The invention relates to a device for preventing water vapor condensation on the indoor surface of composite roof windows. The purpose of the device according to the invention is to prevent the formation and accumulation of condensation on roof windows, particularly on the surface of window panes or window frame, and in particular in the lower part thereof.

Surface condensation of water vapor is a phenomenon involving condensation of vapor on the surface of a barrier, and in a particular case - window surface from the warmer side.

Water vapor condensation on the indoor surface of a window may form if the temperature of window surface is lower than the dew point temperature of air close to the window. The formation of surface condensation depends mainly on indoor conditions such as temperature inside a room, air humidity i.e. partial pressure vapor, and air movement in a room, as well as the window structure, its insulation properties and the way it is built in, and also on outdoor conditions such as outdoor temperature and air movement outdoors (wind).

Water vapor condensation on indoor surfaces of roof windows mounted in a sloping roof results in the dripping of condensate down the walls of the room under the window. This makes the window or its elements moist, rooms may get flooded and in consequence floor in the window area and the furnishings placed thereon may get damaged. This phenomenon conduces the formation of mould, loss of wall thermal insulation properties and in consequence intensifies the phenomenon of moistness, and in winter leads to wall frost penetration and damage, and in particular the surface thereof.

This phenomenon makes it impossible to put furniture directly under a window to benefit from sunlight or to observe the night sky.

The possibility of the formation of condensation on the indoor surface of roof windows is checked by comparing the dew point temperature which depends on water vapor amount in the air of the room with temperature of window surface from the indoor side. Dew point temperature may be calculated based on a commonly known approximate formula: 112

where:

t _d - dew point temperature [°C]

t - indoor temperature [°C]

H - relative air humidity inside a room, [ %].

Conditions of water vapor condensation are checked by comparing the dew point temperature which depends on water vapor content in the air of the room with the temperature of indoor window surface. The possibility of the formation of condensation may be calculated based on a known formula: where: vi- temperature of window indoor surface

t - temperature of air inside a room t

* outdoor temperature heat penetration coefficient

(the reverse of heat transfer resistance) k—

window heat transfer coefficient.

If the temperature of a window indoor surface ,· is lower than the dew point temperature, condensation will occur. Thus it is necessary to select or replace a window or equip it with additional accessories which will lower the heat transfer coefficient will thus increase the thermal insulation through adequate additional insulation of the barrier. It is also possible to change humidity conditions in the room e.g. ventilation improvement. Condensation may occur in some parts of a room if they are in a specific place. It usually happens in the bottom part of a window recess where the temperature is lower as a result of air being cooled through the window surface.

In the case of water vapor in the air, the dew point temperature is the temperature in which water vapor in the air reaches the state of saturation due to cooling (with the existing air composition and pressure), and below that temperature it becomes oversaturated and condenses or resublimes. When the saturation state is reached, mist, clouds or precipitation forms in the air, and in closed rooms condensation occurs and water condenses on surfaces.

Apart from the inconvenient wetting of window areas close to roof windows, with water condensing on the indoor surface thereof, there forms a layer of cool air which has been cooled as a result of a contact with frame and glass pane of a roof window mounted on a sloping roof. The layer of forming cool air causes physical discomfort to individuals being in the window zone of the room.

There are various ways to prevent or reduce condensation on the indoor surface of roof windows.

The easiest known way to prevent condensation on the indoor window surface is to increase the dew point temperature and adjust temperature inside the room and humidity of air in the room which contains water vapor by using all kinds of different radiators, often equipped with a fan, most often controlled by means of simple temperature regulators placed directly under a window, most often close to the floor in the case of roof windows. Heaters used were intended mainly for heating the inside of the entire room and were not adjusted to heating windows.

American patent application US5899078 A disclosed a system for reducing power consumption of door and frame heaters of refrigerating devices while maintaining protection against condensation. The system includes one or more condensation sensors attached to the door which are monitored by control circuitry which controls power applied to the door or frame heater. Condensation on the sensor will increase the conductivity of the sensor, which is detected by the control circuitry. When condensation occurs, power is applied to the heater until the condensation is eliminated. The invention includes two different condensation sensor configurations.

International patent application W02005030013 (Al) discloses a system in connection with a cold-storage/freezer space, said cold-storage freezer space comprising at least one door with at least two transparent sheets, a conductive layer being placed on the sheets to function as a heating element to keep said sheets free of condensation, comprises a moisture sensor and a temperature sensor on the side which is warm when using the cold-storage/freezer space. Said sensors are connected to a control unit, said control unit regulating the supply of power to said conductive layer. The system also comprises a second temperature sensor in said cold-storage/freezer space, i.e. on the side which is cold when using the cold-storage/freezer space, said second temperature sensor being connected to said control unit. Canadian patent application CA2942907 (Al) discloses condensation mitigation devices and condensation prediction/detection techniques configured to prevent window condensation with reduced power consumption. A condensation mitigation device is configured to predict and/or detect a window condensation event. The condensation mitigation device is powered on only during such an event, and the condensation mitigation device is powered off afterwards to conserve power.

Also international patent application WO2017162917 (Al) discloses a measurement and control method by means of which condensation generating on a surface is prevented by controlling the heating of the surface by means of control devices, the prevailing dew point temperature is calculated by measuring air humidity and temperature. Temperature of the condensing surface is measured and controlled so that the calculated dew point temperature is used as the set value of the surface temperature. To prevent condensation, safety temperature difference is added to dew point temperature difference and their sum is used as the set value for controlling the temperature of the condensing surface.

Below are definitions of terms used in the description of the device according to the invention:

controller - electronic control system built-in the device and including all set values, data, variables entered in the memory of the device's controller; regulator - a program function operating as a regulator implemented in the controller; outdoor temperature sensor - a sensor for measuring air temperature outside a building; indoor temperature sensor - a sensor for measuring air temperature inside a room with roof windows; humidity sensor - a sensor for measuring relative air humidity inside a room with roof windows; frame temperature sensor - a sensor for measuring temperature of the surface of the window frame of a roof window, mounted in its bottom part in the right or the left corner; dew point module - part of the control logic which keeps the temperature of the surface above the dew point;

convection module - part of the control logic which maintains upward air convection with electricity consumption at the lowest possible level .

The essence of the design of the device according to the invention for the prevention of the condensation of water vapor in rooms on the indoor surface of composite roof windows consists in that the device includes a controller, indoor temperature sensor and optionally a frame temperature sensor and/or outdoor temperature sensor and/or heater temperature sensor, and a heater and possibly a fan and/or a radiator and/or an insulation plate, and has a housing whose size is adjusted to the width of a roof window and can be mounted to a wall of the room or roof window frame, preferably at a distance, and a humidity sensor and/or convection module.

The device has a heater with one-sided thermal insulation from the side of the room, preferably in form of a resistance wire wound on a carrying element.

In a preferred embodiment, the device according to the invention has a heater divided into sections varying in heating power, with extreme sections having power higher than the middle section. The heater of the device may be a plate heater whose structure is sectional and consists of separate heating sections of various heating power whose sides are connected to each other.

In another preferred embodiment, the device may be equipped with a plate heater which has a sectional structure and consists of separate heating sections of equal heating power, whose sides are connected to each other, controlled independently to obtain different heating power.

To improve heat transfer efficiency, the device may be preferably equipped with a radiator with ribs in form of vertical flat continuous or dotted fins. In another preferred case, ribs of both extreme sets of parallel radiator ribs are inclined outwards in opposite directions and are at an angle a falling within the range of 5- 85° off the vertical.

To facilitate air flow, the plate heater, insulation plate and the radiator are at a slight distance from at least one wall of the housing.

Furthermore, to improve the heat transfer efficiency, the device according to the invention is equipped with at least one fan directing a stream of heated air at the window frame. The device may be preferably equipped with two ventilation units, each having at least one fan; built in symmetrically on both sides of the device, on the internal surface of the insulation plate.

To enhance the convection effect, the ventilation unit is preferably equipped with external deflectors placed over suction holes installed on the external surface of the housing. For technological and economic reasons, the external deflectors and the housing are made of one piece of material.

Preferably the housing has holes or catches to mount it to a wall or window frame.

To obtain high efficiency and flexibility of the device's service, the housing has at least one gap along its length from the top; equipped with a fixed or adjustable shutter. The shutter is adjusted manually or mechanically by way of a remote controlled electrical motor.

The device according to the invention has a control system comprising a dew point module and a convection module. Indoor air temperature sensor, window frame temperature sensor, outdoor temperature sensor and a humidity sensor in the control system are connected to the controller by wire or wirelessly.

The device is equipped with a control panel on the housing and may be equipped with a receiver of remote signals introducing settings that are sent from a remote control or an electronic telecommunication device. The length of the device according to the invention is adjusted to the width of a roof window. In a preferred embodiment, the device according to the invention has a modular structure with the central module being the controller unit in a separate housing, and side modules being heating modules connected thereto, with the same or different service parameters and/or dimensions, making it possible to adjust power and length of the entire device to the width of a roof window.

Preferably the window frame temperature sensor is integrated in one housing with the humidity sensor.

In a particularly preferred embodiment, the device according to the invention has an control system additionally equipped with an outdoor temperature sensor.

To obtain additional effect and to combine several functions, the device may be integrated with light e.g. with LED light. The device may also have additional equipment comprising a weather station and/or a radio set.

The control system of the device according to the invention comprises as a standard a controller equipped with a sensor for measuring indoor humidity and an indoor temperature sensor, dew point temperature module using a known approximate formula for calculating the dew point t _d , being a part of the logic intended to keep the surface of a roof window frame at a temperature above the dew point temperature, and a turned on convection module being a part of the control logic intended to keep convection of indoor air at a pre-set level, as well as a regulator that may have a standard on-off characteristics (bistable) or proportional P or proportional - Integral PI or Proportional - Integral - Derivative PID. Parameters including the value of the window heat transfer co-efficient (given by window manufacturer), window surface value, window height, fan activation and a table with fan revolution values against the power value to be emitted by the heater, are entered into the memory of the control system of the device according to the invention, and optionally a co-efficient of the heater temperature to window frame temperature; parameters entered into the memory are used for setting the regulator's parameters.

Optionally, the control system may be equipped with an outdoor temperature sensor and a window frame temperature sensor.

The control system maintains the demanded temperature t _mjn = t _d + DT in the roof window area, where DT is a temperature value reserve - safe added value (offset), preventing condensation, higher by DT > 1 °C from the dew point temperature t thanks to the regulator, it can also ensure constant upward convection of air in the roof window area. The purpose of ensuring upward air convection is to obtain comfortable conditions in the zone under a roof window and prevent the flow of cold air on items placed under a roof window e.g. a bed or an armchair.

In its basic version the device according to the invention may be equipped with a control system comprising a sensor for measuring humidity inside the room and an indoor air temperature sensor; dew point module and turned on convention module.

Dew point module in this system operates as a standard closed-loop control system with feedback.

The pre-set value in this system in the dew point temperature module is temperature t _min , being a total of the dew point temperature t and the reserve value At.

The feedback value is the window frame temperature from the window frame temperature sensor.

Parameters entered into the memory of the device and comprising the value of the window heat transfer co-efficient (given by window manufacturer), window surface value and window height are used for defining PID parameters of the regulator, whereas data comprising fan activation and the table with fan revolution values against the value of power to be emitted by the heater are used for controlling the fan.

In the convection module of this control system the function for calculating convection based on the use of indoor air temperature, frame temperature and parameters comprising the value of window heat transfer co-efficient (given by window manufacturer), window surface value and window height controls the heater so as to keep constant upward air convection with the lowest possible consumption of electric energy.

The control system has a function comparing the power value from the dew point module with the value of power from the convection module and sends to the heater the value of power that is the higher of the two and which should be emitted by the heater.

This value is sent by means of PWM signal or an analog or a digital signal to at least one electric heater equipped with at least one fan controlled by a fan control function based on the value of power to be emitted by the heater, and parameters comprising fan activation and a table with fan revolution values against the power value to be emitted by the heater, entered into the memory of the device.

The device according to the invention may be optionally equipped with a control system comprising a sensor for measuring humidity inside the room and an indoor air temperature sensor; outdoor temperature sensor and a dew point module and a turned on convection module. The dew point module of this system works as an open-loop control system without feedback and based on a pre-set value of t min, outdoor temperature value and parameters comprising value of window heat transfer co-efficient (given by window manufacturer), window surface value and window height. The pre-set value in this system is the demanded temperature t _mjn , being a total of the dew point temperature t _d and the reserve value At.

The dew point module has a function for calculating the power of the heater necessary to keep the temperature of the window frame above the dew point based on the outdoor temperature value and parameters entered into the memory and comprising window heat transfer co-efficient, window surface value and window height.

In the convection module of this control system, the function for calculating convection based on indoor air temperature, outdoor air temperature and parameters entered into the memory of the device and comprising the value of window heat transfer co-efficient (given by window manufacturer), window surface value and window height controls the heater so as to maintain constant upward air convection with the lowest possible consumption of electric energy.

The control system has a function for comparing the value of power from the dew point module with the value of power from the convection module and sends to the heater the value of power that is the higher of the two and should be emitted by the heater.

This value is sent by means of PWM signal or an analog or a digital signal to at least one electric heater equipped with at least one fan controlled by the fan control function based on value of power to be emitted by the heater, and parameters comprising fan activation and a table with fan revolution values against the value of power to be emitted by the heater, entered into the memory of the device.

The device according to the invention may be optionally equipped with a control system comprising a sensor for measuring humidity inside a room, an indoor air temperature sensor; outdoor temperature sensor and a roof window frame temperature sensor and a dew point module and a turned on convection module.

The dew point module in this system operates as a standard closed-loop control system with feedback. The pre-set value in this system is the demanded temperature t _min , being a total of the dew point temperature t _d and the reserve value At. The feedback value is the window frame temperature from the frame temperature sensor.

Outdoor air temperature and parameters comprising the value of the window heat transfer co-efficient (given by window manufacturer), window surface value and window height are used for setting PID parameters of the regulator, whereas data comprising fan activation and the table with fan revolution values in against the value of power to be emitted by the heater are used for controlling the fan.

In this system the function for calculating convection based on indoor air temperature, frame surface temperature, outdoor air temperature and parameters entered into the memory of the device and comprising the value of window heat transfer co-efficient (given by window manufacturer), window surface value and window height controls the heater so as to keep constant upward air convection with the lowest possible consumption of electric energy.

The control system has a function for comparing the value of power from the dew point module with the value of power from the convection module and sends to the heater the value of power that is the higher of the two and should be emitted by the heater.

This value is sent by means of PWM signal or an analog or a digital signal to at least one electric heater equipped with at least one fan controlled by a fan control function based on the value of power to be emitted by the heater, and parameters comprising fan activation and a table with fan revolution values against the value of power to be emitted by the heater, entered into the memory of the device.

The device according to the invention may be optionally equipped with a control system provided with a sensor for measuring humidity inside the room, an indoor air temperature sensor, heater temperature sensor and a dew point module and a turned on convection module.

Dew point module in this system operates as a standard closed-loop control system with feedback.

The pre-set value in this system is the demanded temperature t _min , being a total of the dew point temperature t _d and the reserve value At. The feedback value is the frame temperature calculated by the function based on total power supplied to the heater and heater temperature and parameters entered into the memory and comprising the value of the window heat transfer co-efficient (given by manufacturer); window surface value and window height.

Co-efficient of the ratio of heater temperature to the frame temperature is established empirically and provided to the frame temperature calculation function in parameters entered into the memory and additionally comprising the value of the window heat transfer co-efficient (given by manufacturer), window surface value and window height and the co-efficient of the ratio of heater temperature to roof window frame temperature. Parameters entered into the memory of the control system are also used for defining PID parameters of the regulator.

The system works based on the principle that the lower the window frame temperature before the heater in a spot where the heater sensor is located, the lower the heater temperature with the same power supplied to the heater.

In the convection module of this system the convection calculation function uses the calculated value of the temperature of roof window frame surface, indoor temperature value and parameters entered into the memory and comprising the value of window heat transfer co-efficient (given by window manufacturer), window surface value and window height, and controls the heater in such a way as to maintain constant upward air convection with the lowest possible consumption of electric energy. The control system has a function comparing the value of power from the dew point module with the value of power from the convection module and sends to the heater the value of power which is the higher of the two and should be emitted by the heater.

The value is sent by means of PWM signal or an analog signal or a digital signal to at least one electric heater connected to at least one fan controlled by a fan control function based on the value of power to be emitted by the heater, and parameters comprising fan activation and a table with fan revolution values against the value of power to be emitted by the heater, entered into the memory of the device.

The device according to the invention was presented in exemplary embodiments thereof on attached drawings where:

Fig. 1 shows the device from the side of the room wall in an exploded perspective view;

Fig. 2 shows the perspective view of a two-fan unit;

Fig. 3 shows a part of the device according to the invention in a perspective view, with exposed cross-section (vertical),

Fig. 4. shows a radiator with the heater connected thereto in a perspective view from the side of the heater;

Fig. 5 shows a) table with example distribution of power along the length of the heater, b) a front view of one-piece heater with visible zones varying in power, c) front view of a multi-part heater made of plate heating sections of equal power connected separably to one another; Fig. 6 shows a) radiator with ribs in form of continuous fins from the front view, b) radiator with ribs in form of dotted fins from the front view, c) radiator with a central set of vertical ribs and extreme sets or ribs inclined by the angle a from the front view, d) radiator from the side view, e) radiator from the top view and f) radiator from the perspective view, from the front, from the wall side,

Fig. 7 shows the device according to the invention in a) top view, b) side view, c) schematic view of the device with directions of air stream flows indicated,

Fig. 8 shows schematically an exemplary location of the device under a roof window with air flow indicated,

Fig. 9 shows schematically an exemplary location of the device with a roof window and highlighted mounting point of the window frame temperature sensor,

Fig. 10 shows a schematic diagram of an embodiment of the control system,

Fig. 11 shows a schematic diagram of another embodiment of the control system Fig. 12 shows a schematic diagram of another embodiment of the control system,

Fig. 13 shows a schematic diagram of another embodiment of the control system.

Below is the explanation of numbers on schematic diagrams of the control system in embodiments of the device according to the invention shown on Fig. 10, Fig. 11 , Fig. 12 and Fig. 13 :

101. Sensor for measuring humidity of air inside the room . Air humidity level inside the room

. Sensor for measuring temperature of air inside the room

. Value of air temperature inside the room

. Function for calculating approximate dew point temperature according to the formula:

where:

t _d - dew point temperature 6 [°C]

t - temperature of air inside the room 4 [°C]

H - relative humidity of air inside a room 2 [ %] . . Dew point temperature

. Value of temperature reserve At ( > 1 °C )

. The function of arithmetic addition of the dew point temperature t to reserve temperature At .

. The value of demanded temperature t _mjn ; being a result of the addition of the value of dew point temperature t and the value of temperature reserve

At.

. The function of arithmetic subtraction; calculation of the difference between the value of demanded temperature t _mjn and the value of frame temperature

[measured (111) or calculated (121)], . Value of the window frame temperature (111) measured in its bottom part on the left or the right side,

. Error value as the input value for the regulator;

. regulator - a regulator function of the following standard characteristics: bistable or Proportional P or Proportional - Integral PI or Proportional - Integral - Derivative PID.

. Value of power to be emitted by the heater [from the dew point module (128)]; sent by means of PWM signal or an analog signal or a digital signal.

. At least one electrical heater;

. Roof window frame surface temperature sensor installed close to the right bottom or left bottom corner of the window

. Function for calculating power to be emitted on the heater based on the demanded temperature t _min (109), outdoor air temperature (120) and the coefficient and parameters (118);

. Parameters entered into the memory of the device:

- window heat transfer co-efficient given by window manufacturer

- window surface

- window height

- co-efficient of the ratio of heater temperature value to frame temperature;

- fan activation and

table with fan revolution values against the value of power to be emitted by the heater; . Outdoor air temperature sensor

. Outdoor air temperature

. Calculated temperature of the window frame surface in the vicinity of the right bottom or left bottom corner of the window

. Function calculating window frame temperature based on the measured temperature (123) of the heater (115) and value of power (127) supplied to the heater (115)

. measured temperature of the heater (115)

. Switch or value entered into the memory of the device which activates or deactivates the convection maintenance function.

. Value of power to be emitted by the heater [from the convection module (129)]; sent by means of PWM signal or an analog signal or a digital signal.. Function comparing the value of power (114) from the dew point module (128) with the value of power (125) from the convection module (129) and supplying to the heater (115) the value of power that is higher.

. Value of power to be emitted by the heater (115) sent by means of PWM signal or an analog signal or a digital signal.

. Dew point module - part of the control logic which maintains the temperature of the surface above the dew point.

. Convection module - part of the control logic which maintains upward air convection with electricity consumption at the lowest possible level 130. Temperature sensor of the heater (115); the device according to the invention may be equipped with more than one of those sensors, which makes it possible to measure temperature of various areas of the surface located before the device.

131. At least one fan

132. Value of rotational speed to be reached by the fan (131), sent by means of PWM signal or an analog signal or a digital signal.

133. Function controlling the fan (131) based on the value of power (127) to be emitted by the heater (115) and parameters (118) entered into the device.

134. Function which maintains upward air convection with electricity

consumption at the lowest possible level

The device according to the invention has a box openwork housing 1, equipped with mounting elements in form of lifting slings for mounting directly under the frame 2_of a roof window 3. The housing 1 is equipped with an external control panel 4. Inside the housing 1 there is an insulation plate 5 made of a mat with heat transfer co-efficient of 0,021 W/mK, and plate heater 6 divided into sections varying in temperature, adjacent on one side to the radiator 7. Extreme sections of the plate heater 6 have the working temperature higher than the temperature of the middle section. Plate heater 6 comprises a plate made of electro insulating heat-resistant laminate from glass fiber with resistance wire 8 laminated in and distributed unequally, symmetrically to the center of the heater 6, more dense in the extreme sections of the heater 6. Maximum working temperature on the housing 1 does not exceed 70°C.

On the other side there is a plate heater 6 stuck to the plate radiator 7 whose one side is flat and the other side has ribs and comprises a central set of parallel vertical ribs 9 and two side sets of side ribs parallel to each other 10, inclined upwards outside at an angle of a = 65°off the vertical, which divide the heated air stream and direct part of the stream at the sides of the window 3 to simultaneously eliminate conditions facilitating water vapor condensation and to cause upward air convection in the area adjacent to the window 3.

In another embodiment the ribs 9 of the radiator 7 are vertical flat continuous or dotted fins.

To ensure free flow of air inside the housing 1, the heater 6, insulation plate 5 and the radiator 7 are about 3mm away from the bottom of the housing 1.

The device has two ventilation units mounted on the front of the insulation plate of which each has two fans 11, built-in symmetrically on both sides, on the internal surface of the insulating plate 5. The housing 1 has two pairs of suction holes 12 located symmetrically on the sides of the head wall of the housing and corresponding to the location of the fans 11, shielded with deflectors 13.

The housing 1 has several gaps 14 along its length from the top, equipped with an adjustable shutter 15. The shutter 15 is adjusted by means of a remote controlled electrical engine. In another embodiment the heater 6 has a sectional structure and consists of separate plate heating sections of equal heating power, whose sides are connected to each other, controlled independently to obtain different heating power.

Controller of the device, depending on the embodiment, is equipped with a sensor (101) for measuring air humidity inside the room, sensor (103) for measuring air temperature in the room, and depending on the embodiment, a sensor (116) for measuring temperature of the window frame 2 and a sensor (119) for measuring outdoor temperature (120), it is also equipped, depending on the embodiment and needs, with an on-off regulator (113) or proportional P regulator (113) or proportional - Integral PI regulator PI (113) or Proportional - Integral - Derivative PID regulator (113).

Depending on the embodiment of the device according to the invention, temperature sensors (119), (103) and (116) and the humidity sensor (101) are connected to the controller by wire or wireless connection.

The device according to the invention has in its embodiment a receiver of remote signals introducing settings which are sent from the remote control. In another embodiment the device according to the invention comprises a receiver of an electronic signal of a telecommunication device which may be, depending on the embodiment, a mobile phone signal or a signal of a computer connected to the

Internet network.

To ensure efficient operation of the device according to the invention along the entire width of a roof window 3, the width of the device is adjusted to the width of the window frame 2.

In a specific embodiment, the device according to the invention has a modular structure with the central module being the controller in a separate housing, and side modules being independent heating modules or heating and ventilation modules with different service parameters and/or various dimensions connected thereto, making it possible to adjust the entire device to the width of a roof window 3.

In another embodiment the device has a sensor (116) measuring temperature (111) of frame 2, which is integrated in one housing with the humidity sensor (101).

The device according to the invention is equipped in its basic version with a control system provided with a sensor (101) for measuring humidity inside a room, sensor (103) for measuring temperature (104) of indoor air and sensor (116) for measuring temperature (111) of window 3 frame 2, dew point module (128) and turned on convection module (129). Dew point temperature module (128) in this system operates as a standard closed-loop control system with feedback. The pre set value (109) in this system in the dew point temperature module (128) is the value of the demanded temperature t _mjn , being a total of the dew point temperature t _d (106) calculated by means of a known function (105), plus the added value of the reserve At (107). The feedback value is the temperature (111) of the window frame from the sensor (116) for measuring temperature of the window 3 frame 2. Parameters (118) entered into the memory of the device and comprising the value of the window heat transfer co-efficient (given by window manufacturer), window surface value and window height are used for setting PID parameters of the regulator (113), whereas data comprising fan activation and the table with fan revolution values against the value of power to be emitted by the heater are used for controlling the fan (131).

In the convection module (129) of this control system the function for calculating convection based on the indoor air temperature (104), temperature of the frame (111) and parameters (118) comprising the value of window heat transfer co-efficient (given by window manufacturer), window surface value and window height controls the heater (115) so as to keep constant upward air convection with the lowest possible consumption of electric energy.

The control system performs the function comparing the value of power from the dew point module (128) with the value of power from the convection module (129) and sends to the heater (115) the value of power (114)(125) that is the higher of the two and which should be emitted by the heater (115).

This value is sent by means of PWM signal or an analog or a digital signal to an electric heater (115) equipped with a fan (131) controlled by the fan control function based on the value of power (127) to be emitted by the heater (115) and parameters (118) entered into the memory of the device and comprising fan activation and a table with fan revolution values against the value of power (127) to be emitted by the heater (115).

In another embodiment, the device according to the invention is equipped with a control system provided with a sensor (101) for measuring humidity inside a room, sensor (103) for measuring temperature (104) of indoor air and sensor (119) for measuring outdoor temperature (120) and a dew point module (128) and a turned on convection module (129). Dew point module (128) of this embodiment operates as an open-loop control system without feedback based on the pre-set value, which is the demanded temperature t min (109), being a total of the dew point temperature t d (106) and the value of the reserve At (107), and on the value of outside temperature (120) and parameters (118) entered into the memory of the device and comprising the value of window heat transfer co-efficient

(given by window manufacturer), window surface value and window height.

The dew point module (128) has a function (117) for calculating the power of the heater (115) necessary to keep the temperature of the window frame (2) above the dew point based on the value of outdoor temperature (120) and parameters (118) entered into the memory and comprising the value of window heat transfer co- efficient, window surface value and window height.

In the convection module (129) of this control system, the function for calculating convection based on outdoor air temperature (120), indoor air temperature (104) and parameters (118) entered into the memory and comprising: value of window heat transfer co-efficient (given by window manufacturer), window surface value and window height, controls the heater (115) so as to maintain constant upward air convection with the lowest possible consumption of electric energy.

The control system has a function comparing the value of power (114) from the dew point module (128) with the value of power (125) from the convection module (129) and sends to the heater the value of power (114)(125) that is the higher of the two and which should be emitted by the heater (115). This value is sent by means of PWM signal or an analog or a digital signal to an electric heater (115) equipped with a fan (131) controlled by a fan control function based on the value of power (127) to be emitted by the heater (115) and parameters (118) entered into the memory of the device and comprising fan activation and a table with fan revolution values against the value of power (127) to be emitted by the heater (115).

In another preferred embodiment, the device according to the invention is optionally equipped with a control system provided with a sensor (101) for measuring humidity inside a room, sensor (103) for measuring temperature (104) of indoor air, sensor (119) for measuring outdoor temperature (120) and a sensor (116) for measuring temperature (111) of a roof window 3 frame 2 , and dew point module (128) and turned on convection module (129). Dew point module (128) in this system operates as a standard closed-loop control system with feedback. The pre-set value in this system is the demanded temperature t _mjn (109), being a total of the dew point temperature ta (106) and the pre-set reserve value At (107). The feedback value is the window frame temperature (111) from the frame temperature sensor.(116).

In the convection module (129) of this control system, the function for calculating convection based on the outdoor air temperature (120), indoor air temperature (104), frame temperature (111) and parameters (118) entered into the memory and comprising: value of window heat transfer co-efficient (given by window manufacturer), window surface value and window height, controls the heater (115) so as to maintain constant upward air convection with the lowest possible consumption of electric energy.

The control system has a function comparing the value of power (114) from the dew point module (128) with the value of power (125) from the convection module (129) and sends to the heater (115) the value of power that is the higher of the two (114)(125) and which should be emitted by the heater (115). This value is sent by means of PWM signal or an analog or a digital signal to an electric heater (115) equipped with a fan (131) controlled by a fan control function based on the value of power to be emitted by the heater (115) and parameters entered into the memory of the device and comprising fan activation and a table with fan revolution values against the value of power to be emitted by the heater (115). In another preferred embodiment, the device according to the invention is optionally equipped with a control system provided with a sensor (101) for measuring humidity inside a room, sensor (103) for measuring temperature (104) of indoor air and sensor (130) for measuring temperature (123) of the heater and a dew point module (128) and turned on convection module (129).

The dew point module (128) in this system operates as a standard closed- loop control system with feedback. The pre-set value in this system is the demanded temperature t _mjn (109), which is a total of the dew point temperature t _d (106) and value of the reserve D t (107).

The feedback value is the temperature of the window frame (121) calculated by the function (122) based on total power (127) supplied to the heater (115) and heater temperature and parameters (118) entered into the memory and comprising value of the window heat transfer co-efficient (given by window manufacturer); window surface value and window height. The lower the temperature of the frame surface before the heater (115) at a point where the sensor (130) of the heater (115) is located, the lower the temperature (123) of the heater (115), with the same power (127) supplied to the heater (115). Co-efficient of the ratio of heater temperature to the frame temperature is established empirically and provided to the function (122) for calculating frame temperature in parameters (118) entered into the memory and additionally comprising the value of the window heat transfer co-efficient (given by manufacturer), window surface value and window height and the co-efficient of the ratio of heater temperature to roof window frame temperature. Parameters (118) entered into the memory are also used for establishing PID parameters of the regulator (113).

In the convection module (129) of this system, the function (134) for calculating convection uses the calculated value of temperature (121) of the surface of frame 2 of a roof window 3 value of indoor temperature (104) and parameters (118) entered into the memory and comprising the value of the window heat transfer co-efficient (given by manufacturer) , value of window surface and window height and the co-efficient of the relation of temperature (123) of the heater (115) to the temperature (111) of the frame 2 of a roof window 3, and controls the heater (115) so as to keep constant upward air convection with the lowest possible consumption of electric energy. The control system has a function comparing the value of power (114) from the dew point module (128) with the value of power (125) from the convection module (129) and sends to the heater (115) the value of power that is the higher of the two (114)(125) and should be emitted by the heater (115).

This value is sent by means of PWM signal or an analog or a digital signal to an electric heater (115) equipped with a fan (131) controlled by a fan control function based on the value of power to be emitted by the heater (115) and parameters entered into the memory of the device and comprising fan activation and a table with fan revolution values against the value of power to be emitted by the heater (115).

In all control systems of the embodiments of the device according to the invention, heaters are controlled by means of PWM signal or an analog signal or a digital signal.

The device according to the invention is characterized by stable operation and high efficiency and effectiveness in preventing condensation of water vapor on roof windows 3 in a wide range of temperatures and highly changeable weather conditions. The device according to the invention simultaneously ensures that stable exchange of convection air and convenient temperature are maintained in areas surrounding roof windows 3, facilitating the use of space under roof windows 3. The device may also be used in the case of building facilities with sloping roofs with roof windows 3, as well as big and small oblique glazed surfaces.

List of numbers on Fig. 1 -Fig. 9:

1. Housing

2. Roof window frame

3. roof window

4. Control panel

5. insulation plate

6. Plate heater

7. Radiator

8. resistance wire

9. radiator's vertical ribs

10. radiator's side ribs

11. Fan

12. Suction hole

13. Deflector

14. Top gaps of the housing

15. Top gap shutter

Explanation of numbers on the schematic diagrams of the control system in embodiments of the device according to the invention, presented on Fig. 10 , Fig. 11 , Fig. 12 and Fig. 13 :

101. Sensor measuring humidity of air inside a room

102. Air humidity level inside a room

103. Sensor measuring temperature of air inside a room

104. Value of air temperature inside a room

105. Function for calculating approximate dew point temperature according to the formula:

112 where:

t _d - dew point temperature 6 [°C]

t - temperature of air inside a room 4 [°C]

H - relative humidity of air inside a room 2 [ %].

106. Dew point temperature t

107. Value of temperature reserve At ( > 1 °C )

108. The function of arithmetic addition of dew point temperature t _d to temperature reserve At .

109. The value of demanded temperature being a result of the addition of the value of dew point temperature t _d and the value of temperature reserve At.

110. The function of arithmetic subtraction; calculation of the difference between the value of demanded temperature t _mjn and the value of frame temperature [measured (111) or calculated (121)],

111. Value of the window frame temperature measured in its bottom part on the left or the right side,

112. Error value as the input value for the regulator

113. Regulator - a regulator function of the following standard characteristics: bistable or Proportional P or Proportional - Integral PI or Proportional - Integral - Derivative PID.

114. Value of power to be emitted by the heater [from the dew point module (128)]; sent by means of PWM signal or an analog signal or a digital signal.

115. At least one electrical heater;

116. Roof window frame surface temperature sensor installed in the right bottom or left bottom corner of the window

117. Function for calculating power to be emitted on the heater based on the demanded temperature t _min (109), outdoor air temperature (120) and the co-efficient and parameters (118);

118. Parameters entered into the memory of the device: window heat transfer co-efficient given by window manufacturer

- window surface

- window height

- co-efficient of the ratio of heater temperature value to frame temperature;

- fan activation

- table with fan revolution values against the value of power to be emitted by the heater;

. Outdoor air temperature sensor

. Outdoor air temperature

. Calculated value of temperature of the window frame surface close to the right bottom or left bottom corner of the window. Function calculating window frame temperature based on the measured temperature (123) of the heater (115) and value of power (127) supplied to the heater (115)

. Heater (115) measured temperature,

. Switch or value entered into the memory of the device which activates or deactivates the function of maintaining the convection.. Value of power to be emitted by the heater [from the convection module (129)]; sent by means of PWM signal or an analog signal or a digital signal. . Function comparing the value of power (114) from the dew point module (128) with value of power (125) from the convection module (129) and supplying to the heater (115) the value of power that is the higher of the two.

. Value of power to be emitted by the heater (115); sent by means of PWM signal or an analog signal or a digital signal.

. Dew point module - part of the control logic which maintains the temperature of the surface above the dew point.

. Convection module - part of the control logic which maintains upward air convection with electricity consumption at the lowest possible level

. Heater temperature sensor; device according to the invention may be equipped with more than one of those sensors, which makes it possible to measure temperature of various areas of the surface located before the device.

. At least one fan

. Value of rotational speed to be reached by the fan (131); sent by means of PWM signal or an analog signal or a digital signal.

. Function controlling the fan (131) based on the value of power

(127) to be emitted by the heater (115) and parameters (118) entered into the device. 134. Function responsible for maintaining upward air convection with electricity consumption at the lowest possible level