Domestic Fans & Ducting - Installation Guide

1. As far as possible from the air inlet point to the room, whether this be a supply air grille, window or door. This helps prevent short circuiting of the air flow where fresh incoming air may be extracted in place of the stale air.

2. Whilst giving priority to (1) the extract fan should be sited as close as possible to the main source of moisture e.g. the cooker and sink in the kitchen or the bath and shower in bathrooms, and as high on the wall as is practicable.

3. To prolong motor life avoid installing fans above or close to sources of heat. Extract air temperatures should not exceed 40 degrees C.

4. A fan installed in a bathroom must not be within reach of any person using the bath or shower.

5. For ventilation of shower rooms, it is preferable to use a loft or ceiling void mounted in-line duct fan. This will allow the extract grille to be installed directly above the shower for maximum efficiency whilst maintaining electrical safety with the fan remote from any water spray.

6. Where duct runs from extract fans are routed through cold loft spaces, the duct should be insulated to prevent condensation forming in the duct. Where the duct exits the roof, a weather proof cowl should be fitted to prevent rain entry.

7. Avoid vertical duct runs that allow condensation to run down the duct into the fan. Where a duct is installed from a ceiling mounted fan to a roof terminal form an offset to act as a condensate trap.

8. When installing any extractor fan ensure that there is adequate air leakage into the room to supply replacement fresh air. In tightly sealed homes this may mean the provision of a fresh air grille.

Safety. Do not install extract fans in rooms where open flued appliances are sited.

Fan Selection
To select a fan for any specific location requires the following information:-

Room size (length x width x height) - to calculate the room volume.
Room use - to select the required air change rate.
Fan fixing location (wall, ceiling, ducted) - to finally select the fan type.

Example Room - Fan Type AD10

Shower Size - 2.0 x 2.3 x 2.4
Volume - 11 cubic metres
Fan size - 5 air changes x 11 = 55 cubic metres per hour
Fan fixing - loft mounted with 2 metres duct

Recommended Air Change Rates
Room Use	Air Changes per Hour
Bathrooms and shower rooms	3-8
Bedrooms	2-4
Cafes	10-12
Canteens	8-12
Cellars	3-10
Club rooms	8-10
Conference rooms	7-10
Entrance hall, corridors	3-4
Garages	6-10
Hairdressing salons	10-15
Kitchens (domestic)	10-15
Kitchens (commercial)	20+
Laundries and launderettes	10-15
Living rooms	3-6
Offices	4-6
Restaurants	8-12
School rooms	3-6
Shops	8-10
Shower rooms (sports halls)	10-15
Toilets (domestic)	3-10
Toilets (public)	10-15
Workshop	6-10

Conversions
litres per second	cubic metres per hour	cubic metres per second	cubic feet per minute
1.0	3.57	0.001	2.10

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