¶ Intermittent fans and passive vents
Extract fans
These typically exhaust air from the kitchen via cooker hoods or bathroom via other independent extractor fans. Extract fans should be included in the 'number of intermittent fans’ category. Those that form part of a whole-dwelling mechanical ventilation system are treated separately, see here and are not counted as extract fans.
Passive stack ventilators
An alternative to extract fans, these are included under ‘intermittent fans and passive vents’ in the ventilation method tab. Such systems typically comprise extract grilles connected to ridge terminals by ducts and should be supplied with air bricks or trickle vents for balancing air ingress. The number of extract grilles in the dwelling should be entered in DEAP.
Trickle vents or air bricks
These alone do not count as passive or background vents and should not be included provided the cumulative minimum open area per room is less than 3500 mm2. If the controllable vents in a room can be closed to less than 3500 mm2 (total), they should not be included as passive or permanent vents. These controllable vents may be manually or automatically controlled.
Permanent vents (including non-controllable trickle vents or background ventilation) of cumulative open area in a room of 3500 mm2 or greater should be counted as passive vents. Permanent vents of smaller cumulative area in a room should not be included in the calculation. For permanent vents associated with chimneys/flues, see here. Permanently blocked vents should be ignored.
Examples:
- One vent in a room of minimum open area 3400 mm2 is not included.
- Two vents in the same room with combined minimum open area of 5000 mm2 are counted as a single vent in DEAP.
- If a tumble dryer is connected to a vent, the vent is not accounted for in DEAP as this is a closable vent.
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Intermittent fans and passive vents examples
DEAP guidance details different types of intermittent fans and passive vents, including controllable vents to be excluded from the DEAP assessment. Several examples are shown below.
Figure 3.1 - Non-controllable wall vent (counted in DEAP subject to guidance)
Figure 3.2 - Controllable/closable wall vent (ignored in DEAP subject to guidance)
Controllable/closable window vent (ignored in DEAP subject to guidance):
Figure 3.3a - Window vent closed:
Figure 3.3b - Window vent open:
Some rooflight windows give the option of background ventilation through use of the opening handle. As this is closable it should not be counted as a background vent in DEAP:
Figure 3.4a - Roof window vent closed:
Figure 3.4b - Roof window vent open:
Permanent wall vents should also be ignored when located in a room containing chimneys, flues and fixed flueless gas fires. For example, in a dwelling with a flueless gas fire and associated permanent wall vents in the same room, the applicable ventilation rate is already calculated by DEAP.
Figure 3.5 - Mechanical extractor fan (cooker hood) counted as an intermittent fan in DEAP
Figure 3.6 - Bathroom mechanical extractor exhaust counted as an intermittent fan in DEAP
Audit example:
- Assessor entered 7 intermittent fans and passive vents in DEAP.
- There were 2 permanent vents, 3 extract fans and 3 closable vents recorded on site.
- The permanent vent in the living area is accounted for by the chimney.
- The closable vents should not be recorded in DEAP.
- Therefore, the entry in DEAP should be 4 intermittent fans and passive vents in the dwelling.