The present invention relates to a ventilation and heat recovering system in buildings, and it is the purpose of the invention to provide such a system, which has the advantage of a great simplicity and a high efficiency, viz. by having an appreciable efficiency without requiring separate energy supply.

The invention is based on the consideration that in heated building rooms a certain amount of overheated air is normally present underneath the ceiling, and that a certain part of this heat is expliotable without dramatic side effects, when a certain, modest ventilation is desired anyway. Such an exploitation may be effected without any other energy supply than the one coming from an outer wind effect on an exhaust and/or air intake valve, which when mounted on a roof is almost always able to produce a costless air exchange of an appreciable magnitude in one or more connected rooms. Thus, by means of an ordinary exhaust hood placed in a certain height, it is easy to provide an air exchange of 30-50 /h by a very light wind, and even though this is not comparable to motor driven ventilation systems, an exploitable effect is nevertheless concerned, through which it is possible to take advantage of modest interior heat resources, which will normally be too small to be profitably exploitable at all.

Thus, if the warm air underneath the ceiling was removed by great capacity, this would imply a considerably increased heating requirement for continuous build-up of this warm air cushion, but if it is exhausted slowly corresponding to a desired, relatively low degree of ventilation in the room, the concerned heat will be exploitab ^' Js in an economical manner, when the associated equipment is ^' • cheap to procure and costless in operation. Thus, it is hereby within reach to exploit small heat resources which have not been

economically exploitable hitherto.

By the invention care is taken that the ventilation air exhausted from the heated room is collected from the area immediately underneath the ceiling and conducted through a heat exchanger for heat exchanging with fresh air, which is conducted through a pipe from an outer intake valve to another room, wherefrom air is exhausted through a draught hood. The heat in the discharged air from the first room may hereby be exploited for co-heating the second room, or optionally more rooms, which are weakly ventilated.

It may even be provided for that the sucked out or pressed out warm air is conducted through a filter for direct intermixture into the fresh air flowing to the other room or rooms, whereby the discharge heat is totally exploited. Also this influx may be effected solely by a natural air flow produced by wind effect on a roof mounted draught and/ or pressure hood, i.e. without operation costs. It must then be accepted that the ventilation and heat recovering system will be inactive on days of total wind still, but here only a very few days of the year are concerned, as there is almost always wind at the roof level, also when there is no wind at ground level.

This is also to be viewed on the background that with its very low installation and operation costs, the concerned system cannot actually be expected to have such a heat recovering capacity that it is able to substantially reduce the required capacity of the used heating system, but only to contribute to lowering the operation costs thereof in a profitable manner. Hereby it will be of no special impor- tance that the system according to the invention will be inactive a very few days of the year, the existing heating systems then merely being required to operate with a correspondingly increased capacity.

Generally it applies that in construction technique almost opposite ventilation concepts are applied, as either a real ventilation is neglected, or very efficient, power-driven systems are prescribed which are expensive with respect to both installation and operation. By the invention it is recognized that in far most cases a compromise is sufficient, by which the ventilation and an optional, corresponding heat recovering may not meet ideal requirements or possibilities, but are nevertheless significant. Such a decisive and in many cases fully sufficient improvement is practically obtainable already through the existing natural forces, viz. the occurring wind energy which may be used for respective impression and exhaustion of air to and from the building rooms, and the tendency of the heated indoor air to rise. Furthermore, an appreciable energy supplement is obtainable from a simple solar cell unit for a direct heating of the drawn-in fresh air. By the invention it is essential that the ventilation hoods which produce the air exhaust as well as the air intake be placed at the roof level of the building, as greater wind forces occur here than at ground level, i.e. there is generally more wind energy present that immediately conceivable at ground level.

It is very well known to terminate various erect ventilation conducts by a top hood, the essential function of which is to protect the conduct from down-falling rain water. Hitherto it has not been used additionally to design the hood specially for producing a specialized air suction or pression effect depending on the occurring wind, and easurings effected on erect ventilation conducts having conventional top hoods have shown that arbitrarily rising and falling air movements have occurred in the conducts, i.e. it has not been specialized pressure or draught hoods.

In connection with the invention the free wind force is used as a primary motive power in the ventilation system, and top hoods have been developed which are specialized for effecting

a draught effect and a pressure effect, respectively, such as it is explained in more detail below.

In the following, the invention is described in more detail with reference to the drawing, in which

Fig. 1 is a perspective view of a draught hood according to the invention.

Fig. 2 is a corresponding view of the mounted hood.

Fig. 3 is a perspective view of a pressure hood according to the invention, Fig. 4 is a schematic view of a ventilation system according to the invention, and

Fig. 5 is a side sectional view of a solar cell unit built into the system.

The draught hood shown in Fig. 1 is shaped in plate material as a triangular hat 2 having closed end gables 4, which at a lower end 6 project slightly further downwards than the oblique walls 8 of the hat. At the bottom the gable portions 4 are terminated by an inwardly and slightly upwardly bent plate portion 10, which i.a. functions as a condense groove. A plate-shaped fastening fitting 12 is fastened to the lower end of each oblique wall, which plate fitting is bent inwards and slightly downwards from the bottom edge of the oblique wall and thereafter straight downwards in a vertical plate portion 14, which may be fastened to opposite sides of an upwardly conducting ventilation pipέ. The plate fitting 12 extends a certain distance in the upwards direction along the inner side of the oblique wall, which strip is slight¬ ly inclined relative the horizontal orientation, such that a condense groove is provided which may conduct condensed water from the oblique wall out to one or both of the gable grooves 10.

Each of the oblique walls 8 is provided with a pair of

horizontal gill slits 10 underneath superjacent protruding rib portions.

These gill slits and the plate members projecting inwards at the bottom are seen to have the effect that wind which sweeps over the hood 2 produces a partial vacuum inside the hood and therewith a controlled, active suction effect on the ventilation pipe, which is designated 20 in Fig. 2. For obtaining this unequivocal effect it has proved to be important that the gable walls have additional downwardly projecting lower portions 6. The effect is pronounced, regardless of wind direction. An exact explanation for the unequivocal obtention of a suction effect in the ventilation pipe is difficult to provide, and it is deemed unnecessary here to provide a closer explanation, given that the effect occurs notoriously.

The pressure hood 22 shown in Fig. 3 is designed in an extensively corresponding manner, but without gill slits, and having an additional, subjacent element being a round- going coilar 24, which is oblique in the inwards and upwards direction, this collar surrounding the upper end of the ventilation pipe, here designated 26. The collar guides the wind into and up into the hood 22, regardless of wind direction, and the inwardly projecting hood portions in the lower area of the hood have an inhibiting effect on air outflow, such that an overpressure is built up in the hood and a downwards conducting of the air occurs in the ventilation pipe 26, also here with a significant unequivocability as to the air direction in the pipe. Thus is provided an "inhaust" hood which is active even by weak wind.

When the two hoods are placed at opposite ends of a venti¬ lation system, this may function without using artificial energy. By using only one hood a certain, however less pronounced,ventilation effect is still obtainable, and if

the other hood may be replaced by an exhaust valve or an intake valve, respectively, placed in the wall of the ventilated room or rooms.

As mentioned it is important that by the sought slow ventilation a certain excess heat in the building is usable for increasing the temperature of the supplied fresh air. In the present invention the further step is taken that by the concerned "natural ventilation" which is efficient relative to installation and operation costs, it is quite possible to obtain a costless heat supplement by means of a simple solar cell unit cooperating directly with the supplied fresh air. In usual, deliberately highly efficient heating systems a weak air flow through a solar cell uni will hardly be particularly attractive, but given that in connection with the invention associated operation costs may be disregarded entirely, this ^• possibility is attractive, as such a solar cell unit may be produced in an extremely simple manner. An air temperature increase of a very few degrees will be profit- able, when the increase concerns the air which is sent into the rooms of the building, directly or through a simple heat exchanger.

The inventiondeterminedly concerns a high relative efficiency as to room air ventilation and heating, and the solar cell system is not, as normally, to be adaptable for contributing also to e.g. the hot water supply, which requires a far more complicated installation by which it is not at all possible to exploit a heat supplement of only very few degrees in an brought-in, relatively weak air flow.

For that matter it is an important possibility in connection with the inventionthata supply may be established of more or less pre-heated ventilation air, which is heated by being pressed or sucked through a solar cell unit by means of a pressure hood or a draught hood, respectively.

or preferably both a pressure hood and a draught hood, i.e. optionally without the air being additionally heated by heat exchanging with discharged warm air, from the ventilated room or rooms. If the air is pressed in through the solar cell unit by means of a pressure hood without the ventilation being supported by exhausting room air through a draught hood, a ventilation will still occur inasfar as the pressed-in air will leave the room through natural openings or through an outlet valve, and inversely, a draught hood may create such a low pressure in a room that a

-suction may be established through a solar cell unit without the air passage through the solar cell unit necessarily having to be supported by an active pressing from a pressure hood. However, it will be appreciated that the efficiency of the system is improved in a both decisive and cheap , manner by using both a pressure hood and a suction hood for the respective purposes. However, a combination system may well be considered, in which exhaustion is effected by one or more draught hoods, while a pressing in of outdoor air takes place through separate pressure hoods for air supply to the building through a solar cell unit, respectively a box for preheating the incoming air by heat exchanging with out¬ going warm room air.

As known, it is an aim in modern house building to make habitations both air-tight and well heat insulated, while an associated, entirely necessary ventilation is a stepchild in this development. Either there is practically no ventilation, which creates considerable indoor climate problems and entails an accelerated decay of the buildings, or motor- driven systems are used which create other types of problems, viz. noise and draught inconveniences as well as high installation and operation costs .which are very close to making up for the energy saving which is obtained by constructing the buildings in the air-tight and well insulated version. Extremely great financial investments are concerned here, and from both points of view it is a

high-carat aquisition that the invention provides for establishing a ventilation system which is very cheap in installation andmaintenance, and simply costless in operation, and yet able on almost all days of the year to provide for a sufficient ventilation for a good indoor climate, i.e. with a room air exchange which is sufficient from both physiological and building-preserving points of view, and which may be effected in a both noise- and draught- free manner entirely without using "pay energy". It is without real importance that the system will be inactive a very few days per year, where there is no wind at roof level, inasfar as it is already acceptable that many habitations are without particular ventilation all year long. In practice there are only a very few days per year of such an absolute wind still.

Thus, the invention is advantageous already considering the ventilation problem alone, but as, moreover, a preheating of the ventilation air is effected by the invention by means of either out-going warm air or solar heat or both, it will be appreciated that to a very large extent, the invention also touches heating economy on a national scale, and as habitation heating at these latitudes is a major economic problem, the invention will thus be correspondingly ex¬ tremely important.

Such a combined ventilation and pre-heating system is shown in Fig. 4 in an embodiment, where a draught hood 2 on an exhaust conduct is connected with a lower area of a heat exchanger box 32 which is well heat insulated and connected at its top at the opposite side to an inlet conduct 34 connected to an inlet nozzle 36 at a ceiling area at which relatively warm room air is present, e.g. above a wood- burning stove or a radiator. The warm air will seek upwards naturally through the conduct 34 to the upper part of the box 32, but of course this rising will be intensified

considerably by the effect of the draught or suction hood 2, which will thereby also cause the warm air to be drawn downwards in the box 32 to the low outlet for the conduct 30.

In the box 32 is placed a U-shaped hose element 38 of thin aluminum foil, preferably corrugated, which uppermost to the left is connected to a downwards conduct 40 from the upper end of a roof mounted air solar cell unit 42, the other, lower end of which is connected to a pressure hood 22. Uppermost to the right of the box, the U-hose 38 is connected to a conduct 44 extending downwards to a nozzle

46 for supply of ventilation air to one or more building rooms, Through the pressure hood 22 the fresh air is pressed through the solar cell unit and through the hose 38 for delivery through the nozzle 46, and the air will thus be heated both by the solar cell unit and by the warm exhaust air in the box 32.

It has been found that an indoor air exchange of only half a time per hour is sufficient for assuring both a good, draught-free living climate and a good building preservation, and in practice this is obtainable by means of the invention, which may also substantially reduce the heating costs during the cold period. The system may be constructed such that it is practically maintenance free, without motors and without control or regulation means of any kind, except for optional, manually operable throughlet valves. The solar cell unit may be efficient even when not larger than a normal tipping roof window, and it may optionally be provided with a valve, by means of which it can be put entirely or partially out of operation during summer.

An example of such an air solar cell unit is shown in Fig. 5. It is a flat box connected to one or two pressure hoods at one end and having a glass top side and a black, undulated intermediate plate element which extends over the entire

width of the box, but ends at a certain distance from both ends of the box. At the opposite end of the box and in its bottom is provided an outlet opening for connection with the downlet conduct 40, and in the end wall is placed a valve which may be opened during summer. During operation the air will flow longitudinally in the box on both sides of the heat catching intermediate layer, and as the air velocity is moderate or low, it is quite possible to obtain a consider¬ able air heating also during the cold season.

It is to be mentioned that the pressure hood should be placed a short distance downwards on the roof on the side oriented towards the prevailing wind direction. Ideally there may be one or more hoods on each side of the roof; these may be jointly connected to the downlet conduct, but in that case diaphragm valves or other self-operating, simple devices should be used as countervalves in the respective conducts to ensure that the air pressed in from the active hood or hoods is not just blown out through the opposite pressure hood or hoods.

Of course the invention is not limited to any specific design- of the used air/air-heat exchanger, but for the sake of good efficiency by the occurring relatively weak air flows it should be considered that the exchanger should have a certain blocking effect against a free convection draught of the warm air from the nozzle 36, such that its heat is optimally exploited.