EP2947396B1 - Method for ventilating a room and ventilation system for same - Google Patents

Description

I. Field of application

The invention relates to the ventilation of particular cool rooms such as cellars or garages in which precipitates due to excessive humidity condensation on the walls.

At the beginning, the masonry will absorb this moisture, but from a certain saturation of the masonry with absorbed moisture, this will lead to mold on the insides of the walls of the room.

II. Technical background

This has already been tried by conventional ventilation to avoid, so either by the windows of this room were at least slightly open to a high proportion of time or by regular breather, with the aim of the humid air to flow out of the room to the outside and / or to let in dry air from outside.

For this purpose, with manual ventilation, the windows have been opened by feeling, so if you had the feeling that the air outside is drier than inside, which was subjectively often decided on the outside prevailing temperature:
So it was usually aired when the outside temperature was higher than in the room and in winter usually not at all, so as not to cool the room any further.

The disadvantage of this method is, on the one hand, that one had to actively open the windows manually, if one had this impression, and that even then due to the open windows alone, the air flow and exchange from inside to outside was relatively low due to lack of active generation of an air flow and thus also the incoming effect.

In addition, a higher outdoor temperature than the indoor temperature does not always mean that the air outside is drier than inside the room to be ventilated.

Therefore, methods have been developed in which, in addition to the outside and inside temperatures, further measured values are taken into account in order to determine a suitable ventilation period.

When in the DE 10 2008 044 439 A1 described control device and the associated method for automatic ventilation of basements, the respective temperatures and relative humidity are determined by means of an outdoor temperature sensor and an indoor temperature sensor and the measured values to a control device via USB, RJ45, Ethernet, Bluetooth, NFC, WLAN and / or GPRS / UMTS so that it can calculate the dew point and, based on the comparison of the calculated outside dew point with the measured internal temperature or a change in the relative indoor humidity, initiates or terminates ventilation.

The DE 10 2008 044 439 A1 discloses a method according to the preamble of claims 1 and 2 and a ventilation system according to the preamble of claim 8.

A mainly intended for use in a roof truss ventilation is from the WO 2007/139507 A1 known. The ventilation takes place by means of an outside air in the interior of the advancing blower and a flap through which the internal air can escape. Inside and outside the too ventilating room by means of appropriate sensors, the relative humidity, the temperature and possibly the (partial) water vapor pressure, passed to a computing unit and processed by this effect that either i) the ventilation is started when within the room to be ventilated, the water vapor pressure higher is turned off or the ventilation is switched off if, within the room to be ventilated, the water vapor pressure is lower than outside or ii) the operating condition results from a value X calculated by means of an algorithm dependent on the relative humidity and the temperature.

Another way in which a temperature and humidity dependent ventilation method can be controlled is in the DE 199 52 519 A1 shown. If the relative humidity inside the room to be ventilated exceeds a predefined value, it is decided on the basis of the partial pressure difference inside and outside the room to be ventilated whether the fan is switched on or off. In the opposite case, ie if the predefined value is not exceeded, the fan is switched on when the dew point temperature of the air inside the room to be ventilated is greater than the surface temperature at the outer wall edge, measured inside the room, or switched off, if this is not the case Case is. The measurement data required for this purpose are determined by temperature and humidity sensors and fed to a controller so that the partial vapor and saturation pressures as well as the dew point temperature can be calculated therefrom.

Another method and apparatus for dehumidifying buildings by removing the liquid forming directly from the basement floor before it spreads to other areas of the building is in the DE 44 12 251 A1 describe. The periodically operated blower for air exchange draws the basement or the basement air rooms with a relative to the outside air higher relative humidity and higher temperature, which then by air with lower humidity and lower Temperature, which enters through leaks from the outside, is replaced. If there is a risk of frost, the fan will not be switched on.

In the DE 10 2010 055 065 A1 It is shown how a room, without providing a breakthrough for a blower or fan, regulated outside air supplied and existing air in the room can be dissipated. For this purpose, a window which is already present in most rooms is opened in a controlled manner and, if necessary, a ventilator located in the room is additionally started. Depending on the humidity of the wall, indoor air humidity and outdoor humidity, a control unit starts, reduces, increases or terminates the ventilation of the basement room.

Moreover, from the DE 10 2011 108 021 A1 a control of a dry room ventilator is known which monitors that there can be no dew point undershot within the drying room at any time. For this purpose, the fan is switched off when a corresponding parameter, selected from the outside and inside temperature, humidity inside and outside and the internal wall temperature, the dew point below the basement wall approaches.

The absolute humidity, which expresses the amount of water dissolved in grams in a volume fraction of air, can not be measured directly, or measured only with great effort.

The humid air perceived by humans is the relative humidity, which can amount to a maximum of 100 %, which corresponds to a saturation of the air with steam. A maximum saturation of the air with moisture, ie water vapor, thus a relative humidity of 100 %, is at any temperature and at an associated air pressure - more precisely: associated partial pressure of the water - or vice versa for a given air pressure - associated partial pressure of the water - at a certain temperature. In a pT diagram, this can be done as a so-called dew point curve according to FIG. 2 a represent.

As a rule, the air temperature T _Li inside and outside T _{La are known} from the current state _.

However, with conventional methods, only the relative humidity FL _rel can be measured directly or by measuring the prevailing pressure and temperature as shown in the diagram in Fig. 2a determine.

For this current state (x), the dew point, which is at the same pressure level, can be read on the dew point curve, as well as the dew point temperature T _T.

III. Presentation of the invention a) Technical task

It is therefore the object of the invention to provide a method for ventilating a room with too humid air for the purpose of reducing the humidity in the room, which can be carried out reliably and with little effort, and to provide a ventilation system for this purpose ,

b) Solution of the task

This object is achieved by a method having the features of claim 2 or by a ventilation system having the features of claim 8. Advantageous embodiments will be apparent from the dependent claims.

The introduction of outside air into the room, whose internal air is to be reduced in terms of moisture contained, makes sense only if the absolute humidity, ie the amount of water contained in one cubic meter of air, is lower in the outdoor air than in the indoor air.

Only then is the ventilation of the moisture content of the indoor air reduced, which is the primary goal, not least to deliver already stored in the masonry moisture from the wall back to the air of the interior and thereby long-term to dry the masonry again.

To achieve this, the method can be used to permanently or at short intervals by means of appropriate sensors to determine the absolute humidity in the room and outside the room, so the outside air, and automatically by activating the at least one fan outside air in the To transport space only when the absolute humidity of the outside air is lower than that of the indoor air, preferably by a predetermined absolute humidity difference. Because if this difference is too small, the effect of reducing the absolute humidity in the room is so low that the energy required for the fan is not worthwhile.

Since the determination of the absolute humidity from the data usually available, namely air temperature and relative humidity of the air, can not be determined with great effort or without knowledge of the water vapor partial pressure, according to the invention is preferably for the decision whether to be aired should or not, instead of the absolute humidity inside and outside of the room, the dew point temperature inside and outside the room used:
The supply and discharge of outside air, so the ventilation, takes place only when the dew point temperature of the outside air is lower than the dew point temperature of the indoor air.

According to the invention, there is a certain minimum distance between the two dew-point temperatures, namely a freely selectable dew-point temperature difference, because if the distance between the two dew-point temperatures is too short, the effect would be to reduce the moisture the indoor air is so low that this does not pay for the energy required for the fan.

For the determination of the dew point temperature inside and outside the room is technically much easier than the determination of the respective absolute humidities, and in most cases, when the absolute humidity outside is lower than inside the room, the corresponding dew point -Temperature outside lower than inside.

In a few exceptional situations, such as when outside the room there is a very humid, humid air at high temperature, such as just before a thunderstorm, this synchronicity is broken, and then control of aeration could be dependent on the relation of dew point temperatures lead to a faulty control.

However, as these exceptional cases are very rare, the overall result of the ventilation is only slightly reduced and can be accepted because of the advantage of much simpler control.

If you want to prevent in any case, that even in some cases humid outside air, ie with a higher absolute humidity outside of the room, flows into the room, so instead of or in addition the absolute humidity inside and outside the room must be determined and compared with each other and only be ventilated outside the room of lower absolute humidity than in the room.

Normally, in addition to temperature and relative humidity, it is also necessary to determine the current air pressure.

However, since in the generally prevailing temperature range of - 20 ° C to + 40 ° C, the actual air pressure on the result of the absolute humidity plays only a minor role, the actual air pressure replaced by the present at the respective sea level of the site average air pressure and given the control, preferably even independent of the respective sea level for this purpose, the standard air pressure stored in the controller.

Even if controlled according to this parameter, there should be at least an absolute absolute humidity difference between the absolute outside air humidity and the inside air humidity in order to make ventilation more efficient.

When ventilation is in progress, it is ended when the dew point temperature difference and / or the absolute humidity difference falls below the respective predetermined minimum difference.

According to the invention, the dew point temperature difference and / or the absolute humidity difference can be selected and set.

In order to avoid overcooling the room below a predetermined minimum temperature, ventilation can only be provided if the air temperature in the room is above this minimum set temperature, and the ventilation stops when the temperature in the room has dropped to this predetermined minimum temperature.

In the same way, a maximum temperature can be selected as the air temperature inside the room.

The vent may preferably be performed at intervals, preferably wherein the ventilation intervals are not longer than the pause intervals, preferably only one fifth as long, more preferably only 1 / 10th as long, more preferably only 1 / 20th as long as the pause intervals.

The temperature sensor and / or the moisture sensor both on the outside and / or on the inside is activated for the measurement at most every 1000 milliseconds. In this case, the distance between the activated phases, that is to say the measurements, and thus also the ratio of durations of deactivity to activity of these sensors, is increased the lower the measured temperature is.

wobei
- bei einem 12 Bit Prozessor: C1 =-2.0468 ; C2 = 0,0367 ; C3 = -1,5955 x e^-6
- bei einem 8 Bit Prozessor: C1 = 2.0468 ; C2 =0.5872 ; C3 =.-4,0845 x e^-4 Preferably, the measured relative air humidity prior to further processing, in particular for calculating the absolute humidity, linearized to LF ' _rel according to the formula $$\mathbf{LF}{\text{'}}_{\mathbf{rel}}={\mathbf{C}}_1+{\mathbf{<figure-callout\; id="2"\; label="C"\; filenames="imgf0001.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\times {\mathbf{LF}}_{\mathit{rel}}+{\mathbf{<figure-callout\; id="3"\; label="C"\; filenames="imgf0001.png"\; state="\{\{state\}\}">C</figure-callout>}}_3\times {\mathbf{<figure-callout\; id="2"\; label="LF\; rel"\; filenames="imgf0001.png"\; state="\{\{state\}\}">LF\; </figure-callout>}}_{\mathbf{rel}}{}^2\mathrm{}\left(\%\mathrm{}{\mathbf{LF}}_{\mathit{rel}}\right)$$

in which
- with a 12- bit processor: C 1 = - 2.0468 ; C 2 = 0.0367 ; C 3 = - 1.5955 xe ^-6
- with an 8- bit processor: C 1 = 2.0468 ; C 2 = 0.5872 ; C 3 = .- 4.0845 xe ^-4

wobei T1 und T2

• bei einem 12 Bit-Prozessor T1 = 0,01 und T2 = 0,00008 betragen und
• bei einem 8 Bit-Prozessor T1 = 0,01 und T2 = 0,00128 betragen.

Preferably, then, the linearized relative humidity is in deviation of the temperature at the sensor of 25 ° C in a true relative humidity LF " _rel converted according to the formula $$\mathbf{LF}{"}_{\mathbf{rel}}=\left({\mathbf{t}}_{°\mathbf{C}}-\mathrm{25}\right)\times \left(\mathbf{T}1+\mathbf{<figure-callout\; id="2"\; label="T"\; filenames="imgf0001.png"\; state="\{\{state\}\}">T</figure-callout>}2\times {\mathbf{LF}}_{\mathit{rel}}\right)+\mathbf{LF}{\text{'}}_{\mathbf{rel}}.$$

where T 1 and T 2

• for a 12- bit processor T 1 = 0.01 and T 2 = 0.00008 and
• for an 8- bit processor, T 1 = 0.01 and T 2 = 0.00128 .

wobei Zustand t _Bereich (°C) α (hPa) β λ (°C) Über Wasser -45 - 60 6.112 17.62 243.12 Über Eis -80 - 0.01 6.112 22.46 272.62 The absolute humidity is determined from the relative humidity and the temperature, in particular on the basis of a fixed predetermined, in particular average, air pressure according to the formula $$L{F}_{\mathit{Section},}=\mathrm{216},7\times \frac{\frac{L{F}_{\mathit{rel}}}{\mathrm{100}\%}\times \alpha \times \exp \left(\frac{\beta \times t\left(°C\right)}{\lambda +t\left(°\mathrm{<figure-callout\; id="15"\; label="C"\; filenames="imgf0004.png"\; state="\{\{state\}\}">C</figure-callout>}\right)}\right)}{\left(\mathrm{273},\mathrm{15}°C+t\left(°C\right)\right)}.$$

in which Status t _range (° C) α (hPa) β λ (° C) About water -45 - 60 6112 17.62 243.12 Over ice -80 - 0.01 6112 22:46 272.62

wobei T-Bereich T_n (°C) m Über Wasser, 0-50°C 243-12 17,62 Über Eis, -40-0°C 274,62 22,46 If the dew point temperatures are used for the control, the respective dew point temperature is determined according to the formula: $$T_T\left(L{F}_{\mathit{rel},}.T\left(°K\right)\right)=T_n\times \frac{\mathit{In}\left(\frac{L{F}_{\mathit{rel},}}{\mathrm{100}\%}\right)+\frac{m\times T\left(°K\right)}{T_n+T\left(°K\right)}}{m-\mathit{In}\left(\frac{L{F}_{\mathit{rel},}}{\mathrm{100}\%}\right)-\frac{m\times T\left(°K\right)}{T_n+T\left(°K\right)}}$$

in which T area T _n (° C) m Over water, 0-50 ° C 243-12 17.62 Over ice, - 40-0 ° C 274.62 22.46

A corresponding ventilation system for ventilating a room according to the invention comprises the features of claim 8.

In order for the sensors and / or the controller to be able to determine at least the dew point temperature inside and outside the room, ie at the inner sensor and the outer sensor, the two sensors can either measure the relative humidity and the temperature or directly measure the absolute humidity, from which the controller, or a processor eg in the respective sensor, the absolute humidity is calculated. As the air pressure is then a predetermined, for this height, on which the ventilation system operates, mean air pressure, or independently of the sea level known standard air pressure entered into the controller, except indoor sensor and outdoor sensor are also able to measure the current air pressure , Then the latter is used.

The absolute humidity is determined from temperature and relative humidity according to the known contexts, see in particular FIG. 3 ,

Calculated by the controller determines the absolute humidity from the relative humidity and temperature, in particular on the basis of a fixed predetermined, in particular average, air pressure according to the formulas given above.

If dew point temperatures are used for the control, the respective dew point temperature is also determined according to the formula explained in the procedure.

The controller preferably has a display which separately displays the dew point temperatures and / or the absolute humidity for the inner sensor and the outer sensor.

In addition, the dew point temperature difference and / or the absolute humidity difference between inside and outside can be displayed.

In addition, the display can in particular also display the current temperature in the room and outside the room, as measured at the respective sensors.

The two sensors and / or the at least one fan are signal-technically connected by cable or wirelessly, in particular by radio.

If the ventilation system comprises a second fan, so that one fan transports outside air into the room and the other fan discharges inside air to the outside, the two fans are preferably located opposite each other in the room, with a maximum possible distance to each other to flow through its entirety as well as possible.

If the system comprises only one fan, in addition - preferably again at a point as far as possible from the one fan of the room - another air opening is necessary, which is only open when it is ventilated. It thus has a closure element, which is only when activating the fan, preferably active, opened, for example in the form of a flap.

The one or the existing two fans also have flaps that close the air passage opening as tight as possible with the fan off, and are open only when the fan is running.

The controller usually contains a relay. Preferably, the controller also includes a test function for this relay to always be able to determine whether the relay is working properly, which is crucial for the overall function of the controller.

The controller may preferably include a program for continuous ventilation in which ventilation is continuous, provided that the prerequisite is met, ie dew point temperature outside <as dew point temperature in the room to be ventilated or / and absolute humidity outside <as absolute humidity in the ventilated Room.

The controller may also preferably include a refrigeration program in which the temperature in the room may be lowered by supplying colder outside air. The supply of outside air can be continued as long as either the relative humidity in the room and / or the absolute humidity in the room does not exceed a corresponding predetermined maximum limit, ie maximum predetermined relative humidity or maximum predetermined absolute humidity, if not previously the desired target temperature is reached.

If dew point control is used, outside air supply continues as long as the dew point temperature is lower than the inside dew point temperature.

The controller may also include a heating program in which the temperature in the room can be increased by supplying warmer outside air. The supply of outside air can be continued until the relative humidity in the room does not rise above a predetermined maximum relative humidity in the room and / or the absolute humidity in the room Room does not rise above a predetermined maximum absolute humidity in the room and / or the dew point temperature in the room does not fall below the dew point temperature outside the room, unless the desired target temperature has already been reached.

Preferably, the moisture sensor is a capacitive sensor, as they measure very accurately and are durable.

For the same reason, the temperature sensor is preferably a bend-gap sensor.

The ventilation system is preferably constructed so that no significant temperature line from the controller, in particular from its processor, to the sensor, in particular the humidity sensor takes place.

c) embodiments

Fig. 1:

eine Belüftungssituation,

Fig. 2a, b:

den Taupunkt in Abhängigkeit vom Wasserdampf-Partialdruck und der Lufttemperatur,

Fig. 3:

die Taupunkt-Temperatur in Abhängigkeit von der Lufttemperatur und der relativen Luftfeuchtigkeit

Embodiments according to the invention are described in more detail below by way of example. Show it:

Fig. 1 :

a ventilation situation,

2 a, b:

the dew point as a function of the water vapor partial pressure and the air temperature,

3 :

the dew point temperature as a function of the air temperature and the relative humidity

FIG. 1 shows the typical application in which the ventilation system is installed in a room 50 whose internal air 52 is too humid, for example in a garage or a basement room:
At points as far apart as possible, the air inlet point - in this case, the left air inlet opening 9 - and the air outlet point - in this case the right air outlet opening 11 - is each a motor-driven Fan 1 mounted. The fan 1 on the left side in the air inlet opening 9 has such a direction of rotation that it transports outside air 51 into the space 50 .

The fan 1 shown in the right-hand edge of the image in the air outlet opening 11 in the activated state has such a direction of rotation that it carries away interior air 52 outside the space 50 .

In the deactivated state, the fans 1 or in particular closure flaps 12 fastened to them close the respective openings 9 , 11 as tightly as possible. If only one of the openings 9 , 11 has a fan 1 , then the other opening must have at least such closing flaps 12 which, when the fan 1 is inactive, close the corresponding opening as tightly as possible.

Outside of the space 50 , as close as possible to the air inlet opening 9 , an outdoor sensor 4 is arranged, and within the space 50, an indoor sensor 3, both of which respectively measure in position the prevailing temperature of the air and the relative humidity.

They pass on their measured values to a controller 2 , which is preferably weather-protected, for example, in the interior of the room 50 , and the signal also with the two fans 1 and / or the shutter 12 of the openings 9 , 11 is in communication and these controls , So the fan 1 on or off and possibly regulated in its speed and the shutter 12 opens or closes.

Aeration is only carried out and the at least one corresponding fan 1 is rotated, if the conditions described above are present.

FIG. 2a shows the relationship between the air temperature, the water vapor partial pressure, the relative humidity LF _rel. and the dew point temperature T _T in the form of the so-called dew point curve.

It can be seen that the dew point, ie 100 % relative humidity, plotted against the air temperature, forms an exponentially rising curve and the dew point is present at a different water vapor partial pressure at each temperature.

The air pressure is composed of the partial pressures of the constituents contained in the air, in the case of air laden with water vapor thus the partial pressure of the water vapor, the partial pressure of the oxygen, the partial pressure of the nitrogen and the partial pressure of the other components contained in the air.

If, in a current situation, for example in the form of moist air, their temperature T _L and their relative humidity LF _rel. You can enter this current situation in this diagram in the form of a vertical line at the present temperature:
Their length from the horizontal abscissa to the dew point curve means 100 % rel. Humidity and on this route can from below the current situation x corresponding to the percentage of relative humidity LF _rel. be plotted in the form of this percentage on the mentioned distance from below, eg 42 %.

On the horizontal one can read from this current situation x that the actual water vapor partial pressure is 20 kPa. Where this horizontal intersects the dew point curve, exactly below can be read the dew point temperature T _T for the current situation x.

If, in the current situation, one were to lower the air temperature to the dew-point temperature T _T , the moisture contained in the air would condense as of this temperature and precipitate out as water.

This graph also shows that when the temperature changes, but the amount of dissolved water per unit volume of air remains constant, the relative humidity LF _rel. changes, and thus from this graph, the relationship between absolute and relative humidity can not be determined.

In FIG. 3 on the other hand, the dew point temperature T _{T is} plotted and read in a simple form above the air temperature T _L , specifically for different relative air humidities LF _rel .

For the state inside (I) of a room, the temperature inside as well as the dew point temperature inside T _{Ti is} directly readable.

The situation A 1.1 is recorded as a typical outdoor summer situation, with a temperature significantly higher than that of the interior and a lower relative humidity.

Immediately readable here is that then the dew-point temperature outside T _{TA is} lower than the dew-point temperature inside T _TI , and can be ventilated.

The same applies to the illustrated typical winter situation with A 1.3 , where the outside temperature is significantly lower than the temperature in the interior, but also at a lower relative humidity than in the interior. Again, the conditions for ventilation are given.

At the same time, an exceptional situation in the form of the summer situation is represented as A 1.2 , namely humid, damp summer air, ie at the same high temperature as in A 1.1 , but with significantly higher relative humidity. It is immediately apparent that then the dew-point temperature T _TA outside is higher than the dew-point temperature T _TI inside and should not be aired.

FIG. 2b now shows in a detail situation FIG. 2 a for the relevant temperature range also the situation in the interior (I) as well as the external situation in two typical summer situations A 1.1 and A 1.2 and a typical winter situation A 1.3 .

Since the water vapor partial pressure correlates strongly with the absolute humidity (mass of water per unit volume of air), the vertical coordinate is also to be regarded as absolute humidity.

This also shows immediately that there may be situations like A 1.2 where the dew point temperature T _{TA1.2 is} higher outside than the dew point temperature inside T _Ti , and yet the absolute humidity outside may be higher than inside and thus one Ventilation of the room would be counterproductive.

For absolutely safe ventilation, therefore, the absolute humidities inside and outside would have to be compared with each other, but a much higher evaluation and conversion effort is required in the evaluation of the sensor measured values.

As the situations of A 1.1 and A 1.3 show in comparison to I, however, in most cases a comparison of the dew point temperatures (eg T _Ta1.1 <T _Ti ) is sufficient as the basis for the decision for the ventilation.

LIST OF REFERENCE NUMBERS

1

Fan

2

control

3

internal sensor

4

outdoor sensor

5

temperature difference

7

minimum temperature

8th

display

9

Air inlet opening

10

flow direction

11

Air outlet opening

12

flap

50

room

51

outside air

52

indoor air

LF _rel.

relative humidity

LF _abs.

absolute humidity

p

air pressure

_Ti

Dew point temperature inside

T _Ta

Dew point temperature outside

T _Li

Air temperature inside

T _La

Air temperature outside

X

current situation

Claims (17)

1. A method for ventilating a room (50) by controlled feeding of external air (51) at a feed location of the room (50) and exhausting internal air (52) at an exhaust location remote from the feed location,
   wherein a dew point temperature (T_Ta) of the external air (51) and a dew point temperature (T_Ti) of the internal air (52) are determined from an internal relative humidity and from an internal air temperature measured by an internal sensor (3) and from an external relative humidity and an external air temperature measured by an external sensor (4) by the sensors or by a control,
   characterized in that
   the feeding and exhausting is only performed when the dew point temperature (T_Ta) of the external air (51) is lower by a random selectable and adjustable minimum temperature difference (5) than the dew point temperature (T_Ti) of the internal air (52).
2. The method for cross ventilating the room (50) by controlled feeding of external air (51) at a feed location of the room (50) and exhausting internal air at an exhaust location remote from the feed location, in particular according to claim 1,
   characterized in that
   an absolute air humidity (LF_abs) of the external air (51) and an absolute air humidity (LF_abs) of the internal air (52) is determined from an internal air temperature measured by an internal sensor (3) and an inner relative humidity and an external air temperature measured by an external sensor (4) and an external relative humidity by sensors or by a control, and the feeding and exhausting is only performed when the absolute air humidity (LF_abs) of the external air (51) is lower by an absolute humidity difference which is freely selectable and adjustable, than the absolute air humidity (LF_abs) of the internal air (52).
3. The method according to one of the preceding claims,
   characterized in that
   feeding and exhausting is only performed when the air temperature (T_Ti) in the interior of the room (50) is above a predetermined minimum temperature (7) and/or the feeding an exhausting is terminated when the temperature difference (5) and/or the absolute humidity difference undercuts a predetermined respective minimum difference.
4. The method according to claim 3,
   characterized in that
   feeding and exhausting is performed in intervals when the minimum temperature (7) is detected and the ventilation intervals are not longer than the break intervals, advantageously the ventilation intervals only 1/5, better 1/10, better 1/20^th of a length of the break intervals and/or air pressures for determining absolute humidities are measured by the internal sensor (3) and the external sensor (4).
5. The method according to one of the claims 2 through 4,
   characterized in that
   an average air pressure is presumed for the absolute air humidity (LF_abs) of the internal air (52) or the actually measured air pressure is used in case of an existing air pressure measurement.
6. The method according to one of the preceding claims,
   characterized in that
   a temperature sensor and a humidity sensor of the external sensor (4) and/or of the internal sensor (3) is activated at the most every 1000 ms, wherein a ratio of durations of non-activity to activity of the sensors (3, 4) is increased as a function of the last measured temperature when the temperature has dropped.
7. The method according to one of the preceding claims, characterized in that the absolute air humidity (LF_abs) is determined from the relative air humidity (LF_rel.) and an air temperature (T_L) measured by a sensor (3, 4), in particular based on an average air pressure (p) $$L{F}_{\mathit{abs}.}=\mathrm{216}.7\times \frac{\frac{L{F}_{\mathit{rel}}}{\mathrm{100}\%}\times \alpha \times \exp \left(\frac{\beta \times t\left(°C\right)}{\lambda +t\left(°C\right)}\right)}{\left(\mathrm{273}.\mathrm{15}°C+t\left(°C\right)\right)},$$

   

   wherein Condition t _Range(°C) α (hPa) β λ (°C) Over Water -45-60 6.112 17.62 243.12 Over Ice -80 - 0.01 6.112 22.46 272.62 and/or the dew point temperature is determined from $$T_T\left(L{F}_{\mathit{rel}.},T\left(°K\right)\right)=T_n\times \frac{\mathit{In}\left(\frac{L{F}_{\mathit{rel}.}}{\mathrm{100}\%}\right)+\frac{m\times T\left(°K\right)}{T_n+T\left(°K\right)}}{m-\mathit{In}\left(\frac{L{F}_{\mathit{rel}.}}{\mathrm{100}\%}\right)-\frac{m\times T\left(°K\right)}{T_n+T\left(°K\right)}}$$

   

   wherein T-range T_n (°C) m Over Water 0-50°C 243,12 17,62 Over Ice, -40-0°C 274,62 22,46
8. A ventilation arrangement for ventilating a room (50) by a controlled feeding of external air (51) and exhausting internal air (52), the ventilation comprising:

   - at least one fan (1),

   - an internal sensor (3)

   - an external sensor (4)

   - a control (2) that controls the at least one fan (1) and receives the measuring values of the sensors (3, 4),

   characterized in that

   - the internal sensor (3) and the external sensor (4) are configured to

   - measure the absolute air humidity, or

   - measure the relative air humidity (LF_rel.) and the temperature (T_L.) of the air,

   - the control (2) is configured when measuring the relative air humidity (LF_rel.) and the temperature (T_L.) of the air by the sensors (3, 4) to determine the absolute air humidity (LF_abs) at the internal sensor (3) and at the external sensor (4) therefrom, and

   - the control (2) receives the measurement valves of the sensors (3, 4) and controls at least one fan to feed and exhaust air when the absolute air humidity (LF_abs) of the external air (51) is less than the absolute air humidity (LF_abs) of the internal air (52) by an absolute humidity difference which is freely selectable and adjustable.
9. The ventilation arrangement according to claim 8,
   characterized in that the internal sensor (3) and the external sensor (4) are configured to measure the air pressure (p), and/or
   when the feeding and exhausting is only performed when the absolute air humidity (LF_abs) of the external air is less than the absolute air humidity (LF_abs) of the internal air (52) or the absolute air humidity (LF_abs) of the external air (51) is less by an absolute humidity difference than the absolute air humidity (LF_abs) of the inner air (52) the air pressure (p) is presumed to be an average air pressure or in case of an existing pressure measurement the actually measured air pressure is used.
10. The ventilation arrangement according to one of the preceding device claims,
    characterized in that
    the control (2) is configured to determine the absolute air humidity from the relative air humidity (LF_rel.) and from an air temperature (T_L.) measured by a sensor (3, 4), in particular based on an average air pressure according to the formula: $$L{F}_{\mathit{abs}.}=\mathrm{216}.7\times \frac{\frac{L{F}_{\mathit{rel}}}{\mathrm{100}\%}\times \alpha \times \exp \left(\frac{\beta \times t\left(°C\right)}{\lambda +t\left(°C\right)}\right)}{\left(\mathrm{273}.\mathrm{15}°C+t\left(°C\right)\right)},$$

    

    wherein Condition ^t Range^(°C) α (hPa) β λ (°C) Over Water - 45-60 6.112 17.62 243.12 Over Ice -80 - 0.01 6.112 22.46 272.62
11. The ventilation arrangement according to one of the preceding device claims, characterized in that the control (2) is configured to determine the dew point temperature from $$T_T\left(L{F}_{\mathit{rel}.},T\left(°K\right)\right)=T_n\times \frac{\mathit{In}\left(\frac{L{F}_{\mathit{rel}.}}{\mathrm{100}\%}\right)+\frac{m\times T\left(°K\right)}{T_n+T\left(°K\right)}}{m-\mathit{In}\left(\frac{L{F}_{\mathit{rel}.}}{\mathrm{100}\%}\right)-\frac{m\times T\left(°K\right)}{T_n+T\left(°K\right)}}$$

    

    wherein T-Range T_n (°C) m Over Water , 0-50°C 243-12 17,62 Over Ice , -40-0°C 274,62 22,46
12. The ventilation arrangement according to one of the preceding device claims, characterized in that the control (2) includes a display (8) which displays a dew point temperature (T_T) and/or the absolute air humidity (LF_abs) separately for the external sensor and the internal sensor (4, 3), and/or the control (2) includes a display (8) which displays an actual air temperature (T_L) separately for the external sensor and the internal sensor (4, 3).
13. The ventilation arrangement according to one of the preceding device claims, characterized in that

    - the two sensors (3, 4) and the at least one fan (1) are signal connected with the control (2) wirelessly, in particular by radio, and/or the ventilation arrangement includes two fans (1) at points of the room (50) that are remote from each other, in particular at points of the room (50) that are arranged opposite to each other at a maximum distance.
14. The ventilation arrangement according to one of the preceding device claims,
    characterized in that
    the external sensor or the internal sensor (4, 3) has a processor for determining the dew point temperature and/or absolute air humidity, in particular a chip, in particular a CMOS chip and/or
    the control (2) has a test function for the included relay.
15. The ventilation arrangement according to one of the preceding device claims,
    characterized in that
    the control (2) includes a program for permanent ventilation where ventilation is continuously performed as long as the prerequisite (dew point temperature external (T_Ta) < dew point temperature internal (T_Ti) and optionally additionally absolute air humidity external < air humidity internal) and/or
    the control (2) includes a cooling program where the temperature in the room (50) can be reduced by introducing colder external air as long as a relative and/or absolute air humidity in the room does not exceed a predetermined maximum relative and/or absolute room air humidity.
16. The ventilation arrangement according to one of the preceding device claims,
    characterized in that
    the control (2) includes a heating program according to which the temperature in the room (50) can be increased by feeding warmer external air as long as a relative and/or absolute air humidity in the room does not exceed a predetermined maximum relative and/or absolute air humidity in the room (50), and/or
    the humidity sensor is a capacitive sensor.
17. The ventilation arrangement according to one of the preceding device claims,
    characterized in that
    the temperature sensor is a bend gap sensor, and/or
    the ventilation arrangement is configured so that no significant temperature conduction is performed from the control (2) in particular its processor to the humidity sensor.

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