Natural Ventilation Systems August 2009 Part of the VKR Group

The principle of encapsulating any prevailing winds and using this natural resource as a form of ventilation originated some 2,000 years ago in the Middle East, where "wind towers" were often a common sight, but the principle is still used today. The Monodraught Windcatcher is an extension of that principle but is also a development of the highly successful Monodraught Vertical Balanced-Flue System patented in 1965 which has now been utilised by almost all leading companies in the UK to provide optimum ventilation for any boiler house configuration. Clean, fresh air, relatively free from contamination...

Since its inception, Monodraught Ltd has always sought to invent, explore and develop innovative concepts. In 1990 Monodraught launched the Windcatcher Natural Ventilation system, which was based on the original Vertical Balanced-Flue arrangement and combines all the advantages of passive stack and wind driven natural ventilation. Professor Terry Payne, founded the Company in 1974. Since then the company has specialised in the development of natural ventilation and low energy systems and products for the built environment. A significant feature of the Monodraught product range is the high level...

Putting our natural resources to work Why choose natural ventilation ? 4 Monodraught Natural Ventilation Natural ventilation brings in a steady supply of fresh air into the building, topping up the oxygen level, whilst at the same time expelling stale air to atmosphere using the natural buoyancy of thermal forces. Fan Noise often associated with mechanical systems or air conditioning is virtually eliminated to the benefit of the occupants. 2It is healthier Since natural ventilation systems have generally speaking essentially no moving parts, there is nothing to wear out, break down, corrode,...

Why choose ? Monodraught Windcatcher 5 Putting our natural resources to work Early naturally ventilated buildings relied purely on a passive stack approach to act like a ‘chimney stack’. The limitation of such an arrangement is that to work effectively, the temperature in the passive stack has to be some 10°C above the ambient temperature in the room, which in summer months may lead to overheating. Windcatchers overcome this problem by incorporating wind driven air intakes to generate a positive pressure in the room below and combined with temperature differential this assists the passive stack...

Natural ventilation systems 6 Monodraught Windcatcher How does work ? Daytime Operation In the Summer months, perimeter windows can be utilised to aid cross flow ventilation. With fresh air coming in through the windows on the windward side of the building, stale air will be exhausted through the passive stack element of the Windcatcher system. Warm air will naturally rise to ceiling level but at the same time any prevailing wind on the Windcatcher system carries a supply of fresh air down into the room below, thereby slightly pressurising the building and increasing the outward flow of stale...

A fully programmable Automatic Control Panel is provided as standard in the Monodraught package. These panels can be controlled by either temperature or CO2 sensors, depending upon the requirements of each specific application. Rain sensors are included as standard. These panels can serve multiple rooms and are supplied in four standard configurations to meet the project requirements. Temperature One or more temperature sensors are normally positioned in the room to achieve an average reading. This is the simplest method of automatic control and is suitable for most applications. The dampers...

Classrooms and other teaching spaces are one of the main areas where natural ventilation is vital for the wellbeing of the occupants. The Government guidelines on ventilation for educational buildings have changed. The DfEE document, BB87, concentrated on internal temperatures as the overriding factor to determine ventilation levels. However, BB101 concentrates more on air quality than on internal temperature and provides guidelines on acceptable levels of CO2 over the course of the School day. A figure of 1,500 parts per million (ppm) as an average over the day has been adopted in the document,...

Where it is necessary to provide natural ventilation on multifloor installations, Monodraught Windcatcher systems have provided an effective solution. Each room should be served by a separate duct to avoid problems of cross talk and acoustic lining can be provided, where required, to eliminate the ingress of external traffic noise. Motorised dampers and eggcrate ceiling grilles can either be located at ceiling level to each duct or the duct can be turned through 90° at ceiling level. This is now a typical arrangement for schools whereby multiple floors are common place. Rectangular shaped systems...

The demands on Designers for such Projects is considerable. Schools in inner cities suffer from even higher adverse external ambient conditions than the rest of the country but the demand for energy free solutions is even greater. A counter argument put forward against the use of natural ventilation for inner city Schools is the question of air pollution related to air quality. Monodraught’s answer to that is that children still have to travel to School, they often walk to School, and they still probably go out to play between Classes! The alternative cost of filtration and cooling by mechanical...

11 Acoustic issues are increasingly important with the stringent requirements of BB93 and the dilemma faced by many Designers of the need to have openable windows, which themselves are prone to noise ingress. It is considered that by drawing air from above roof level, that in itself avoids the problems of traffic noise as compared to low level windows but the Monodraught design, with the relatively large internal ducts in a cruciform design, lends itself ideally to the application of acoustic material. Acoustics Acoustic matters In January 2005, Monodraught commissioned the Building Research...