Method and Apparatus for Recovering of Transmitted Heat

The invention relates to a method and to an apparatus for recovering transmitted heat, for example, heat that is transmitted through the walls of a building. The present method and system is especially suitable for heating or air conditioning buildings with a more efficient use of energy.

Efforts for minimizing the energy consumption for the heating or air conditioning of buildings have been made heretofore. For example, European Patent Publication No. 115,014 discloses a method and a building construction for this purpose. The method and system in said European Patent Publication are rather efficient. However, it has been found that it nevertheless involves a substantial heat loss. The heat loss in the prior art is primarily caused by heat transmitted from the inside of a building to the surface of its outer walls where this heat is radiated into the atmosphere, thereby heating the atmosphere and causing a respective heat loss. This type of heat loss to the outer atmosphere is the larger the larger the temperature difference between the inside and outside of the building is across a single air circulating flow channel in the walls and roof of a building. There are practical limits which prevent reducing the temperature of the air circulating in the single air flow channel when the external temperatures are low.

German Pat. No. 2,929,070 (Bauer et al) discloses a system for reducing heat transmission losses through a building wall and roof quite similar to European Patent Publication No. 115,014, except the former reference discloses double air circulating channels in the roof. Valve means are so arranged that one or the other of the two parallel channels in the roof may be used in the air circulating system apparently for the purpose of passing the flow of circulating air either through the inner channel or through the outer channel. In the summer the air is circulated through the outer channel in the roof. In the winter the air is circulated through the inner channel in the roof. This feature is supposed to permit using the entire roof as a heat collector. A suggestion toward the claimed invention is not provided by this prior art teaching.

In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:

to provide a method and system which makes it possible to recover a substantial proportion of the heat that is being transmitted from a point of higher temperature to a point of lower temperature, for example, the heat passing through the walls, including the roof of a building;

to provide a method and system which are equally suitable for substantially reducing the heat loss from the inside of a building to the atmosphere or reducing the heat transfer from the atmosphere into a building, in other words, the present system and method are suitable for efficient heating purposes and for efficient air conditioning or cooling purposes;

to simplify an effective temperature control or temperature regulation including a rapid and precise follow-up temperature control or regulation;

to introduce the recovered heat fully or partially back into a building or the like; and

to provide a method and system which is even applicable to existing buildings for improving the efficiency of cooling or heating such conventional buildings.

The method of the invention achieves the above objective by the following steps. The surface of a body or volume such as a building to be heated or cooled according to the invention is enclosed at least partially by a first inner hollow space which in turn is surrounded by a separation wall. The separation wall in turn is surrounded by a second outer hollow space which is then enclosed by an enclosure wall having an outer surface in contact with the atmosphere. Fluid flow passages through the enclosure wall from the atmosphere into the second outer hollow space are located at elevational points as high as possible relative to the body or volume to be heated or cooled. Defined leakage is provided through the separation wall between the inner hollow space and the outer hollow space to assure a certain fluid communication through the separation wall. A suction device is used for keeping at least the inner hollow space at a reduced pressure relative to the atmosphere by sucking air out of said inner hollow space, whereby the air is heated by heat passing from the body or volume through the inner hollow space outwardly. The so recovered heat is returned to the body or into the volume.

In the prior art a single hollow space surrounding a building is used for keeping air in circulation with the aid of a fluid flow device such as a flow pump, whereby air from the inside of the building is added to the circulating air flow in the single hollow space. The invention departs from this prior art teaching by keeping the first or inner hollow space under reduced pressure relative to the atmosphere with the aid of a pump of a heat recovery system. The inner hollow space is connected to the outer hollow space by small flow passages which may be in the form of simple leakage paths through the separation wall between the two hollow spaces. By placing the fluid flow passages through the outer enclosure wall for providing fluid communication between the atmosphere and the outer hollow space, at elevational points located as high as possible, the normally colder and hence denser abmospheric air is thus caused to drop into the second outer hollow space. Thus, the normally higher density of the cooler air in the outer hollow space will naturally provide a higher pressure in the outer hollow space relative to the inner hollow space. This natural pressure difference is increased according to the invention by air removal from the inner hollow space. Accordingly, an air circulation in the inner hollow space around the building, as in the prior art, does not take place according to the invention. Rather, the present teaching establishes an air flow from the outside inwardly in a "radial" direction so to speak. As a result, the temperature difference between the outside atmospheric air and the air in the outer hollow space is almost, or substantially zero. This feature is desirable because it minimizes the loss of transmission heat through the wall structure.

The fact that the temperature in the inner hollow space is larger than the temperature in the outer hollow space is acceptable because any heat transferred through the separation wall into the outer hollow space is used for heating the air in the outer hollow space. The air heated in the outer hollow space is not dissipated to the outer atmosphere, rather, due to the enforced reduced pressure in the inner hollow space,the air will tend to travel inwardly in a substantially "radial direction", whereby any transmission heat taken up by the inward air flow is recovered by the heat recovering device. As a result, heat loss to the outer atmosphere is minimized to an optimal extent.

Due to the optimal reduction of the heat loss, it is possible to correspondingly reduce the total energy input needed for heating the inside of a building. The heat output of the devices used for heating the inside of a building can be correspondingly smaller. For example, proper piping used for a floor and/or ceiling heating system can have inner diameters in the range of about 6 mm to about 8 mm. As a result, costs for such systems are substantially reduced, especially also since the installation of smaller diameter pipes is simplified. Another advantage of such a system is seen in that the lead or system temperature can be approximately within the range of the desired room temperature. In other words, the system temperature does not need to be much higher than the desired room temperature because the temperature gradient between the surface temperature of the surfaces being heated and the temperature in the room can be very small. For example, a floor heating system can keep the floor temperature close to the desired room temperature even if the outside temperatures are very low. Another advantage is seen in that due to the small heat losses, it is possible to use a heat pump in a heat recovery device which is small in its dimensions and it can be operated at an optimal or advantageous efficiency.

Under optimal conditions an equilibrium may be achieved between heat trying to escape and the heat that is being recovered. The method according to the invention is also suitable for substantially preventing or reducing the loss of heat by the surrounding atmosphere to the building. In other words, the present method can be used for air conditioning a building when the external temperature is higher than the temperature desired for the inside of a building. In this instance, heat flowing from the outside through the hollow spaces into a building is recovered in the same way as when the system is used for heating purposes, however, rather than returning the recovered heat into the building, the recovered heat is returned to the atmosphere. The air from which heat has been recovered, may in this instance be used either directly or indirectly in a heat exchanger for cooling the inside of a building. Thus, it is possible, if desired, to even reduce the internal temperature in a building. Even if the external temperature and the temperature in a building are initially equal to each other, but there are many people in a building generating heat, it is possible to avoid an increase in the internal temperature of a building by removing heat with the present method. In this instance hot air inside the rooms of a building are sucked out, heat is being recovered from the sucked out air, and the sucked out air is replaced by fresh air from the outside having a temperature lower than the inside temperature. Heat recovered in this manner can be used for heating structural masses of a building, for example, its basement floor or its foundation where the heat may be stored for later recovery and used for heating purposes. The recovered heat may also be used, for example, for heating water to provide hot water for the building. Another possibility of storing the recovered heat in these instances is to insulate the soil around a building and to install in the soil ducts for heating the insulated soil and to recover the so stored heat at a later time.

The system according to the invention for performing the present method comprises a hollow body such as a building having at least one inner hollow volume with at least one inner collecting shaft or duct inside the hollow volume. One end of the hollow duct is connected with the suction side of a heat recovery device and the other end of the hollow shaft or duct is connected to the hollow volume in the building which is surrounded at least to a substantial extent of its outwardly facing surface by a first hollow space which in turn is surrounded by a separation wall. The first hollow space is connected with the collecting shaft or duct. The building is equipped with heat exchangers which in turn are connected to the heat exchangers of the heat recovery device. The separation wall is in turn surrounded by a second hollow space which is enclosed by an outer enclosure wall having an outer surface facing the atmosphere. The first and second hollow spaces are provided primarily around a zone of the building reaching into the atmosphere. Defined leakage passages or ducts are provided between the inner first hollow space and the outer second hollow space through the separation wall. The first hollow space and the volume inside the building are connected through the collecting ducts with the suction side of the heat recovery device. This connection may comprise controllable means for controlling the air flow. The suction device produces a continuous reduced pressure inside the building volume and inside the first and second hollow spaces relative to the atmosphere. Fluid flow passages located at elevational points as high as possible relative to the building, connect the atmosphere to the second outer hollow space so that the surrounding air of the atmosphere can enter through these fluid flow passages into the second outer hollow space and,due to the reduced pressure, through the leakage ducts into the inner hollow space, whereby the atmospheric air takes up heat from the heat passing from the inner volume of the building outwardly through the hollow spaces and through the separation wall.

This just described structure according to the invention encloses substantial zones or surface areas of a building with the two hollow spaces in double layer fashion so to speak. The air volume or masses in these two hollow spaces are not kept in circulation by a pump, but rather, are sucked off by a suction pump of the heat exchanging device. The construction of such a building is very simple and no special requirements need to be met by the mentioned inner and outer hollow spaces. Even the shape of these hollow spaces is not critical because the flow speed of the sucked off air is very small for an effective recovery.

In order that the invention may be clearly understood, it will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a simplified sectional view in a horizontal plane through a body or building constructed for performing the method according to the invention;

FIG. 2 is a vertical sectional view through a private dwelling constructed according to the invention;

FIG. 3 shows a detail sectional view through a portion A of a floor and ceiling structure in FIG. 2, illustrating the arrangement of a ceiling and floor heating system;

FIG. 4 is a detail sectional view through a portion B of a wall structure shown in FIG. 2;

FIG. 5A is a detail of the wall structure primarily of the separation wall between the first inner and second outer hollow space and between the inner hollow space and the inner volume of the building;

FIG. 5B is a sectional view along section line 5B--5B FIG. 5A; and

FIG. 6 is a block diagram of the energy flow in a system according to the invention.

The horizontal section through a body 10 shown in FIG. 1 may symbolize any type of enclosure, such as a building, a pipeline, a container or the like. An inner volume 16 is enclosed by a conventional interior wall 16' which in turn is surrounded by heat insulation 38. The heat insulation 38 is surrounded by a first inner hollow space 1 which may be divided into a plurality of flow channels 1' by spacer members 40. All the flow channels 1' communicate with one another for an evacuation. A separation wall 3 separates the first inner hollow spaces 1 from a second outer hollow space 2. The separation wall 3 may be constructed as a double wall having an inner heat insulating portion 3' and an outer structural portion 3" both of it maybe of the same material. The second outer hollow space in turn is enclosed by an outer enclosure wall 13 having an outwardly facing surface 5. The wall components 16', 38, 3', and 3" are constructed of structural elements 27 so arranged that defined leakage paths 15 are provided between the inner volume 16 and the first hollow spaces 1, here in the form of the flap 31a as well as between the inner hollow spaces 1 and the outer hollow space 2. The structural elements 27, shown in FIG. 5A are made to include heat insulating features. The leakage channels 15 may be holes or slots existing between the abutting surfaces of the element 28 which provides for the required flow communication.

Inlet ducts 14 through the outer enclosure wall or skin 13 permit the atmospheric air to enter into the outer hollow space 2. For this purpose the ducts 14 are located at an optimally high elevation relative to the structure 10 such as a building to enhance the entry of the atmospheric air into the hollow space 2 connected to the hollow space 1 through the mentioned defined leakage channels 15. The inner hollow spaces 1, 1' are connected to a channel 41 which in turn is connected to the suction port of a heat recovery system 7, 7', and 8. The discharge port 35 of the heat recovery system delivers cooled or heated air, for example to the atmosphere. Heat exchanger means 22 located in the inner volume 16 are connected to the heat recovery system 7, 7', and 8. Thus, heat may be supplied into the volume 16 or heat may be withdrawn from the volume 16 through the heat exchanger 22.

The schematic view of a building shown in FIG. 2 shows that the entire volume 16 of the building 10 is enclosed by two hollow spaces 1 and 2 in the building walls including in the roof 32. The roof 32 is considered to be part of the outer wall 13 and coin function as contain a solar collector. The hollow spaces 1 also extend through the mass of the foundation 17 in form of a plurality of pipes. The spaces 18 enclosed by the foundation are normally not heated. The foundation 17 extends down into the soil 19. If desired, the means for forming the inner and outer hollow spaces 1 and 2 may run on the outside of the foundation wall 17 as shown in the left-hand part of FIG. 2. Thus, the two hollow spaces 1 and 2 could be located between the foundation wall 17 and the soil 19, for example, if an existing building is to be improved in accordance with the present teaching.

A central collecting shaft or duct 21 extends inside the building passing from the basement 18 through the living quarters 16 and 20. A heating unit 45 is mounted in the shaft or duct 21. Ducts or energy supply lines 46 connect the heating device 45 to a source of energy such as a boiler not shown. Any conventional heating device is suitable and the heating device may be controlled, for example, through a thermostat as is customary.

The heater 45 may, if desired, be used for supplying heat to the heat pump 7' through a heat exchanger 7 as indicated by the dashed line 45'. The interior of the duct 21 is connected with the inner hollow space 1 in fluid communication as indicated at 1". Further, the inner volume 18 is connected with the duct 21 through adjustable vents 31. Similarly, the inner volumes 16 and 20 are in fluid communication with the inside of the shaft or duct 21 through respective adjustable vents 31. The fluid communication between the inner hollow space 1 and the shaft 21 is preferably located near the basement floor, or at least in the zone of the foundation 17.

An adjustable control flap 31b located inside the duct 21 is used for controlling the pressure and throughput distribution between the medium proportion sucked out of the volumes 16, 18, and 20 on the one hand, and the volume sucked out of the inner hollow space 1 on the other hand. The suction is accomplished by a ventilator 8 which forms part of the heat recovery system including the heat pump 7' and the heat exchanger 7. A humidifier 47 is connected through a conduit 49 to the suction inlet of the heat exchanger 7 for supplying moisture to the air sucked into the heat recovery system. If desired, heat may also be supplied through the humidified to the air sucked into the heat recovery system. The humidifier 47 has an inlet 48 connected to a water main or the like. The operation of the humidifier 47 is controlled by a respective control mechanism of conventional construction and responsive to the relative humidity. The humidifier 47 and the heat recovery system 7, 7', and 8 are preferably located in the basement, that is, in an inner volume 18 that is not heated. The heat recovery system 7, 7', 8 is connected with an air discharge conduit 35 leading, for example, through the basement wall 17 to the atmosphere through a manhole 12 or the like. As shown in FIG. 2 heat exchanging system is provided as a system, comprising for example two heat exchangers 7, two compressors or heat pumps 7', two ventilators or fans 8 and respective expansion valves not shown as well as only one of each part but more than one compressor. The two systems are connected in series or in parallel with regard to the air coming from the heat exchanger 45 as shown in FIG. 2. The parallel connection is provided by the duct 45". Heat recovered by the system 7, 8, 7' is supplied through a pipe or conduit 36 and through a circulating pump 34 to a further heat exchanger 33 which may, for example, heat a hot water supply or a swimming pool or the like. An output conduit 36' of the heat exchanger 33 is connected to heating pipes 23 forming a heater in a floor 22 or land in a ceiling 22' as will be described in more detail with reference to FIG. 3. The heat transmitting fluid may, for instance, be water pumped by the pump 34 through the pipes 23 and through a return pipe 37 back to the heat recovery systems 7, 7', and 8.

FIG. 3 shows, on an enlarged scale, the detail A of FIG. 2 illustrating a floor 22 and a ceiling 22'. The structural details regarding the strength of the structure are not shown, since they are conventional. A heat insulating layer 43 separates the floor heating pipes 23 from the ceiling heating pipes 23'. The floor heating pipes 23 are embedded, for example, in a suitable floor forming substance, such as a layer 24 of concrete or the like. The ceiling heating pipes 23' are embedded in a similar layer 24', for example, of plaster of paris. It has been found that relatively low heat quantities must be transported for maintaining the temperature in the volumes 16, 20. Thus, the temperature gradient between the room temperature and the water flowing through the heating pipes 23, 23' may also be very small. As a result, the heating pipes 23, 23' may have a smaller inner diameter than heretofore. It has been found that a diameter in the order of 6 to 8 mm is satisfactory. This has the advantage that the installation of the pipes 23, 23' is greatly facilitated. Costs are respectively reduced. Copper or plastics material are suitable for the pipes.

The enlarged illustration of FIG. 4 shows a detail B of the wall construction. The structure is substantially the same as shown in FIG. 1. However, FIG. 4 shows the leakage duct 15. The outer wall 13 may, for example, be constructed as a brick veneer wall. The inner wall 39 builded inwardly of the wall 16' may, for example, be made of building blocks. The inner wall may also be constructed of bricks. The separation wall 3 is constructed as described above with reference to FIG. 1. It is desirable that as much of the structure of a building projecting above the ground level should be enclosed by the outer enclosure wall 13 to form the second outer hollow space 2. This hollow space 2 may also be subdivided into a plurality of channels similar to the channels 1' formed by the studs 40. Such separating studs may also be inserted between the brick veneer 13 and the outer section 3" of the separation wall 3. In any event, all the channels of the hollow space 2 would communicate with each other. In connection with existing buildings the wall portion 16' may be a stucco layer to which the heat insulating layer 38 is applied by conventional means. Hard foam tongue and groove panels may form the two heat insulating layers 38 and 3' and such panels may be interconnected as standard structural items by the studs 40. Any conventional way of assembly is suitable, for example, brackets or adhesives or interlocking hardware may be used. The inner volume such as the rooms 20 are connected to the inner hollow space 1 through a duct 29 passing through the wall structure 39. A flow control flap 31a is arranged in the duct 29. The flap 31a is shown in the duct closing position. The flap control motor 30a for opening and closing the flap 31a is responsive to the pressure difference in the inner hollow space 1 and the inner volume. Thus, the volume flow can be controlled in accordance with the desired pressure difference. For practical purposes this pressure difference should be about to 20 pascal.

Basically, the structure shown in FIG. 4 can also be used in the construction of the roof 32 shown in FIG. 2. The vents between the atmosphere and the second outer hollow space 2 will be located at elevational levels as high as permitted by the building. FIG. 2, for example, shows that a ridge vent 14 connects the outer second hollow space 2 with the atmosphere so that the external air can enter into the outer hollow space 2. Due to the construction of the invention which provides defined leakage between the second outer hollow space 2 and the first inner hollow space 1 through the partition wall 3 and since the first inner hollow space 1 is under reduced pressure, the air travels "radially" from the outside through the space 2, through the defined leakage ducts 15, into the hollow spaces 1, and from these hollow spaces 1 into the heat recovering system 7, 7', 8. Thus, in a system according to the invention, the air does not circulate in these hollow spaces 1 and 2, but rather, passes through these hollow spaces. As a result, heat that wants to travel from the inner volume 16, 20, 18 outwardly, will heat the air coming into the inner hollow space 1. The heat taken by the inner hollow space 1 is then recovered by the heat recovery system 7, 7', 8. Normally, the temperature of the air in the second hollow space 2 will be lower than the temperature in the first hollow space 1. Thus, even the air in the second hollow space 2 can take up heat that wants to travel outwardly. However, the temperature gradient between the first and second hollow spaces 1 and 2 will be relatively small and the heat transfer will be respectively small. It has been found, that most of the heat still trying to travel outwardly through the hollow space 2 is recovered, particularly along the outer surface of the outer wall portion 3" and because the air travels inwardly due to the pressure differential across the defined leakage ducts 15. In conventional structures in which there is only one air circulating duct enveloping a building, such heat that passes through the envelope is lost in prior art structures. The invention avoids such heat loss.

FIGS. 5A and 5B show the construction of the separation wall 3. The controlled leakage is provided by tubular members 15 passing through all wall portions 16', 38, 3', and 3". The leakage is also provided along the joints 15' between the structural components or panels 27 forming the walls. Conventional hardware elements 42 may pass through the tubular members 15 for mounting the separate wall members or elements in place.

As mentioned above, the present system is also suitable for air conditioning when the temperature of the atmospheric air is higher than the temperature desired in the inner volumes 16, 18, and 20. In that case, the air in the second outer hollow space 2 will be warmer than the air inside. As a result, transmission heat will pass through the control leakage ducts 15 from space 2 into space 1, whereby transmission by direct radiation through the separation wall 3 is also possible. The so warmed air will also be sucked out of the hollow spaces 1 until the temperature in the hollow space 1 reaches the temperature in the inner volumes, whereby further heat transport from the outside into the inner volumes is stopped because there is no further temperature gradient between the temperature in the hollow spaces 1 and the inner volumes 16, 18, and 20. The heat recovered from the spaces 1 is returned to the atmosphere. The operation is the same as when heat travels from the inside outwardly. In the latter case the heat is returned into the spaces 16 and 20 for heating purposes. If heating is not required, the recovered heat may be used for heating the water supply or a swimming pool or the like. Such heating may take place in both instances, regardless whether the heat is recovered due to the outside temperature being higher or due to the inside temperature being higher. The cooled down air is passed through the outlet conduit or duct 35 through the manhole 12 to the atmosphere.

The method and apparatus according to the invention avoid heat loss substantially completely. Therefore, the power rating and power consumption of the heat recovery system can be surprisingly low. A further advantage is seen in the fact that the heat exchanger 22 and the respective heating systems in the floor and/or in the ceiling must transport relatively small heat quantities. As a result, smaller diameter pipes may be used for these heating systems as mentioned above. Moreover, the temperature difference between the heating system and the rooms to be heated or cooled can also be kept at an optimally low value since small heat quantities need to be transported. As a result, the respective heat pump 34 can also have a low power rating at which the heat pump may operate at optimal efficiency.

FIG. 6 shows a heat flow diagram of a system according to the invention. Heat passing from the inner volumes 16, 20, through the enveloping structure is recovered in the evaporator of the heat recovery system which also receives heat from the inner volumes directly. The cooled air is discharged to the atmosphere and the heat is passed to the condenser driven by, for example, an electrical motor and the condenser transmits the heat to the floor and/or ceiling heating system which in turn heats the inner volumes. Thus, it will be seen that the system according to the invention involves a substantially closed heat circulating system. Temperature control is achieved by regulating the air flow or by invading the closed circuit as indicated by the inputs of atmospheric air into the inner spaces 1 and 2 of the enveloping shell of the structure.

The present system is also well suited for using the structural substance of a building for heat storage and such storage may even be extended to include the surrounding soil. Thus, the building mass and the surrounding soil may be used as heat buffers. It is desirable to reduce the temperature of the air sucked out of the hollow spaces 1 to the temperature of the atmospheric air to keep the temperature gradient between the atmospheric air and the air in the hollow space 2 as small as possible, or preferably at zero. As a result, the respective heat pump can work in an optimal range. By providing the ability of supplying recovered heat to the outside, the resulting cooled air can be used for air conditioning purposes. The temperature control is especially simple by merely controlling the throughflow, for example, with the control flaps shown at 31a and at 31b.

By providing the heat content or inner energy of the fluid to be heated and of the heating fluid to be substantially equal to each other, it is assured that the control requirements are substantially simplified and heat losses are avoided. This feature also has the advantage that a follow-up control or regulation can be achieved quickly and precisely to hold, for example, the room temperature at a constant value.

Due to the efficient heat recovery achieved according to the invention, the above mentioned pipes for ceiling and/or floor heating systems can be inexpensive, whereby the construction costs are reduced compared to the prior art. The construction costs are further reduced because the heat pump or pumps according to the invention may be smaller than was needed heretofore. By arranging several heat pumps in series, the heat pumps may be progressively smaller in their capacity so that, depending on requirements, one or more heat pumps may be used.

For new buildings it is possible to use structural components which already have the two hollow spaces built in, so to speak, including the leakage paths 15. In existing structures the two channels may be formed by intermediate separation panels and by an outer veneer wall. Thus, the invention is very versatile in its application to new and existing structures. In any event, factory produced structural components may be used for the present purposes, whereby the required heat insulating layers are integrated into such structural components in an inexpensive manner.

By using hallways and stairways for the central hollow shaft or duct 21, building costs are further reduced as far as the present purposes are concerned. Similarly, an existing flue may be used for drawing external air into the building and preheating such external air.

By properly placing the flow volume control members such as 31a and 31, it is possible according to the invention, to individually control the heat in any of the rooms of a building.

The roof structure may be such that it forms a so-called "air collector" which is connected with the first hollow space 1 either directly or through a flow control device. Thus, with the aid of such an "air collector" it is possible to influence the temperature and reduced pressure in the hollow space 1 in a simple manner. The thus recovered solar energy can be used for heating purposes, for example, heating a swimming pool.

By placing a heat exchanger into the lead pipe of a heating system, as taught herein, the continuous operation of a heat pump at a relatively low power rating, and at an advantageous efficiency is achieved in an economical manner since any excess heat is used in such a heat exchanger without adversely affecting the desired room temperature. Any hot water that has been used in the building can also be passed through a further heat exchanger to recover heat of the used water. By properly controlling the air flow, for example, at 31a and 31b, it is possible to influence the volume and reduced pressure in the inner space within certain limits in such a way that the power rating and efficiency of the heat pumps is advantageously influenced. More specifically, the adjustment flap 31b can effectively control either manually or in a closed loop circuit the volume throughflow through the heat pump.

Although the invention has been described with reference to specific example embodiments, it will be appreciated that it is intended to cover all modifications and equivalents within the scope of the appended claims.