WO1998045653A1

WO1998045653A1 - Method and apparatus for extracting moisture and/or mold from a structure of a building

Info

Publication number: WO1998045653A1
Application number: PCT/FI1998/000311
Authority: WO
Inventors: Antero Klemetti
Original assignee: Pohjois-Suomen Kuivausteknikka Oy
Priority date: 1997-04-09
Filing date: 1998-04-08
Publication date: 1998-10-15
Also published as: DK0979378T4; DE69806000T2; NO326062B1; EP0979378A1; FI971482A0; NO994944D0; AU6834698A; EP0979378B2; NO994944L; FI105950B; FI971482L; DE69806000T3; DE69806000D1; EP0979378B1; DK0979378T3

Abstract

Procedure for removing moisture and/or mould from a structure in a building, e.g. from a floor, wall or equivalent, in which procedure air is circulated in the vicinity of the structure to be dried and/or the structure is heated by applying periodic phases of heating and cooling to it. The structure is heated through its essential thickness using an infrared radiator (2) to a raised temperature sufficient to remove moisture and possible mould, and the surface of the structure is cooled via continuous air flushing so that the surface temperature of the structure becomes lower than its inside temperature raised by heating, with the result that the moisture in the warm structure tends to drift towards the cooler surface and is removed from the surface by the air flushing.

Description

METHOD AND APPARATUS FOR EXTRACTING MOISTURE AND/OR MOLD

FROM A STRUCTURE OF A BUILDING

The present invention relates to a procedure as defined in the preamble of claim 1. Moreover, the invention relates to an apparatus as defined in the preamble of claim 15.

Buildings damaged by the effects of moisture and mould are difficult to repair. For successful reparation, it is necessary that the structure af- fected by moisture be thoroughly dried. When a wood, stone or other structure, such as a concrete slab or wall structure gets wet, this will also quickly induce a growth of mould fungi. In conjunction with repairs, any mycocelial filaments in the structure must also be completely eliminated.

In prior art, several methods for drying of structures and elimination of mould are known. In a prior-art procedure, hot air is blown at the structure to be dried or into a space containing the structure. In addition, drying can also be accelerated by circulating the drying air in the space surrounding the structure to be dried. Another prior-art method for the drying of a structure is to use a fixed heating element so connected to the structure to be dried that the structure becomes warm and moisture is evaporated from it as effectively as possible. However, a problem with this method is a relatively long drying time, which further protracts the total repair time of the water damage, thus significantly increasing the costs. A further problem especially in the case of thick objects is that, with prior-art methods, the surface of the structure is heated to a relatively high temperature while the portions deeper inside the structure remain damp. This is because moisture tends to drift towards colder parts, so the hot outer surface of the structure constitutes a barrier to the drying of its deeper portions.

Yet another prior-art method for drying a structure is to apply microwave radiation to the object to be dried. However, microwave radiation is det- rimental to health. When a drier using microwave radiation is used e.g. in an apartment, even the apartment below must be evacuated and also the space being dried must be continuously watched to keep outsiders away. The object of the present invention is to eliminate the drawbacks described above. A specific object of the invention is to present a new type of procedure that allows faster drying of structures than is possible by earlier methods and which makes it pos- sible to effectively combine the use of a heating element and air cooling for the drying of structures after water damage and for the elimination of mould.

A further object of the invention is to present a new apparatus for fast and economical drying of damp structures.

The procedure of the invention is characterised by what is presented in claim 1. The apparatus of the invention for implementing the procedure is characterised by what is presented in claim 15. According to the invention, using infrared radiation, the structure is heated through its essential thickness to a raised temperature that is sufficient to remove moisture and possible mould, and the surface of the structure is cooled by continuous air flushing so that the surface temperature of the structure becomes lower than the inside temperature raised by heating, with the result that the moisture in the warm structure drifts towards the cooler surface and is removed from the surface by the air flushing. Thus, a temperature gradient is created in the structure. The moisture can evaporate from the surface and the mould and spores can be eliminated. The duration of the first heating phase is of the order of a few hours and the duration of the subsequent cooling phase with no infrared radiation applied to the structure is substantially longer and may be even many times as long as the duration of the heating phase. To maintain a sufficient interior temperature, very short heating periods may be additionally used during the cooling phase. The essential point in the invention is the use of infrared radia- tion penetrating deep into the structure and the maintenance of a sufficient inside temperature as well as a somewhat lower surface temperature. Moisture is always removed from inside the structure towards a surface at a lower temperature. The cooler surface can be formed by applying air cooling to that surface of the structure towards which the moisture is to be removed.

The invention has the advantage that the procedure of the invention allows a significant reduction of the time consumed for the drying of structures. In- frared radiation penetrates deep into the structure to be dried, yet without heating the air near the surface because the radiation needs no medium, allowing simultaneous cooling of the surface by air flushing. Moisture can be removed to a desired direction. A further advantage of the invention is that the structure is very effectively dried throughout its thickness. Moreover, the procedure of the invention is not detrimental to health and therefore does not involve any extra health risk to persons working with the appara- tus or to outsiders.

In an embodiment of the procedure, during the heating phase the structure is heated using infrared radiation with a wavelength in the near-infrared range. The wavelength is preferably larger than or equal to 900 nm. Such radiation has a particularly good ability to penetrate into concrete structures.

In an embodiment of the procedure, the infra- red radiation is interrupted periodically and the surface is cooled continuously or periodically. The infrared radiation is preferably interrupted periodically so that the ratio of active radiation time to interrupted time is about 2:4.

In an embodiment of the procedure, the structure is heated to a temperature between 35 - 110°C, and the surface of the structure is cooled by an air flow so that the surface temperature is 3 - 8°C lower than the inside temperature. In view of mould elimination, the temperatures are so selected that the mould filaments and spores are destroyed. It is known that the growth of mould stops and most of the active filaments are destroyed when the temperature is 55 - 60°C. Spores can be destroyed at a temperature of 80 - 100 °C. The filaments of most decay fungi die at temperatures between 35 - 80°C.

In an embodiment of the procedure, the part of the structure to be dried is isolated from the en- vironment so that a negative pressure can be created around it and air is drawn by suction from that area to create a continuous air flow flushing the surface of the structure to remove moisture as well as possible mould. A slight negative pressure continuously maintained creates a suction that effectively removes any moisture drifting to the surface as well as organic residue and spores. The exhaust air is preferably passed out of the building via a filter into the atmosphere. In an embodiment of the procedure, air is blown at the surface of the structure to cool it. After the mould filaments and spores have been removed from the structure by suction, the cooling of the surface of the structure can be enhanced by subjecting the surface to a blast of cold atmospheric air. The air thus blasted is dehumidified using special filters so that the relative humidity of the air is about 10 - 12 %.

In an embodiment of the procedure, during the heating phase the structure is heated using an infrared radiation heater. The wavelength of the thermal radiation emitted by the infrared heater is appropriate for creating a heat that penetrates deep into the structure.

In an embodiment of the procedure, the heating, air suction and/or air blasting are activated and interrupted in accordance with a predetermined precept.

In an embodiment of the procedure, the temperature of the structure being dried, its humidity and/or other corresponding quantities essential to moisture and mould removal are monitored and, based on this monitoring, the heating and air blasting/suction are regulated. Moreover, the flow rate, temperature and humidity of the air being blown and/or sucked can be monitored. Based on measured quantities, reports can be printed out. A report may contain essential information regarding the progress of moisture and mould removal, such as temperature of the structure, air humidity, air temperature, process duration and/or other quantities to be defined. According to the invention, in the apparatus for implementing the procedure of the invention, the heating element is a planar infrared radiator provided with a central through opening; and the apparatus comprises a controller arranged to control the operation of the heating element and the means for creating an air flow inside the casing in accordance with a predetermined precept. In its simplest form, the controller is e.g. a timer which switches electric power to the heating element on and off. The central opening in the infrared radiator is of essential importance to uniform cooling of the surface of the structure. Without a central opening in the radiator, cooling air will not flow to the central part of the planar infrared radiator, so the structure in the central part will be overheated. For instance, when a concrete slab with a thermal insulation of cellular plastic (Styrox) under it is being dried, the heat will easily burn through the insulation in the central area of the IR radiator if the surface cooling of the concrete slab is not functioning in that area.

In an embodiment of the apparatus, the wave- length of the infrared radiation emitted by the infrared radiator is in the near-infrared range.

In an embodiment of the apparatus, the wavelength of the infrared radiation emitted by the infrared radiator is longer than or equal to 900 nm, pref- erably about 900 - 3000 nm.

In an embodiment of the apparatus, the controller has been arranged to interrupt the infrared radiation periodically and to control a fan so as to make it work continuously or periodically. In an embodiment of the apparatus, the controller has been arranged to interrupt the infrared radiation periodically so that the ratio of active radiation time to interrupted time is about 2:4.

In an embodiment of the apparatus, the means for creating a negative and/or positive pressure comprise an air duct opening to the inside of the casing and a fan disposed in the air duct to create suction and/or blowing.

In an embodiment of the apparatus, the appa- ratus comprises a first humidity sensor disposed inside the casing near the structure to be dried for the determination of humidity in the vicinity of the structure and for supplying the controller with a signal corresponding to the humidity. In an embodiment of the apparatus, the apparatus comprises a second humidity sensor, which is disposed in the air duct for determining the humidity of the air flowing in it and for supplying the controller with a signal corresponding to the humidity.

In an embodiment of the apparatus, the apparatus comprises a first temperature sensor, which is disposed inside the casing in the vicinity of the structure to be dried for determining the temperature near the structure and supplying the controller with a signal corresponding to that temperature.

In an embodiment of the apparatus, the appa- ratus comprises a second temperature sensor, which is disposed in the air duct for determining the temperature of the drying air flowing in it and supplying the controller with a signal corresponding to that temperature. Using the apparatus of the invention, it is also possible to implement a drying system that could be used e.g. in conjunction with the reparation of major water damage. The system can be implemented e.g. by connecting a necessary number of drying apparatus as provided by the invention to a common central control unit, which may be a computer or equivalent. In this case, the number of apparatus needed could be determined e.g. by the number of rooms or equivalent. Further, a computer in the system could collect humid- ity, temperature and flow data from the control means of each apparatus, analyse the data and control the temperature and flow rate in each apparatus individually, taking the overall situation regarding drying of the object into account. Moreover, the system may com- prise an output device connected to the computer to allow the printing of reports relating to the drying, temperatures and humidity in different parts of the object, etc. Thus it is also possible to use different drying programmes found to be effective for different objects by simply providing the computer with a new programme.

In the following, the invention will be de- scribed by referring to the attached drawing, in which Fig. 1 presents an embodiment of the apparatus of the invention in lateral longitudinal cross- section, Fig. 2 presents another embodiment of the apparatus of the invention in perspective view,

Fig. 3 presents section III-III of Fig. 2, Fig. 4 presents the infrared radiation of the apparatus in Fig. 2 as seen from below, and Fig. 5 presents a section through an example structure dried using the procedure and apparatus of the invention.

Fig. 1 illustrates the principle of an apparatus for removing moisture and mould from a struc- ture, such as a floor, wall or equivalent. In this figure, the apparatus is placed on a wet concrete bottom slab B having a thickness of e.g. 70 mm. Under the concrete slab there is an insulating layer with a plastic foil under it and sand under the foil. The ap- paratus comprises a casing 1, which is a box with one side open and which is used to isolate an area of the structure to be dried from the environment so that a negative pressure can be created in that area. The open side of the casing box 1 is placed against the structure to be dried. Mounted in the hollow space inside the casing 1 is an infrared heater panel 2, which emits heating radiation to the structure to be dried. The apparatus is provided with means 3, 4 for creating a negative and/or positive pressure inside the casing 1 to produce an air flow inside the casing. The casing 1 can be so set against the structure that a slight negative pressure can be generated inside the casing. Between the edge of the casing 1 and the surface of the structure B there is a narrow gap 10 about 5 - 15 mm wide, through which cool air can flow into the casing during suction so that this air flow continuously flushes the surface of the structure to be dried. Fur- thermore, the apparatus comprises a controller 5, which has been arranged to control the operation of the heater element 2 and the means 3 for creating an air flow inside the casing in accordance with a prede- termined precept. The means for creating a negative and/or positive pressure consist of an air duct 3 which opens inside the casing, and a fan 4 disposed in the air duct 3 to produce suction and/or blowing.

Using the procedure of the invention, a 70 mm thick wet concrete slab as shown in Fig. 1 can be dried in 3 - 7 days. The structure is subjected to periodic infrared radiation from an IR radiation heater 2 by first heating the structure continuously for a given period so that it reaches a temperature of 60 - 75 °C. At the same time, the surface of the structure is cooled by a continuous or periodic weak suction air flow, which is produced by means of the fan 4, whose suction side is connected to the air duct. After the inside temperature of the structure has risen to a suitable level sufficient for removing moisture and possible mould, the heating is interrupted for a substantially long period of time while suction is carried on to draw air from inside the casing, i.e. a negative pressure is maintained throughout this cool- ing phase. In this way, the temperature of the cooled surface of the structure becomes somewhat lower, e.g. about 3 - 8 °C lower than the temperature inside the structure raised by heating. Therefore, the moisture in the warm structure tends to drift towards the cooler surface, from where it effectively evaporates into the suction air due to the slight negative pressure. After the structure has been dried, its temperature can be raised for a short period of time to 100 - 110 °C to eliminate mould and spores from the surface of the structure and from the structure itself. After the elimination of mould and mould spores, the cooling of the surface can be further enhanced by blowing dry air at he surface of the structure.

By means of the controller 5, the suction and/or blowing of air is activated and interrupted in accordance with a predetermined precept provided in the controller 5.

The apparatus additionally comprises a first humidity sensor 6 disposed in the space inside the casing 1 near the structure to be dried to determine the moisture content in the vicinity of the structure and to give a signal corresponding to the humidity to the controller 5. A second humidity sensor 7 is placed in the air duct 3 to determine the moisture content of the air flowing in it and to give a signal corresponding to the moisture content to the controller 5. A first temperature sensor 8 is disposed in the space inside the casing near the structure to be dried to determine the temperature in the vicinity of the structure and to give a signal corresponding to that temperature to the controller 5. A second temperature sensor 9 is disposed in the air duct 3 to determine the temperature of the drying air flowing in it and to give a signal corresponding to this temperature to the controller 5. By means of the sensors, the temperature of the structure being dried, the humidity and/or other corresponding quantities essential in respect of removal of moisture and mould are monitored, and, based on this monitoring, the heating and suction/blowing of air are controlled. Other quantities that may be monitored are the flow rate, temperature and moisture content of the air being blown and/or sucked. The results can be printed out as a report giving essential information about the progress of the moisture and mould removal process, such as the temperature of the structure, air humidity, air tempera- ture, process duration and/or other quantities to be determined.

Fig. 2 shows a perspective view of an appara- tus corresponding to the one in Fig. 1. It can be seen from the figure that the casing 1 is a box-like case with four side walls 12 and a top wall 13, inside which an infrared radiator 2 as illustrated by Fig. 4 is suspended. The casing 1 in the example has a length of 1250 mm, a width of 650 mm and a height of 80 mm. As is shown in the sectioned view in Fig. 3, the casing has screwed legs 14 supporting it on a base, so that the gap 10 between the side walls 12 and the base can be adjusted as desired by turning the legs. As is further visible from the sectioned view in Fig. 3, the top wall 13 has in the middle of it a collared hole 15 forming an air duct. Mounted over the hole 15 is an aggregate consisting of a fan mechanism 4 and a con- troller 5, comprising a fan motor, a fault current protector and timers for the infrared radiator and the fan motor. The hole in the top wall 13 is aligned with the central hole 11 in the infrared radiator 2 shown in Fig. 3 and 4. Fig. 4 shows a through hole 11 in the infrared radiator panel 2, which ensures that the air flow will uniformly flush the surface of the structure to be dried over the whole area under the infrared radiator 2. The resistance wire pattern 16 has been adapted to the hole 11. The length of resistance wire on the panel is about 100 metres. The IR radiator has been fitted to emit infrared radiation at a given wavelength. In a preferred case, infrared radiation in the near-infrared range is used, which has a good ability to penetrate into wet structures. The wavelength may be e.g. about 1000 nm.

In the examples in Fig. 1 and 3, the moisture is mainly removed via that surface which is cooled by air flushing and from whose direction the heating is applied. In the example in Fig. 3, the structure to be dried consists of a 70 mm thick concrete slab, with a 70 mm expanded polystyrene insulation under the slab and sand under the insulation. Such a structure could be dried in 5 weeks (35 days) by an air drying technique or in 0.5 weeks by using infrared radiation. By the method of the invention, a structure like this was dried in 3.5 days from an initial relative humidity value of 93% to a final humidity value of 60%. During infrared heating, the top surface of the concrete slab is at temperature a few degrees higher than the temperature inside the structure. When IR heating is switched off and air cooling is continuously active, the temperature of the top surface of the concrete slab becomes considerably lower than the temperature inside the structure. The difference may be as large as 50 °C. Heating and cooling periods are repeated un- til the structure is dry.

Fig. 5 shows an example of another type of structure, which was dried by the method of the invention. Topmost in the structure is a concrete surface slab 17, under which there is a layer of expanded polystyrene 18 at the edges under the exterior walls. Under the insulation there is a 0.5 m thick layer of sand filling 19. Under the sand filling 19 there is a lower counter-slab 20, below which there was a bomb shelter space. The structure to be dried is at ground surface level. The sand filling 19 was very wet, with a relative humidity as high as about 95%, because water had been left in the sand filling during construction. The surface slab 17 had a relative humidity of about 80 -90%. In this case, no microwave radiator could be used because the bomb shelter 21 was in continuous use as a storage room for a pharmacopoeia for a hospital building. Instead, the structure was heated with an infrared radiator from the top side of the surface slab 17, but with the difference from the pre- vious examples that in this case the cooling was performed using air blasting from the top side instead of suction. In addition, a negative pressure was gener- ated in the bomb shelter space 21 below the structure. In this way, the moisture was driven downward and removed via holes in the counter-slab. The amount of water removed from the structure was 15 tons and the fi- nal humidity achieved was 60%, which means that the structure was completely dried.

The invention is not restricted to the examples of its embodiments described above, but many variations are possible within the scope of the inven- tive idea defined by the claims.

Claims

1. Procedure for removing moisture and/or mould from a structure in a building, e.g. from a floor, wall or equivalent, in which procedure air is circulated in the vicinity of the structure to be dried and/or the structure is heated by applying periodic heating and cooling phases to it, characterised in that, using infrared radiation, the structure is heated through its essential thickness to a raised temperature that is sufficient for removing moisture and possible mould, and the surface of the structure is cooled via air flushing so that the surface temperature of the structure becomes lower than its inside temperature raised by heating, with the re- suit that the moisture in the warm structure tends to drift towards the cooler surface and is removed from the surface by the air flushing.

2. Procedure as defined in claim 1, characterised in that during the heating phase the structure is heated using infrared radiation with a wavelength in the near-infrared range.

3. Procedure as defined in claim 1 or 2, characteri sed in that the wavelength of the infrared radiator is 900 nm or more.

4. Procedure as defined in any one of claims

1 - 3, characterised in that the infrared radiation is interrupted periodically and the surface is cooled continuously or periodically.

5. Procedure as defined in any one of claims 1 - 4, characterised in that the infrared radiation is interrupted periodically so that the ratio of active radiation time to interrupted time is about 2:4.

6. Procedure as defined in any one of claims 1 - 5, characterised in that the structure is heated to a temperature between 35 - 110┬░C.

7. Procedure as defined in any one of claims 1 - 6, characterised in that the surface of the structure is cooled by an air flow so that the surface temperature is 3 - 8┬░C lower than the inside temperature.

8. Procedure as defined in any one of claims 1 - 4, characterised in that the structural part to be dried is isolated from the environment so that a negative pressure can be created in that area, and air is continuously drawn by suction from said area to create an air flow flushing the surface of the structure and to remove moisture as well as possible mould.

9. Procedure as defined in any one of claims 1 - 8, characterised in that dry air is blown at the surface of the structure.

10. Procedure as defined in any one of claims 1 - 9, characterised in that the heating, air suction and/or air blasting are activated and in- terrupted in accordance with a predetermined precept.

11. Procedure as defined in any one of claims 1 - 10, characterised in that the air to be blasted is dehumidified.

12. Procedure as defined in any one of claims 1 - 11, cha r a ct e r i s e d in that the temperature, humidity and/or other corresponding quantities essential to moisture and mould removal are monitored and, based on this monitoring, the heating and air blasting/suction are regulated.

13. Procedure as defined in any one of claims

1 - 12, ch a r a ct e r i s ed in that the flow rate, temperature and moisture content of the air being blasted and/or sucked are monitored.

14. Procedure as defined in any one of claims 1 - 13, cha ra cte r i s ed in that a report containing essential information regarding the progress of moisture and mould removal, such as temperature of the structure, air humidity, air temperature, process duration and/or other quantities to be defined, is printed out.

15. Apparatus for implementing a procedure as defined in any one of claims 1 - 14 for the removal of moisture and/or mould from a structure, such as a floor, wall or equivalent, said apparatus comprising a box-like casing (1) , which is open on one side to be placed against the structure to be dried, and a heat- ing element (2) mounted in the space inside the casing, and means (3, 4) for generating a negative and/or positive pressure to create an air flow inside the casing, characteri s ed in that the heater element (2) is a planar infrared radiator provided with a central through opening (11); and that the apparatus comprises a controller (5) arranged to control the operation of the heating element (2) and the means

(3) for creating an air flow inside the casing in accordance with a predetermined precept.

16. Apparatus as defined in claim 15, character i s ed in that the means for generating a negative and/or positive pressure comprise an air duct (3) that opens inside the casing, and a fan

(4) for producing suction and/or blast in the air duct.

17. Apparatus as defined in claim 15 or 16, charact eri s ed in that the wavelength of the infrared radiation emitted by the infrared radiator (2) is in the near-infrared range.

18. Apparatus as defined in any one of claims

15 - 17, characteri sed in that the wavelength of the infrared radiation emitted by the infrared radiator (2) is 900 nm or more.

19. Apparatus as defined in any one of claims 15 - 18, cha racter i s ed in that the controller (5) has been arranged to interrupt the infrared radiation periodically and to control the fan (4) so as to make it work continuously or periodically.

20. Apparatus as defined in any one of claims 15 - 19, characterised in that the controller (5) has been arranged to interrupt the infrared radiation periodically so that the ratio of active radiation time to interrupted time is about 2:4.

21. Apparatus as defined in any one of claims 15 - 20, characterised in that the controller (5) has been arranged to control one or more appa- ratus.

22. Apparatus as defined in any one of claims 15 - 21, characterised in that it comprises a first humidity sensor (6), which is disposed inside the casing (1) near the structure to be dried to de- termine the moisture content in the vicinity of the structure and to supply the controller (5) with a signal corresponding to the moisture content.

23. Apparatus as defined in any one of claims 15 - 22, characterised in that it comprises a second humidity sensor (7), which is disposed in the air duct (3) to determine the moisture content of the air flowing in it and to supply the controller (5) with a signal corresponding to the moisture content.

24. Apparatus as defined in any one of claims 15 - 23, characterised in that it comprises a first temperature sensor (8), which is disposed inside the casing in the vicinity of the structure to be dried to determine the temperature near the structure and to supply the controller (5) with a signal corre- sponding to that temperature.

25. Apparatus as defined in any one of claims 15 - 24, characterised in that it comprises a second temperature sensor (9), which is disposed in the air duct (3) to determine the temperature of the drying air flowing in it and to supply the controller (5) with a signal corresponding to that temperature.