We are often asked by clients about what options there are for ventilation. What would suit a low-energy retrofit, a historic building or a passivhaus building? In this series we’ll explore some common types with infographics and a selection of frequently asked questions.

Q: What is trickle ventilation?

A: Trickle vents are usually mounted within window frames. They can be closed, but for the ventilation strategy to work they should always be left open. They deliver cold, unfiltered 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 trickle ventilation?

A: The calculation can be carried out be the Architect at the Building Regulations stage. There will be requirements for the size of windows and their placement for cross ventilation and this will normally be checked during Planning Stage design development.

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

A: Moist air is typically extracted via an intermittent fan from the wet rooms, utility rooms and the kitchen; and will be exhausted via a duct to the outside. The ducts are typically plastic and can be circular or rectangular. The fan will normally have a 15 minute overrun.

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. Older houses are typically more 'leaky' than modern house so this is a common system in existing homes. However, as homes have become more airtight, to reduce unwanted heat loss, trickle vents do not provide adequate ventilation and can only be used in less airtight homes.

Q: Can I open the windows?

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