shelter integrity of the roof is preserved. The sub-roof may be raised or lowered to vary the ventilation area 7. The top surface of the sub-roof is a low albedo surface to receive and absorb solar radiation and heat the air above the sub-roof to amplify a convection current of warm air rising off the sub-roof which in turn creates a flow of cooler air through the living spaces 1, 2 of the building from the sides of the building and through the ventilation openings 7. Partially permeable barriers 8 may be raised or lowered into the ventilation openings to control the flow of air through the ventilation openings according to ventilation requirements.

Description

NEW D PATENTS ACT 1953 IP Number: 622443 Application Date: 14 March 2014 COMPLETE SPECIFICATION A BUILDING CONFIGURATION EMPLOYING SOLAR ENERGY TO GENERATE A VENTILATION AIR CURRENT l, Ian d Marsden of 43 Studholme street, Temuka, 7920 New Zealand, a New Zealand Citizen HEREBY declare the invention for which I pray that a patent be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement:- Page 1 of 6 TECHNICAL FIELD OF THE INVENTION The invention relates to a particular uration of a building which es solar energy on its roof to enhance ventilation.

BACKGROUND TO THE INVENTION A building requires ventilation to remove hot, stale, or contaminated air, and to t excessive internal temperature rise from various heat sources. The flow of air through the building conveys away the heat and airborne contaminants, maintaining an acceptable environment for occupant humans, animals, equipment, inventory, and the like (referred to hereinafter as "occupants").

Natural (unpowered) ventilation is desirable, avoiding installing powered s such as fans because these are typically noisy, intrusive, occupy building space, consume energy, and are costly to purchase, run, and maintain.

Ventilating a building by using natural air currents, is difficult to achieve on windless days.

This is also typically a time of t need as cloud cover may not be present to shield the building from the sun. In this windless circumstance the only natural driving force to generate air movement is thermal convection, whereby hot air expands and becomes more buoyant, rising and drawing in cooler air from the ndings to replace it.

The building services, occupants, and sun shining on the roof all generate heat inside the building. If air is able to flow in at low level and exhaust at high level, l convection will promote some air movement through the building. The airflow rate depends on ature difference between interior and exterior air; the hotter the heated interior air compared to outside air, the more buoyant it is and the faster it rises and flows out through the high—level exhaust vents.

Temperature inside the building will rise until equilibrium is achieved, where the airflow constantly exhausts at a temperature and rate that is in balance with the heat being put into it. The lower the achievable airflow rate, the higher the equilibrium temperature will be—and hence, the hotter and more detrimental the interior nment.

Status-quo solutions to increase air flow, such as applied to animal barns, typically create a ”chimney effect" by configuring the building with gs in the walls at low level to let fresh air in, and with a tall, steeply—sloping roof, having ventilation openings at the top, or more commonly a single continuous ridge vent, to let hot air out. This ng is inherently bulky and expensive to build, and it also has a high proportion of wasted volume—internal space that is reserved almost ively for w. The sun heating the roof only slightly s the convection air movement, as most of the air movement generated by the hot roof is on the e surface, taking no part in the building ventilation. To minimise exhaust air flow resistance, the ng roof ridge vent might have its rain shield located on the inside of the building instead of on the outside, so that the hot air flowing out travels a straight path, rather than changing direction to pass around an external hood.

However an internal rain shield would only marginally improve ventilation performance, and requiring an extra drainage system for incoming ter, it would not provide good performance value for the extra cost. It would contribute little or nothing to reducing the roof height required to e a "chimney ".

The invention, bed in the Statement of lnvention below, makes an internal-weather— shield configuration much more effective by employing solar heat to boost performance, eliminating the need for the building to achieve a "chimney effect" to promote air flow. The roof ridge opening is made very large and the opening is shielded against inclement weather by a large internal "Sub— Page 2 of 6 Roof", that is overlapped by the main roof wings on each side. The Sub-Roof is clad with a low- albedo material to absorb solar energy and release it as heat; this heats the air above the of, causing it to rise. The rising hot air applies a suction to the ventilation exhaust openings, and thus the overall rate of building ation is increased. It is no longer necessary to have a tall, steep roof, to create a "chimney effect" for ventilation. Compared to a steep-roof—ventilated building, the new low profile configuration has improved airflow, is less visually ive, better utilises internal volume, has less shade impact on neighbours, is less vulnerable to storm winds, and costs less to construct and maintain.

Typical relatively open building types that require heat and/or fume removal, and which could benefit from this configuration include: animal accommodation barns, bus depots, sheltered car parking, show or market venues, ft hangers, and the like.

STATEMENT OF INVENTION AND ED DESCRIPTION One preferred form of the invention will now be described, referring to the drawing.

Occupants having the highest ventilation and g need typically occupy building areas 1 and 2, while area 3 occupants typically have the least need. For example, an animal barn areas 1 and 2 are ed by s, while area 3 is fenced off and used for e or machinery access.

Above areas 1 and 2 are the main roof areas 4 and 5, which are clad with a reflective surface (i.e. high albedo) to minimise the heat gained from the sun and to maximise the protection of the area 1 and 2 occupants, from the sun's heat. This cladding may for example be a pre-coated roofing material with a light colour, preferably white or silver, and preferably with a glossy reflective surface.

Above area 3 is Sub-Roof 6, which is located at a lower height than main roofs 4 and 5. Sub— Roof 6 extends beneath 4 and 5 for some distance, so that in inclement weather it will maintain shelter integrity, capturing rain that is falling at a slant (rather than falling vertically) due to wind drift. This ement provides large ventilation air es 7 that are not compromised by a rain protection hood or similar airflow restricting ure. Sub—Roof 6 should preferably have a slope or slopes parallel to that of roofs 4 and/or 5, so that the main roof and of surfaces do not converge and constrict the ventilation gaps 7. By this design the usable space beneath of 6 is maximised without compromising airflow.

Sub-Roof 6 is clad with a low—albedo weather cladding, such as a pre-coated roofing al coloured black and preferably with a non—gloss matt finish. This surface absorbs the sun's radiation and becomes hot, conducting that heat to the air that is above it. The warm exhaust air from the building emerging from openings 7, passes over of 6, and thus is heated to a higher temperature. Being hotter, this exhaust air expands to a greater , is more buoyant, and rises more swiftly than had it not received that heat. As this heated air rises, more air must move in beneath it to replace it, and as Sub—Roof 6 is lower than main roofs 4 and 5, the replacement air is predominantly drawn from inside the building via openings 7 rather than being drawn from the external air above the main roof. The increased airflow being sucked out of exhaust openings 7 by the hot air rising from Sub-Roof 6 lowers the building internal pressure and thus draws in an increased amount of cooler outside—air through the building's ventilation inlets, which are d at low level in the ng exterior walls. Thus, the overall airflow through the building is increased by the action of the sun heating Sub-Roof 6.

The ventilation effect is to some extent favourably self-regulating. In colder weather the solar heat impacting Sub-Roof 6 is typically less, and hence, the ventilation-boost effect reduces. In this Page 3 of 6 colder weather, less airflow is desirable to avoid excessive cooling of the occupants, and so the airflow reduction is cial. Conversely, in hot r the airflow increases, which is beneficial.

As a refinement, the Sub—Roof 6 should ably have a sheet of reflective material such as aluminium foil, and/or insulation material, beneath the weather cladding. This s heat lost from the cladding underside, maximising the cladding temperature while also reducing the heat reradiating down onto area 3 occupants. The hotter cladding increases the ventilation—boost effect.

As a ment, Sub-Roof 6 ably should have a Ridge Vent, item 10 on the drawing, to exhaust the hot air accumulating under the Sub—Roof 6. This will further enhance the area 3 environment and also increase the overall upward movement of heated air above Sub-Roof 6, thereby increasing the overall airflow through the building. Sub-Roof 6 being of substantially smaller size than the main roofs 4,5, the ridge vent may be relatively small, and if required to prevent rain penetration, a conventional rain shielding method may be employed, such as the umbrella type hood illustrated at item 10. The hood should preferably be of a low-albedo al to maximise solar energy capture and heating of air above Sub—Roof 6.

As a further refinement to the building configuration, the main roof 5 on the side nearest the sun, which is not directly overhead in most latitudes, may be constructed lower than roof 4, so that Sub—Roof 6 has greater exposure to the sun and hence, increased ventilation-boost effect.

To adjust w for differing local climates, Sub—Roof 6 may be adjusted to differing heights by moving up or down its supporting columns, thus constricting or increasing ventilation exhaust gaps 7. For best rain protection and to minimise heat loss in cold weather conditions, Sub-Roof 6 will typically be set to the greatest height that will still achieve satisfactory ation in hot, still— weather conditions. Adjustment to se ventilation can be made at any time, after gaining experience with local climate conditions.

As a further refinement, a flow-restriction device 8 may be fitted to exhaust gaps 7 to reduce airflow on demand by the building manager. This could also serve to increase rain or sun-glare tion in extreme weather. Example devices could comprise: a hinged flap as illustrated on the drawing, raised and lowered by a remote actuating device such as a winch; or a flexible cloth type material deployed by rolling and unrolling on a drum or drums. The barrier face ("membrane") of the device may be an impervious construction such as sheet metal or transparent plastic, or may be a porous al such as shade cloth. A porous flow restrictor membrane would provide sun-glare protection over a higher proportion of openings 7 with less ction of airflow, making it appropriate for sunny climates. Conversely, an impervious flow restrictor membrane would more positively choke airflow, making it appropriate for cold climates (a transparent membrane may then be red, to let more light and heat in).

G AND DETAILS The drawing ns several arrows, the meanings of which are as follows: 0 The straight arrows impacting the or roof are solar radiation, "incoming". o The ht arrows entering and within the building, are fresh outside air flowing into and across the building. This flows mostly near floor level because cooler air sinks and runs beneath warmer air. 0 The convoluted arrows represent air that has been heated, and hence, is rising. o The size ofthe airflow arrows generally illustrates flow intensity.

Page 4 of 6 The exterior walls may be any types, provided that they have inlets for fresh e air, preferably at low level; alternatively, there may be supporting columns only and no exterior walls.

Sub-Roof 6 may be ted on columns by friction clamping or bolting to holes or fixtures, or the like, such that it can be adjusted up or down. The phantom outline and dashed arrow 9 illustrate the Sub-Roof being adjusted to a lower position to se gap 7 and thus increase airflow. The s may or may not form part of the support for the main roofs 4 and 5, or for other building feature. The n of the columns below the lowest extent of Sub—Roof 6 ment, may or may not incorporate dividing walls, but should preferably allow the passage of air at low level, to ventilate area 3.

The drawing depicts a typical building shape that is consistent with the various descriptions in this specification, but is not meant to construe any particular roof slope, size, shape, proportions, construction materials, or any other features other than those ically mentioned. For example, the building could be rectangular, circular, or any other shape within which the system described is capable of being employed; or the internal s may be omitted and Sub—Roof 6 suspended from a free spanning roof structure. The various elements of the drawing and descriptions in this specification broadly illustrate the invention but are not all-inclusive, and are deemed to include any equivalents known in the art which, if substituted, would not materially alter the substance of the invention.

Page 5 of 6 WHAT I

Claims (5)

CLAIM 1. IS (numbers in parentheses refer to the numbered features on the drawing)

1. A method to boost ventilation airflow h a building that is configured with a wide gap in the apex of the main roof or roofs (4,5) beneath which is mounted a sub-roof (6) that is overlapped by the main roof or roofs so that weather shelter ity beneath the main roof or roofs and the sub-roof is maintained and so that at least one large ventilation opening (7) extends between the main roof or roofs and the sub—roof from beneath the roofs to the wide gap. The claimed method to boost ventilation airflow in this configuration is to provide sub-roof (6) with a low albedo surface to receive solar radiation and thereby heat the air above the of, and thereby amplify the convection currents that are drawing air h the building and into the ventilation gs.

2. A method to enhance the ventilation boost effect in a building configured in ance with the method as described and claimed in claim 1, wherein a reflective material and/or insulation is fitted beneath Sub Roof (6), thereby redirecting back to the upper e of Sub Roof (6) the solar heat escaping from beneath.

3. A method to enhance the ventilation boost effect in a building configured in accordance with the method as described and claimed in claim 1, wherein a ridge vent (10) is fitted to the Sub- Roof (6) so that the hot air accumulating beneath the Sub—Roof (6) escapes to the zone above the Sub—Roof (6) and thus adds to the hot airflow rising above Sub-Roof (6), and consequently increases the overall building ventilation airflow.

4. A method to regulate the airflow on demand in a building configured in accordance with the method described and claimed in claim 1, wherein a remotely ted airflow restrictor (8) such as a hinged flap or a curtain, is installed in the ventilation opening/s (7), such that the barrier membrane of restrictor (8) partially closes off the ventilation opening/s (7).

5. A method to optimise for local climate the w restrictor (8) in a building configured in accordance with the method described and claimed in claims 1 and 4, wherein the barrier membrane material selected may have differing transparency and/or porosity, thereby restricting the passage of sunlight and/or air to a lesser or r degree, to best suit the d building interior environment in the prevailing climate conditions. Page 6 of 6 1 3 2