Guide to fans and ventilation

The problems caused by poor ventilation

Stale Air
Stale air can be caused by cooking smells, smoking, odours remaining in the bathroom, a general lack of ventilation around the house as well as a damp atmosphere. saucepan

All these problems cause an avoidable level of discomfort as
well as the risk of respiratory illness and general poor health.

Condensation
Problems occur when steam from the kitchen or bathroom finds relatively cooler surfaces around the house and condenses. Attempts to conserve heat by sealing windows - and therefore reducing natural ventilation - makes this problem even worse.

Condensation can cause considerable problems, from peeling wallpaper and mould growth to severe structural damage such as wood rot and damp.

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Solving the problems

Building Regulations

The Building Regulations Document F1 (1995 Edition) outlines the importance of ventilation and stipulates that mechanical ventilation must be installed in kitchens, bath/shower rooms and toilets.

All fans at www.alertelectrical.com comply with or exceed current Building Regulations and are capable of extracting not less than 60 litres per second from kitchens (See XF150 range) and not less than 15 litres per second from bath/shower rooms (See XF100 range). This means that humidity is removed at source before it can reach the cooler part of the dwelling and cause damage.

Specific requirements of The Building Regulations Document F1 (1995 Edition) on ventilation are as follows:

Bathrooms:
The Regulations require a fan capable of minimum extract capacity of 15 litres per second 54m³hr (32CFM)like the Manrose 4" XF100 range.
Toilets:
The Regulations require a fan capable of at least 3 air changes per hour and with a 15 minute over-run timer like the Manrose 4" XF100 range. N.B. 15 minute over-run is not a requirement in Scotland.
Kitchens:
The Regulations require a fan capable of extracting 60 litres per second 216m³hr (127CFM)like the Manrose 6" XF150 range.
Utility Rooms:
The Regulations require a fan capable of extracting 30 litres per second 108m³hr (63CFM) like the Manrose XF120 5" range.

Sitting the fan correctly

A fan should always be sited in the furthest window or wall from the main source of air replacement to avoid short-circuiting the airflow.

It should be located as high as possible in the window or wall nearest to smells or steam, but not directly above eye-level grills or cooker hoods.

If the room contains a fuel burning device (such as a gas boiler) with a non-balanced flue, it is essential that there is enough replacement air to prevent fumes being drawn down the flue when the fan is extracting to its utmost capacity.
IEE Regulations (U.K.) require that a conventional mains voltage fan in a bathroom or shower must be located where it cannot be touched by a person using the bath or shower and well away from any water spray.

Alternatively, the new Manrose range of 12 volt S.E.L.V. (Safety Extra Low Voltage) fans are specifically designed for the safe ventilation of toilets, bathrooms and shower rooms and can be fitted within the splash area with absolutely no risk of electric shock.

Choosing Manrose fans

REMEMBER:

Axial Fans are designed to move air over short distances, i.e. window fixing or through mounting, and are not suitable for ducting over 2 metres in length. Available in 4", 5", 6" ,9" and 12" sizes.
Centrifugal Fans are designed to move air over longer distances and will perform well against the pressure caused by long lengths of ducting and resistance by grilles. N.B. When ducting vertically it is recommended that a condensation trap is used.
Humidistat Controls Manrose have a complete range of integral Humidistat Controls on all their fans; they are also available with a pullcord override switch. A remote mounted model is also available (1360). All are designed to switch on the fan as the humidity rises in the bathroom and off as it drops. It will continue to monitor the humidity 24 hours per day, thus preventing mould growth on walls and ceilings and drastically reduces condensation problems.

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Types of model

Standard. For remote switching through wall light or separate switch.
Timer model with built-in adjustable time delay operated by the light switch.
Pullcord model with built-in pullcord switch.
Humidity controlled models with built-in adjustable sensor which operates the fan automatically.
P.I.R. model sensitive to movement. Switches on when room is entered and off when room is vacated.

Minimum air changes required per hour

To calculate the correct fan required for a particular room you need to know the room volume in cubic metres, i.e. length x breadth x height, and then multiply by the number of air changes required.

Bathroom & Shower Rooms	3	Conference Rooms	8	Living & Other Domestic Rooms	3	Sports Facilities	6
Bedrooms	2	Garages	6	Meeting Rooms	4	Store Room	3
Cafés	10	Hairdressing Salons	10	Offices	6	Toilets - Domestic	3
Canteens	8	Halls & Landings	3	Restaurants & Bars	6	Toilets - Public	10
Cellars	3	Hospital Rooms	4	School Rooms	2	Utility Rooms	15
Changing Rooms with Showers	15	Laundries & Launderettes	10	Shops	8	Workshops	6

	Example 1	Example 2
Room	Bathroom	Kitchen
Volume	2.0 x 2.0 x 2.0 = 8m³	2.8 x 2.8 x 2.8 22m³
Number of Air Changes Required	3	10
Performance	8 x 3 = 24m³/h	22 x 10 = 220m³/h
Fan Required	XF100T = 85m³/h	WF150MP = 220m³/h

Stale air is also removed by installing the appropriate fan. In certain circumstances, such as in toilets, a timer is incorporated to provide an automatic turn-on period of 15 minutes as stipulated in The Building Regulations.