Smarter Heating & Hot Water

Air Change Rates (ACH)

RoomCategory ACategory BCategory CNotes Lounge/sitting room1.5t1.0*0.5 Living room1.5t1.0*0.5 Breakfast room1.510.5 Dining room1.510.5 Kitchen2.0*1.5*0.5* Family/breakfast room2.0*1.5*0.5 Hall210.5…

Room Category A Category B Category C Notes
Lounge/sitting room 1.5t 1.0* 0.5
Living room 1.5t 1.0* 0.5
Breakfast room 1.5 1 0.5
Dining room 1.5 1 0.5
Kitchen 2.0* 1.5* 0.5*
Family/breakfast room 2.0* 1.5* 0.5
Hall 2 1 0.5
Cloakroom/WC 2.0* 1.5* 1.5*
Toilet 3.0* 1.5* 1.5*
Utility room 3.0* 2.0* 0.5*
Study 1.5 1.5 0.5
Games room 1.5 1 0.5
Bedroom 1 1 0.5
Bedsitting room 1.5 1 0.5
Bedroom, including en suite bathroom 2 1.5 1
Internal room or corridor 0 0 0
Bedroom/study 1.5 1.5 0.5
Landing 2 1 0.5
Bathroom 3.0* 1.5* 0.5*
Shower room 3.0* 1.5* 0.5*
Dressing room 1.5 1 0.5
Store room 1 0.5 0.5

Note:
Category A: Air change rates for older existing buildings (pre-2000). Those with several chimneys and/or subject to preservation orders may require greater infiltration allowance than shown above.
Category B: Air change rates for modern buildings (2000 or later) with double glazing and regulatory minimum insulation.
Category C: New (or existing) buildings constructed after 2006 and complying with all current building regulations.

*Where mechanical extract ventilation is to be installed in a room and the extract volume exceeds the natural infiltration, it is advisable to make due allowance for the air extracted from any connecting room or corridor.

*Where a room contains an open fire or chimney, due ventilation allowance must be made. See section 3.5.4.4.

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