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Ventilation – A Guide to Fans and Ventilation Problems

Visit Our Fans and Ventilation Section to View Our Product Range

Mould and Condensation Problems

Condensation Problems

Steam is constantly being produced in your home, such as steam from a hot bath or shower in the bathroom, or steam from cooking in the kitchen. This steam finds its way to cooler surfaces around the house, in particular windows, and condenses (turns back to a liquid form).

It is common for households to try to conserve heat by sealing windows, reducing natural ventilation, which only adds to the problem as the steam can’t escape from the house.

 

           

Mould

Condensation can lead to very significant problems, from peeling wallpaper right through to mould and mildew, or even severe structural damage such as damp or wood rot that can be extremely expensive to repair.

          

 

Stale Air

Poor ventilation also means that oxygen is not being circulated through the air in your home, carrying odours away with it and creating a fresher atmosphere. Cooking smells, smoking and other odours all add to the problem if the house is not well ventilated enough.

Stale air is not just unpleasant to breathe – it also carries the risk of respiratory illness and general poor health.

 
Solving Poor Ventilation Problems

The Building Regulations Document F1 (1995 Edition) places emphasis on the importance of good ventilation, stating that some form of mechanical ventilation must be in place in kitchens and bathrooms, including a toilet or shower room. The regulations give the following specific requirements:

Bathrooms – fan must be capable of extracting at least 15 litres per second

Toilets – fan must be capable of at least 3 air changes per hour and (except in Scotland) with a 15 minute over-run timer

Kitchens – fan must be capable of extracting at least 60 litres per second

All of our fans such as Manrose fans and Airflow extractor fans meet or exceed these specifications.

How to Install Fans

It is important to think about how to position fans for the best ventilation effect.

A fan should be located:

·         As high as possible in the wall or window nearest the source of steam / odours

·         NOT directly above eye-level grills or cooker hoods

·         In the wall or window furthest from the main source of air replacement (to avoid short-circuiting airflow)

 

          

If there is a fuel-burning device such as a gas boiler with a non-balanced flue in the room you wish to install the fan in, you must ensure that there is enough replacement air to prevent fumes being drawn down the flue when the fan is extracting at maximum capacity.

According to IEE Regulations in the UK, it is also essential that a mains voltage fan in the bathroom or shower room must be positioned where it can’t be reached by someone using the bath or shower, and far from the water spray.

However, our 12V fans  are extra low voltage and specifically designed to be safe for use in toilets, bathrooms and shower rooms. These fans can be fitting within the splash area with absolutely no risk of electric shock.

 

Choosing The Right Fan

Choose the right fan for your needs to ensure optimal ventilation:

·         Axial Fans – these are designed to circulate air over a short distance only, such as through a window fixing, and are not suitable for ducting that is more than 2 metres in length. They are available in 4”, 5”, 6”, 9” and 12” sizes

·         Centrifugal Fans – these are designed to move air over a longer distance, performing well against the pressure caused by long ducting or resistance to grilles. Please note that when ducting vertically it is recommended to use a condensation trap.

Both Manrose and Airflow offer humidistat control options on their fans, or you can opt for a pull cord override switch. A remote humidistat is also available.

Humidistat controls are designed to monitor humidity levels in the room 24 hours a day, switching the fan on as the humidity rises, and off as it drops. This drastically reduces condensation problems and prevents mould growth.

Types of Model

·         Standard – switched on/off remotely through a switch, either its own switch or at the same time a light if switched on/off

·         Timer – built-in adjustable time delay operated by the light switch, e.g. automatically turns on for 15 minutes when   the light is switched on

·         Pull Cord – built-in pull cord switch

·         Humidity Controlled – built-in, adjustable sensor to operate the fan automatically as and when needed

·         PIR – built-in motion sensor that switches on when someone enters the room and off when they leave

 
Minimum Air Changes Required Per Hour

For optimum ventilation, use the table below to calculate the correct fan required. You will need to know the room volume (length x breadth x height) and then multiply it by the minimum number of air changes required (shown)...

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