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Approved Document F1: 2010 England and Wales (with amendments in 2013) Background Ventilators and Intermittent Fans Building Regulations - System 1

Building Regulations - System 2

Passive Stack Ventilation

Approved Document F1: 2010 England and Wales (with amendments in 2013)

Room

Internal Duct Diameter (mm)

Internal Cross Sectional Area (mm 2 )

Intermittent Extract Rate

Room Kitchen

12,000 12,000 12,000 12,000

125 125 125 125

Kitchen

30 l/sec (adjacent to hob) or 60 l/sec (elsewhere)

Utility Room

Utility Room

30 l/sec 15 l/sec

Bathroom

Bathroom

Sanitary Accommodation

6 l/sec

Sanitary Accommodation

● Mechanical Intermittent Extract Fans located in the wet rooms to extract pollutants quickly at a high rate. ● Can be controlled either: ‑ Manually via integral / remote switch ‑ A utomatically, typically via humidity, C0 2 , motion or other sensors. ● Normally wall or ceiling mounted and ducted direct to outside air using the most economical route. ● Replacement air enters the building via background ventilators, typically in the form of window vents located in the head of window frames.

A PSV System provides continuous ventilation. The driving force being the “stack effect” and the “wind effect”. (Hot air rises and the wind passing over the outlet helps to draw the air out of the building). ● Only need Background Vents in dry rooms. ● Separate ducts must be taken from each wet room. ● Ducts should ideally use no more than one offset (i.e. no more than two bends). ● Offsets should be no more than 45°. ● Placing the outlet terminal at the ridge of the roof is the preferred option. ● If the outlet is more than 0.5 metre from the roof ridge it must extend to at least ridge height.

Domestic Building Services Compliance Guide 2013 edition Referred to in the 2013 edition of Approved Document L1A and the amended version of L1B, Conservation of Fuel and Power.

Mechanical ventilation systems should be designed to minimise electric fan power. The specific fan power (SFP) should not be worse than:

SFP < 0.5 W/L/Sec FOR INTERMITTENT EXTRACT VENTILATION SYSTEMS

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