Ventilation is the supply and removal of air by natural and/or mechanical means to and from a space or spaces in a building. It normally comprises a combination of purpose-provided ventilation and infiltration. Considered strategies are vital to ensure healthy homes and compliance.
Purpose-provided Ventilation
Purpose-provided ventilation is that part of controlled ventilation. This can include background ventilators, trickle vents, passive wall vents, extract fans and more complex MVHR systems.
Infiltration
In comparison infiltration is referred to as uncontrolled ventilation. This is exchanges of air between inside a building and the outside, through means of unintended openings in the building envelope, known as air leakage areas such as cracks, porosity, service voids etc. These leakages are caused by pressure difference effects including wind-effects, convection (stack effects).
Whole House Ventilation
Whole house ventilation is normally continuous ventilation of rooms or spaces at a relatively low rate to dilute and remove moisture (humidity/ water vapour) and other pollutants by mechanical extract ventilation, purge ventilation and/or infiltration. By means of extract promotes the supply of outside air into the building through background ventilation.
Wet Room
A wet room is a room used for domestic activities such as cooking, clothes washing and bathing that produce significant amounts of moisture. These specifically include kitchens, utilities, w.c and bathrooms.
Habitable Room
A habitable room is a room used for dwelling purposes but which is not solely a kitchen, utility room, bathroom, basement or sanitary accommodation – as described above as wet rooms.
Types of Ventilation System
Intermittent Extract Ventilation (IEV)
Intermittent extract ventilation (IEV) is a ventilation approach comprising of mechanical extract fans that remove air directly from a space to external air. The extract fans do not run continuously, usually only operable by a fuse-spur or manual control. This intermittent operation allows for a particular need to remove moisture and other pollutants say whilst using a wet room and their associated activities.
Positive Input Ventilation (PIV)
Positive input ventilation is not an approved ventilation strategy. This ventilation approach continuously draws air from outside, passing through a filter and into a dwelling. This creates a positive pressure, pushing moisture and other pollutants out through background ventilation.
Mechanical Extract Ventilation (MEV)
Mechanical extract ventilation is automatic driven ventilation system that continuously extracts indoor air and discharges it externally. This may be a single centralised system with a single exhaust point of a decentralised system (dMEV) where there are a series of independent controlled continuous running extract ventilation units.
Typically these units start to incorporate demand controls such as temperature, humidity and other pollutant triggers which variably control fan speeds.
Mechanical Supply and Extract Ventilation
Mechanical supply and extract ventilation is a mechanically driven ventilation that both continuously supplies outside air to the inside of the dwelling and continuously extracts indoor air and discharges outside. This includes decentralised supply and extract ventilation and mechanical ventilation with heat recovery (MVHR).
An MVHR benefits with a heat exchanger, which runs the incoming unconditioned supply air close to the moisture ladened exhaust air, to allow for heat transfer – essentially pre-heating the incoming air.
Part F Domestic Ventilation Inspection, Commissioning and Air-flow Testing
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