Ventilation: Continuous Extract

In our second post of this series on ventilation, we will look at another method that uses trickle vents as the basis for overall building ventilation.

Q: What is continuous extract ventilation?

A: Ventilation is provided via continuous mechanical mechanism either via individual room extracts, a central extract system or a combination of both. Trickle vents or bespoke wall-mounted vents deliver cold, unfiltered make-up air into the dwelling; and warm air will be lost from them. Window openings normally need to be sized accordingly to accommodate them.

Q: Who calculates the required amount of ventilation?

A: The calculation is complex as it includes things like typical wind speeds and should be carried out by a specialist consultant or subcontractor. The rate of extract is set by Building Regulations.

Q: How is moist and stale air extracted from the building?

A: Moist air is typically extracted via a continuous fan from the wet rooms, utility rooms and the kitchen; and will be exhausted via a duct to the outside. Any heat in the air will be lost to the outside. The ducts are typically plastic and can be circular or rectangular.

Q: What is uncontrolled ventilation and why is it important?

A: Uncontrolled ventilation occurs through construction gaps in the external building envelope. It is often referred to as a building's "airtightness". It can contribute to drafts and results in the loss of internal heat gained through heating and occupying the house. Continuous mechanical ventilation is suitable for any level of airtightness.

Q: Can I open the windows?

A: The windows can be opened for comfort control and cooling.