NO321847B1 - Method and device for ventilation of foundations - Google Patents

Abstract

Arrangement for protecting floors above the crawl space and buildings on foundations of the crawl-space type from damp and microbial growth, where the crawl space (2) is delimited by the floor (4) above the crawl space of the building, bearing foundation walls (1) with vents (9) for outdoor air and the foundation ground (3). The arrangement comprises an essentially windtight and vapourtight climate screen (12) which is arranged in such a manner that it divides the crawl space (2) into at least one upper (10) and at least one lower (11) climate zone and forms a tight partition between the climate zones. The climate screen (12) is located at such at height in the crawl space (2) that the outdoor air vents (9) in the foundation walls (1) communicate with only the lower climate zone (11). The upper climate zone (10) is provided with at least one supply air opening (18) which is connected to a room above in the building, and an exhaust air opening (21; 22) which is connected to a discharge duct (23; 24). A fan (25) is arranged in association with the discharge duct (23; 24), by means of which it is possible to maintain a lower pressure in the upper climate zone (10) than the pressure in said room above, so that the upper climate zone (10) is ventilated by indoor air from the building and the lower climate zone (11) is ventilated by outdoor air. The invention also relates to a method of protecting the floor above the crawl space from damp and microbial growth.

Description

The present invention relates to a method for protecting floors above crawlspaces and buildings on crawlspace-type foundations against moisture and microbial growth, where the crawlspace is delimited by the floor above the crawlspace in the building, load-bearing foundation walls with ventilation holes for outside air and the base of the foundation.

The invention also relates to a device for use in application of the method.

Building foundations of the crawl space type, i.e. foundations where there is a crawl space between the floor of the building and the base of the foundation, which crawl space is delimited in the lateral direction by load-bearing foundation walls, have traditionally been ventilated by outside air via air holes placed in the foundation walls. Foundations of this type have worked in the past, one of the reasons for which is the fact that chimneys extend through the floor above the crawl space and down into the crawl space, which thus contributed to heating and drying the foundation and the air inside. A certain degree of heat leakage into the crawl space from the room above also took place as a result of poor insulation of the floor above the crawl space. This, combined with correctly carried out ventilation, meant that it is possible to avoid problems with moisture and mould.

Since crawl space foundations ventilated with outdoor air constituted a cost-effective foundation method, this method is used during the second half of the twentieth century in mass production of residential houses and also for other buildings, especially prefabricated schools and the like.

In this context, problems arose that are difficult to solve, as a result of moisture in the foundation, which caused micro growth, unpleasant odors and rotting damage to the buildings.

The causes of these problems can be poor ground conditions combined with poorly executed foundation work. Other factors can also have an effect, such as modern improved insulation material which means, among other things, that thermal insulation of the floor structure is 5-6 times better compared to previously used sawdust/filled floor structures. Furthermore, there are not normally any heat-producing chimneys that extend down into the crawl space.

To take care of moisture and mold problems, many different solutions have been proposed with the aim of improving/or regulating the ventilation of foundation crawl spaces. Attempts have also been made to keep them dry by making the foundations as heated foundations. In this context, the foundations were sealed and thermally insulated, and also ventilated using indoor air or specially heated air from the heated part of the building. Such foundations are relatively expensive, and the technique can be difficult to apply in existing buildings. Since the entire foundation must be ventilated with indoor air, very large air pockets must be handled. An example is described in SE-C-170061. The prior art also includes the installation of separate drying equipment in the crawl space foundation.

There are proposals in which this technique is combined with a method for producing warm floors, see e.g. SE-B-8007770-4. In this case, warm indoor air is directed into an opening between the inner floor and the floor structure insulation before passing down into the insulated foundation to be extracted. This method is difficult to use in existing buildings, and eliminates the need for complete sealing and insulation of the entire crawl space. The necessity to handle very large volumes of heated indoor air will also exist.

Common to many of the methods proposed today to improve the situation of crawl space foundations is the attempt to convert the entire free crawl space into a climate-controlled zone in one way or another. This causes, among other things, the above-mentioned problems of having to handle very large volumes of air. Furthermore, the foundations are usually designed with only static bearing capacity in mind, which means that in many cases the tightness is poor. With the laying of foundation walls made of foundation blocks, the butt joints are often completely unfilled. Complete sealing of the entire crawl space foundation is very difficult and expensive to carry out.

It has previously been proposed to divide the crawl space into different zones. SE-B-7511197-1 describes the use of a perforated air distribution layer. The upper and lower zones therefore communicate with each other via the layer. To push the air down into the lower zone, a higher pressure is used in the upper zone, which also means that air can be pushed back up and into the building. Leaks often occur at pipe bushings and other connections, which makes it virtually impossible to prevent the positive pressure in the foundation from pushing possible bad air from the foundation up into the building. If radon gas is present, this will also be pushed up into the building.

SE-C2-507461 also describes a foundation with a horizontal dividing wall. This partition wall is intended to cause the ventilation air, taken in via outdoor air openings, to flow along the lower surface of the floor structure, to be drawn down into the foundation and discharged to the exterior of the building. For the ventilation described, it is necessary for the entire foundation to be placed under negative pressure, which requires complete sealing of the entire foundation. This is not only expensive, but also very difficult. With outdoor air openings of this type, major problems also arise as a consequence of the positive and negative pressures that the wind pressure causes on the different sides of the building. With the construction described, it is likely that there is positive pressure in the foundation at least some of the time. The fan must still be sized to handle very large amounts of air due to the inevitable leakage in the foundation wall.

Since the known construction uses outside air, this easily leads to condensate being deposited both on the distribution channels and the shielding panel. Even if warm indoor air from the building is used instead of outdoor air, condensate would be applied especially during winter when warm air, which may contain more moisture per volume unit than cold air is drawn into the cold foundation, where the moisture would then be sent out.

The basis for the present invention consists of the knowledge that for successful ventilation of crawl space foundations, it is necessary to limit the volume of the foundation where the ventilation is to be monitored and controlled. This results in smaller amounts of air having to be handled, and sealing of only a limited area becomes necessary, which is relatively easy to achieve compared to sealing an entire crawl space foundation.

According to the present invention, this is achieved by the fact that the crawl space is divided into upper and lower climate zones, which are sealed in relation to each other by means of a tight climate screen. In this connection, the upper climate zone is flowed through by warm indoor air, which keeps this climate zone dry and well ventilated, which prevents the coating of moisture and mould, on e.g. the floor above the crawl space. No regulation of the environment in the lower climate zone is then necessary, as this zone is ventilated in a conventional way using outdoor air holes in the surrounding foundation walls.

The particularly characteristic feature of a method of the type indicated in the first paragraph is, according to the present invention, that the crawl space is part of at least one upper and at least one lower climate zone, that the two climate zones are separated from each other by means of an essentially windproof and vapor-tight climate screen, which forms a tight dividing wall between the climate zones, that the climate screen is arranged at such a height in the crawl space that outdoor air holes in the foundation walls communicate with only the lower climate zone, that the upper climate zone is equipped with at least one supply air opening and at least one outlet air opening, that the supply air opening is connected to a room above the building and that the outlet air opening is connected to an outlet duct, and that a fan is arranged in connection with the outlet duct to maintain a lower pressure in the upper climate zone than the pressure in the room above, so that the the upper climate zone is ventilated with indoor air from the building and the lower climate zone is ventilated with outdoor air.

If this method is used, a dry and well-ventilated space is achieved on the underside of the floor above the crawl space, which eliminates the risk of moisture deposition and mold formation. Since the volume of this space is relatively limited, it can easily be sealed, so that effective negative pressure can be maintained in this zone. This prevents bad air, radon gas etc. is pulled up to the building above. The need for sealing the entire crawl space is also eliminated.

If necessary, the supply air opening can be equipped with a connecting duct to supply dry air from a dryer.

It is preferred that the climate screen is thermally insulated to avoid any significant cooling of the ventilation air that passes through the upper climate zone.

Other characteristics of this method and a device for use in the application of the method appear from the following patent claims. In the following, the invention will be described in more detail with reference to the embodiments shown, and with reference to the accompanying drawings, where Figure 1 shows diagrammatically part of a building foundation of the crawl space type, equipped according to the present invention; figure 2 shows a ground view and an end view of an insulation panel used in a climate screen according to figure 1; figures 3-5 illustrate how the panel according to figure 2 can be assembled; figure 6 shows a mounting rail used in figure 3, shown in plan view and in end view; Figure 6A is a sectional view along the line II-II of Figure 6; figures 7 and 8 show a suspension element, and a wedge in plan view and side view, which are used to hang the mounting rail according to figure 6; figure 9 illustrates the location of an air distribution device used according to the invention; figures 10 and 11 show two embodiments of an air distribution device according to figure 9; figure 12 shows a further embodiment of an air distribution device; figures 13 and 14 show an alternative mounting device for insulation panels in the climate screen; figures 15 and 16 show two further embodiments of mounting devices for insulation panels; figure 17 shows a special embodiment of an insulation panel in plan view and in side view; figure 18 is a mounting element for a panel according to figure 17; figure 19 illustrates several insulation panels according to figure 17 mounted as a climate screen, and figures 20 and 21 illustrate a further embodiment of an insulation panel according to the invention.

In Figure 1, the reference number 1 denotes a load-bearing foundation wall of a building foundation of the crawl space type. The crawl space 2 is also delimited by foundation ground 3 and the insulated floor structure 4 above the crawl space, with an inner floor 5. The reference number 6 denotes one of the insulated outer walls of the building, the reference number 7 relates to the outer panels of the building.

The building receives its supply air via one or more supply air openings 8 in the outer walls, or alternatively from a conventional ventilation system. The crawl space 2 is ventilated via several outdoor air openings 9, suitably arranged with mesh, mounted in the foundation walls 1.

According to the present invention, in order to protect the floor structure 4 above the crawlspace against moisture and microbial growth, the crawlspace 2 is divided into at least one upper climate zone 10 and at least one lower climate zone 11. The climate zones are separated by essentially windproof and vaporproof climate screen 12 which is mounted in essentially parallel to and at a relatively small distance from the underside of the floor structure 4 above the crawl space.

The distance between the climate screen 12 and the floor structure 4 can be as small as 1-2 cm, but is usually 5-6 cm. If it is desired to build in other installations, such as drainage pipes etc., the distance can be 15-20 cm or greater. In all cases, the volume of the upper climate zone 10 is significantly smaller than the volume of the lower climate zone 11.

Since the climate screen 12 protects the floor structure 4 against the conditions in the lower climate zone 11, it is not necessary to take any special precautions regarding the lower climate zone. It can therefore be ventilated in a conventional way using outdoor air openings 9 mounted in the foundation walls 1. This means that the climate screen 12 must always be mounted at a higher level than the air openings 9.

The upper climate zone 10 must be sealed as well as possible against outside air. In this connection, the foundation walls 1 can be sealed over the parts that delimit the climate zone 10 in the lateral direction. Due to the low height of the zone 10, this can be carried out effectively in a simple way, for example by inserting a sealing body 13 which extends on all sides along the foundation walls 1.

In the embodiment shown in Figure 1, the climate screen 12 is constructed of several insulating panels 14 fitted together, which are suitably made of a rigid cellular plastic material, such as e.g. Frigolite. The panels 14 are suspended on pivotable suspension elements 15 which carry mounting rails 16, which will be described in more detail below. The reference number 17 denotes an air distribution device which will also be described in more detail below.

In order to maintain a climate in terms of temperature and humidity in the upper climate zone 10 which prevents moisture deposition and micro-growth on e.g. the underside of the floor structure 4 above the crawl space, the climate zone 10 has a supply opening 18 which is connected to supply end devices 19 via filters 20 in a room above in the building. Two such supply air openings 18 are suitably arranged on each of the two opposite sides of the building, while one or two outlet openings 21, 22 are arranged essentially centrally in the building, and each is connected to an outlet channel 23 and 24.

These can also be combined to form a common channel. If the building is long, an additional supply air opening 18 is arranged every 8 to 10 meters of the length of the building. The outlet openings can consist of extraction pipes which are known per se, with openings distributed along the door. In this connection, the reference numeral 25 denotes a suction fan connected to the ducts 23 and 24, with outlet duct 26 suitably led up over the edge of the building. Supply air can be taken from any desired room in the building.

The fan 25 is adapted to maintain a lower pressure in the upper climate zone 10 than in the room above. This means that warm indoor air will be delivered to the climate zone 10 via the supply openings 18, and will flow along the underside of the floor structure 4 above the crawl space to the outlet opening 21. As a result of the climate screen 12 being insulated, the air passing through the climate zone 10 will not be cooled to any considerable extent during the cold season of the year either, for which reason no moisture deposition will take place. Radiant heat from the floor structure will also contribute to this. In order for the air flow in the climate zone 10 to be distributed over the entire width of this zone, an air distribution device 17 is arranged between the climate screen 12 and the floor structure 4 above the crawl space, which distributes the air flows essentially evenly or in another desired way in the climate zone 10.

The device described above can be used to improve existing foundations, since no precautions are necessary in the building next to the supply air device and extraction fan. Sealing the foundation walls is not critical, since a small amount of outdoor air leaking in can be tolerated due to the small air volumes that have to be handled in this regard. The invention can of course also be used in the production of new buildings. The climate zone 10 can be divided into sections that separate supply and outlet openings for individual climate control if this is desired. The lower climate zone 11 can of course also be divided by additional load-bearing walls or the like without the function being affected.

The climate screen 12 can be varied depending on the needs, and can consist of, next to dense cellular plastic panels, mineral wool panels, e.g. if appropriate with dense lower and upper surface layers. Depending on the outdoor climate, the screen can also be uninsulated and consist of materials under tension. The panels 14 can be suspended from the floor structure 4 as shown, or be supported from below, e.g. if this should prove appropriate.

The supply air openings 18 can also be connected with, next to an optional device 19, an air conditioning system and/or air drying equipment if this is desired. It can also be advantageous, for example in buildings that are unheated in certain parts of the year. Figure 2 shows a circular plastic panel 14 in plan view and from the end. The panel is equipped with a groove 27 which extends on all sides. Figure 2 shows how the grooves 27 are used, when an adjacent panel is joined, to receive one half of a suspension and sealing rail 28 which extends along the entire length or width of a panel. The other half of the rail is inserted into the groove in a nearby panel 14. The rails 28 are equipped with centrally placed, slot-shaped openings through which pivotable suspension elements 15 can be guided down and locked in the desired position.

In order to improve the holding of the rails 28 in the groove 27 in the panels, the rails can be made with longitudinal flanges, which in the event of an attempt to extend a rail out of the groove, are created to perform a reception-like function.

The pivotable suspension elements are used, as can be seen in Figure 4, to hang the panels 14 below the floor structure 4 above the crawl space. In this context, the suspension elements 15 are attached to the floor above the crawl space, and mounting and sealing rails 28 are attached to the suspension elements 15 in the desired position to form a climate zone 10 between the floor structure 4 and the panels 14 with the desired height. Due to the fact that the mounting rails 28 can be fixed at the desired height, the panels 14 can be mounted in the same position regardless of the inclination of the floor structure 4. The use of the mounting rails 28 which are inserted into the grooves 27 in the side edges of the panel 14 also means that small angular variations between the panels can be taken up, see figure 5, without the tightness between the panels being damaged. This can be further facilitated if the rail 28 is equipped with a longitudinal groove 32, see Figure 6, which can function as a hinge. Furthermore, the seal between the panels is not threatened in case of limited movement of these as a result of shrinkage of the panel material or movement in the building. If desired, however, an additional sealing strip 30 can be inserted into the joint between two adjacent panels.

If the panel 14 is adjusted and mounted against the foundation wall 1, a bent mounting rail 31 can be used, see Figure 4. An additional sealing strip 30 can also be inserted here between the edge of the panel and the foundation wall if desired.

Figure 6 shows an assembly and a sealing rail 28 on a larger scale. As can be seen from the end view, the strip is provided with a longitudinal groove 32 which is provided with predetermined breaking points 33, see the sectional view in Figure 6A, to allow material parts 34

to be broken off to form slit-shaped openings in the rail 28. The transverse edges of the openings that have been obtained will in this context be formed by yielding tongues 35. Figure 7 shows a pivotable suspension element 15 seen from the front and from the side. The suspension element 15 is adapted to be fixed in a beam floor with screws or the like, which are passed through a hole 36 at the upper part of the suspension element, which is then angled to a position essentially at right angles to the rest of the suspension element around a hinge axis 37. The width of the suspension element 15 is essentially the same or somewhat greater than the length of the slit-shaped openings in the rail 28, which are formed when the material parts 34 are broken off. At least one edge of the suspension member has teeth, with the result that the yielding tongues 35 in the openings of the rail 28 which hold the suspension member in place in the respective openings and provide resistance to the suspension member are displaced through the opening. On the front side, the suspension element has mutually separate projections 39. Figure 8 shows a thin wedge 40 with a width which essentially corresponds to the width of the suspension element 15. The wedge 40 is adapted to be inserted through an opening in the rail 28 together with the suspension element and on the plane side of the latter, when it has been determined at what height the rail 28 is to be fixed in relation to the suspension element 15. The wedge 40 will then press the suspension element against the longitudinal edge of the slot in the rail, which can then engage between two of the projections 39 to hold the rail 28 firmly in the position taken up on the suspension element 15.

However, the position can be easily adjusted later by pulling the wedge 40 out, moving the rail 28 and inserting the wedge again. The lower part 42 of the wedge 40 is hinged around the shaft 41, which facilitates gripping of the wedge after assembly.

Figure 9 shows how an air diffusion divider 17 is fixed between the floor structure 4 and the climate screen 12 near the inlet opening 18 for the climate zone 10. An embodiment of the air diffusion divider 17 is shown on a larger scale in Figure 10. It is equipped with several openings or slots 29 which will distribute the air flow on desired way across the width of the climate zone. Due to the fact that the divider is bellows-shaped, it can be adapted to the climate zone 10 at different or varying heights. Figure 11 shows an alternative embodiment, in which the divider 17 is perforated with holes 43 and has a lower flange 45 intended to be inserted into the slot in the edge of the insulation panel 14, according to Figure 2, where the upper part of the panel is received in the U-shaped profile 46. The flange 45 will be held pressed into the groove in the insulation panel 4 by means of the connecting and sealing rail 28 (figure 3) which is inserted in the space between the flange 45 and the folded part 47 thereof. Figure 12 shows a further embodiment of an air distribution device. In this case, it consists of two angled profiles 48, 49 which are attached to the gold structure 4 above the crawl space, and respectively the climate screen 12, so that a narrow opening 50 is formed between the profiles 48 and 49. By means of the opening 50, the air flow can through climate zone 10 is made to spread out over the entire width of the zone.

By varying the hole distribution or hole size over the parts according to Figures 10 and 11 in the lateral direction, or by changing the opening width 50 between the angled profiles 48 and 49 in the lateral direction in Figure 12, the desired air distribution in the climate zone can be achieved.

The air diffusion parts according to figures 10, 11 and 12 can also be used to delimit different climatic zones, in which case they are not equipped with openings, and can be mounted in such a way that intermediate openings are not formed.

Figure 13 shows an alternative embodiment of a suspension device for isolating panels that are to form a climate screen 12 according to Figure 1. The device comprises a hanging pivotable suspension element 55 which is connected to a fixing plate 56 via a hinge 37. The fixing plate 56 is intended to be mounted on the underside of the floor structure above the crawl space in the building. The suspension element is equipped with several openings 58 to receive mounting elements 59, by means of which an upper and a lower rail-shaped mounting and sealing profile 60 and 61 can be mounted at the desired mutual distance. This distance is adapted to the insulation panel to be fixed between the profiles.

With the help of this device, the climate screen can thus be constructed of softer insulating panels 62, made of, for example, mineral wool (see figure 14). Foamed plastic strips 63 can then be arranged in the butt joint between the mineral wool panels. Figure 15 illustrates a further alternative suspension device for isolating panels, which is also considered too many panels. It consists of an upper and a lower profiled rail 64 and 65, one of which is provided with an upward flange which can be received in an opening between two downward flanges 67, provided with friction teeth, on the other rail. The rails can thus be locked in relation to each other at the desired mutual distance, which is adapted to the thickness of the insulating panels to be used. Suspension is achieved as before by means of a pivotable suspension element (not shown) which is attached to the upper rail 64. Figure 16 shows a further alternative suspension device comprising upper and lower rails 68, 69 which are connected by means of a longitudinal cellular plastic core 70, the height of which is substantially the same as the thickness of the insulation panels to be used. Suspension for the floor structure is achieved by means of height-adjustable screws which are passed through threaded holes 71 in the cellular plastic core 70. Figure 17 shows a specially shaped insulation panel 72 with milled edge areas 73 along two adjacent edges on one side and along the other two edges on the other side of the panel. The panel has rounded sections 74 at the corners.

Assembly of the panels is carried out by means of reel-like mounting elements 75, see figure 18, which are suspended by means of height-adjustable screws, from the floor structure of the building in positions for the rounded corner parts of the panel 72. Figure 19 shows a section of a climate screen constructed in this way , consisting of panels 72 supported by mounting elements 75, and which form a complete screen set as a result of the overlap between the milled edge areas 73 of adjacent panels. Figures 20 and 21 show specially manufactured insulation panels 76 which are made in such a way that, when mounted on the underside of a floor structure, a defined climate zone is formed between the panels and the floor structure as a result of the panels being designed with spacers 77. These panels are also provided with milled edge areas to overlap each other when assembled according to Figure 20. In this joint, the side flanges 78 can be provided with sealing strips 79. The undersides of the panels are made with recesses 88 corresponding to the spacers 77 to allow volume-efficient stacking of the panels on each other during transport and storage.

When mounting to figure 21, use is also made of special air distribution panels 80 which are made with a longitudinal edge 81, which together with the edge profile 82, delimits a horizontal channel 83 to supply air, and in cooperation with the floor structure above, forms an air distribution opening 84.

It is common to all the mounting systems described above for panels that are to form a climate screen, that the panels can be mounted easily from below on a floor structure above the crawl space. Furthermore, after installation, the panels cannot fall into the lower climatic zone or be pulled up into the upper climatic zone as a result of the negative pressure that prevails there.

The invention is shown by way of example above in connection with some embodiments shown in the drawings. A person skilled in the art will, however, understand that these can be varied in several ways within the scope of the patent claims.

Claims (18)

1. Method for protecting floors above crawl spaces and buildings on crawl space-type foundations from moisture and microbial growth, where the crawl space (2) is bounded by the floor (4) above the buildings' crawl space, load-bearing foundation walls (1) with the air opening (9) for outdoor air and foundation soil (3), characterized in that the crawl space (2) is divided into at least one upper (10) and at least one lower (11) climate zone, in that the two climate zones are separated from each other by means of an essentially windproof and vaporproof climate screen (12 ) which forms a tight dividing wall between the climate zones, the fact that the climate screen (12) is arranged at such a height in the crawl space (2) that the outdoor air openings (9) in the foundation walls (1) communicate with only the lower climate zone (11), in that the the upper climate zone (10) has at least one supply air opening (18) and at least one outlet air opening (21, 22), in that the supply opening (18) is connected to the room above in the building and that the outlet opening (21, 22) is connected to an outlet duct (23) , 24), and that a fan (2 5) is arranged in connection with the outlet channel to maintain a lower pressure in the upper climate zone (10) than the pressure in the room above, so that the upper climate zone (10) is ventilated by indoor air from the building and the lower climate zone (11) is ventilated with outdoor air. 2. Method according to claim 1, characterized in that the supply air opening (18) is equipped with a connected channel which can supply dried air from a drying apparatus. 3. Method according to the preceding claim, characterized in that the part of the foundation wall (1) which delimits the upper climatic zone (10) is sealed, so that a good seal against outdoor air which is drawn into the upper climatic zone is achieved. 4. Method according to the preceding claim, characterized in that a thermally insulated climate screen (12) is used. 5. Method according to the preceding claim, characterized in that the climate screen (12) is placed at such a height that the upper climate zone (10) has a significantly smaller volume than the lower climate zone (11). 6. Method according to the preceding claim, characterized in that the upper climate zone (10) is divided into several sections which are ventilated separately. 7. Method according to the preceding claim, characterized in that the air diffusion device (17) is arranged after the supply opening (18) in the upper climate zone (10). 8. Device for protecting the floor above the crawl space and buildings on foundations of the crawl space type against moisture and microbial growth, where the crawl space (2) is delimited by the floor (4) above the crawl space of the building, supporting foundation walls (1) with the air opening (9) for outside air and foundation ground (3), characterized in that it comprises an essentially windproof and vaporproof climate screen (12), in that the climate screen is arranged in such a way that it divides the crawl space (2) into at least an upper (10) and a lower (11) climatic zone and forms a tight dividing wall between the climatic zones, in that the climatic zones (12) are placed at such a height in the crawl space (2) that the outdoor air openings (9) in the foundation walls (1) communicate with only the lower climatic zone (11), in that the upper climate zone (10) is equipped with at least one supply air opening (18) which is connected to a room above in the building, and an outlet air opening (21, 22) which is connected to an exit duct (23, 24), and that a fan (25 ) is arranged in connection with the outlet channels (23, 24), by means of which it is possible to maintain a lower pressure in the upper climate zone (10) than the pressure in the room above, so that the upper climate zone (10) is ventilated with indoor air from the building and the lower climate zone (11) is ventilated with outside air. 9. Device according to claim 8, characterized in that it comprises an air drying device which can deliver dry air to the air supply opening (18). 10. Device according to claim 8 or 9, characterized in that a gasket (13) is arranged, which seals a part of the foundation wall (1) that delimits the upper climate zone (10) in order to make it difficult for outside air to be drawn into it upper climate zone. 11. Device according to claims 8-10, characterized in that the climate screen (12) is thermally insulated. 12. Device according to claims 8-11, characterized in that the climate screen (12) is placed at such a height that the upper climate zone (10) has a significantly smaller volume than the lower climate zone (11). 13. Device according to claims 8-12, characterized in that the upper climate zone (10) is divided into several sections which have separate supply and output openings. 14. Device according to claims 8-13, characterized in that the air distribution device (17) is arranged after the supply opening (18) in the upper climate zone (10). 15. Device according to claim 14, characterized in that the air distribution device (10) comprises dividers (17) with flow control openings (29, 42) mounted between the floor (4) above the crawl space and the climate screen (12). 16. Device according to claim 15, characterized in that the parts (17) are bellows-shaped in order to be able to be adapted to different heights of the climate zone (10). 17. Device according to claims 8-16, characterized in that the climate screen (12) consists of several panel sections (14) with grooves (27) that extend on all sides, that adjacent panel sections are connected by means of a rail (28) inserted in corresponding tracks in the panel sections (14), and that these rails are suspended on suspension elements (15) that hang down from the floor (4) above the crawl space. 18. Device according to claim 17, characterized in that the rail (28) is made with indications (33) for creating openings in it, that the openings are arranged to be able to receive the suspension elements (15), and that the device comprises a wedge device (40) which can be inserted into the openings to secure the rail (28) at the desired height along the respective suspension elements (15).