Windcatchers provide natural office ventilation.

Monodraught Windcatcher systems use established atmospheric principles and the natural effects of the wind to bring fresh air into a building and extract stale warm air, using only natural forces.

When Workspace Group, the leading provider of flexible business space to SMEs in and around London, insisted on natural ventilation for the new third floor offices at its Canterbury Court development, award-winning building services engineers Brian Warwicker Partnership proposed Monodraught Windcatchers, a solution based on sustainability and intelligent design.

Canterbury Court is a 180-year-old building that has, in its distant past, been used as accommodation for horse driven Hackney carriages.

Today, following refurbishment and an extension, this striking modern development located within the Kennington Park Business Centre, offers a combination of warehouse and office space with industrial units located on the lower ground floor and offices above.

A new third floor, added as part of the refurbishment and development project, provides additional office accommodation and features a central atrium and roof garden.

The newly-built third floor was constructed in accordance with Parts L2A and Part F of the Building Regulations and, as Kevin Horsfall of Brian Warwicker Partnership explains, Workspace Group also insisted that the offices had to be naturally ventilated in order to reduce CO emissions.

Commenting on the specification, he says the depth of the office space exceeded the 6.5 metre CIBSE criteria for single-sided, naturally-ventilated accommodation, so a system of roof mounted Monodraught Windcatcher units was proposed to provide crossflow ventilation in each of the office spaces.

Designed to operate with virtually no moving parts, Monodraught Windcatcher systems use established atmospheric principles and the natural effects of the wind to bring fresh air into a building and extract stale warm air, using only natural forces.

Warm air rising to roof level decreases the air pressure within buildings, allowing cooler air to enter the building via the Windcatcher units.

The resultant change in air pressure produces sufficient airflow to make the space comfortably fresh.

Wind blowing onto the windward side of a ventilation stack increases the through-put of air and encourages stale and stagnant air to be extracted through the leeward side of the roof unit.

The fifty-five Windcatcher units installed feature automatic dampers that open and close to maintain comfortable internal temperatures.

The dampers themselves are equipped with individual controls to prevent over-cooling in winter months and provide the occupants of each room with a manual override facility.

The units are designed to accommodate an average heat gain of 35w/m in the offices at a minimum wind speed of 1.5 m/s, but will achieve greater gains with a more normal wind speed of 3 m/s, resulting in a higher internal air change rate.

The cooling effect of the Windcatchers can be further improved in the summer by opening the window lights or external doors in each unit to increase the air change rate.

During winter months the Windcatchers also provide trickle ventilation, supplementing the 5 l/s per person that trickle vents typically offer, to ensure compliance with the new Part F minimum requirement of 10 l/s per person.

Kevin Horsfall says the Windcatcher installation at Canterbury Court not only meets Workspace's brief but also reflects Brian Warwicker Partnership's view that the best of traditional and modern technologies should be used to lower emissions and maximise comfort.

Summing up, he says: "Using natural ventilation with radiator heating for the winter, with a central plant and a limited amount of heat recovery, this 'green' building complies with all current regulations without the need for mechanical cooling".

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