The Windcatcher arrangement, pioneered by Monodraught, is now widely recognised as the most reliable and effective means of harnessing the wind’s potential as a renewable energy source.
Wind Driven
Windcatcher technology provides natural ventilation without any moving parts. Using compartmentalised vertical vents, fresh air is brought into the room and stale warm air expelled using the natural effects of the wind.
The system works through normal atmospheric properties where warm air rises and decreases the air pressure within a room so that cooler air falls into the room. This is a subtle change in air pressure and it produces only enough airflow to make the room comfortably fresh.
Stale and stagnant air is extracted by the wind blowing onto the wind-ward side of the windcatcher, with the stuffy air going out through the leeward side of the ventilation stack.
Temperature Driven
Stack effect is achieved as a result of the difference between the air temperature inside and outside of a building – and the subsequent imbalance effect on air density and pressure gradient of the internal and external air masses, results in the warm air rising up through the quadrants.
Fire Dampers
Fire dampers can easily be incorporated into the design of the Monodraught ventilation stacks without in any way having any bearing on the effectiveness of the natural ventilation system. All Monodraught systems are manufactured in glassfibre with Class 1 fire retardant resin.
Security
Clearly it is not possible to break in to or out of a building through the Monodraught Windcatcher system but, nevertheless, stainless steel security grilles can be incorporated into the base of the system.
Multi Floor Operation
The 24 Windcatcher systems installed at St Annes School, Jersey, serve classrooms on both ground floor and first floor, but in addition, the Monodraught systems provide ventilation to the adjoining corridors. Internal dividers and wind turning vanes within the Monodraught Windcatcher system are designed in such a way to ensure that both intake and extract by natural ventilation will take place irrespective of wind direction.
Noise Transmission
The Monodraught Windcatchers were submitted to the BRE Acoustics Centre in January 2002 and 2005 for a series of tests. It was established that in its standard format, the arrangement of the Windcatcher systems has the effect of reducing noise transmission by 26dB as compared to an open window. By incorporating 15mm acoustic lining to the trunk, a minimum of a further 10dB was achieved. Acoustic pods or other forms of attenuation
can also be incorporated.
Windows and Door Openings
In summer months doors and windows are more likely to be opened and this will aid cross flow ventilation, with fresh air coming in through windows on the windward side of the building and be exhausted through the passive stack element of the Monodraught system. Warm air will naturally rise and be exhausted through this passive stack element. In addition natural ventilation will be aided by the external wind movement, creating a negative or suction zone to one side of the Monodraught system as well as the building, which has the effect of slightly pressurizing the building.
The advantage however of the Monodraught system is that it is not dependent on openable windows or vents in the side of the building and in mid season or during daytimes or weekends when perhaps the building is not being used and all the external windows are closed, the Monodraught Windcatcher will still continue to operate, providing all the benefits of this ‘free air conditioning’. The volume control dampers at the base of the Monodraught system at ceiling level will precisely control the amount of airflow through the system.
Night-Time Cooling
Night-time cooling or ‘free cooling’ is considered to be one of the most important aspects of natural ventilation strategies. The volume control dampers can be programmed to open fully at, say, midnight to encapsulate the cool night air. Any prevailing wind carries this air down into the building below.
The ‘cleansing’ effect of the downwash of cold air leaves the building interior feeling fresh and clean for the benefit of the occupants arriving in the morning. The dampers would normally be programmed to close again at, say, 6.00am and a temperature limit can be introduced to ensure that the building is not over-cooled. All this, without compromising the security of the building.
Temperature Control
Monodraught systems are fitted with insulated volume control dampers controlled by temperature and co2 sensors. These dampers control the rate of ventilation dependent on internal temperature.
The systems can be controlled either individually or by a central control panel. The control panel is fitted with a spring/summer/autumn/winter switch, so that the opening of the dampers for night time cooling only occurs during summer months. At other times of the year the dampers can be set to say 3% to 5% to open, this will allow trickle ventilation, whilst avoiding the problems of cold draughts.
Maintenance
A particular feature of Monodraught systems is the emphasis on low maintenance. Manufactured in GRP, all Monodraught systems are covered by a unique 10 year guarantee. Dampers and controls fitted into the systems will be covered by the
normal manufacturer's warranty.
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