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Pro Wired Electrical Contractors and Electricians, Lighting Specialists, Sittingbourne, Kent

Domestic, Commercial and Industrial Electrical Contractors

Call us today 01795 470285


Why We Ventilate

Ventilation is becoming more important in properties due to the nature of the modern airtight buildings. The older style of building introduced natural ventilation through the gaps and cracks in the building fabric. New homes however do not have this type of natural ventilation, meaning they will require some form of ventilation system. The main purpose of ventilation is to remove polluted air from the room/building and replace it with fresh air. Moisture is the most significant pollutant. The ‘average’ family of five people produces approximately 6 litres of moisture per day. This moisture is produced by breathing, bathing, cleaning, cooking, drying clothes indoors, perspiration etc. Moisture not only promotes mould but it can also have unseen effects. The common household dust mite lives in humid environments. The faeces it produces grows fungus upon it where the air is humid. This fungus is prime cause of asthma. Sufficiently high levels of humidity will likely result in mould growth. Other pollutants include carbon monoxide, carbon dioxide, volatile organic compounds, allergens, odours, radon etc. 

Regulations and Guidance

Regulation 7 in The Building Regulations (2000) refers to:

Proper materials and a work like manner. HIS regulation is relevant to all aspects and trades. This means any building work should be done using good quality equipment in a correct fashion, this includes ventilation work. Historically ventilation systems have often been installed by people not competent to do so or those not following the relevant guidance. Several building regulations exist that require consideration when undertaking ventilation work:

  • Approved Document A: Structural Safety
  • Approved Document B: Fire Safety
  • Approved Document J: Combustion appliances and fuel storage Systems
  • Approved Document L1A: Conservation of Fuel and Power - New Dwellings
  • Approved Document M: Access to and Use of Buildings
  • Approved Document F: Ventilation

How these documents are met it up to the contractor. Where air barriers are penetrated, for example through an outside wall, the barrier should be maintained. Ventilation systems should also be able to be used by all persons. This means the height of function switches and sockets should be between 450mm and 1200mm from floor level. All systems require inspection and testing upon completion. It is important that designs are clear, and that the ventilation system is compatible with the other building elements such as, weather tightness fixing of the fan unit and fire stopping. From 1st January 2016 ventilation equipment has been added to the European Energy related Products Directive (ErP). This directive requires labelling on products to show their energy efficiency rating. This encourages manufacturers to design their product on the most energy efficient way possible.

How We Ventilate

When we ventilate, we use energy to move air through the property. There are two main ways in which ventilation uses energy. These are heat loss through ventilation and energy usage through electrical consumption. The greatest energy use is from the continual need to heat the incoming air (dependent on the season) as it replaces the lost air through air leakage. In addition, any form of mechanical ventilation requires electrical power to operate. This electrical consumption is small in comparison to the energy lost in the removal of the warm air from the building. Ventilation systems can therefore save you money in the long run.

Key Terminology

Air Permeability

In ventilation terms air permeability is the definition of how leaky the building is. The lower the air permeability the more airtight the building is.

Specific Fan Power

The amount of power a ventilation system uses in terms of their ability to move air is called specific fan power (SFP)

Background Ventilation

A small ventilation opening designed to provide controllable whole building ventilation (e.g. window trickle vents).

Extract Ventilation

Is the removal of air directly from a space or spaces to the outside. Extract ventilation may be by natural means or by mechanical means (e.g. by an extract fan or central system).

Whole Building Ventilation

Is nominally continuous ventilation of rooms or spaces at a relatively low rate to dilute and remove pollutants and water vapour not removed by operation of extract ventilation as well as supplying outdoor air into the building.

Purge Ventilation

Is manually controlled ventilation of rooms or spaces at a relatively high rate to rapidly dilute pollutants and/or water vapour. Purge ventilation may be provided by natural means (e.g. and open window) or by mechanical means (e.g. a fan).

Ventilation System Types

There are three main ventilation systems.

1. Background ventilators and intermittent extractor fans

A collection of local extract fans in localised areas, comprised of intermittent extract fans in bathrooms, en-suits, utility areas, W/Cs and kitchens (wet rooms) and background ventilators in wet rooms and habitable rooms (non-wet rooms such as a lounge, study, dining room and bedrooms). An intermittent extractor fan is a mechanical ventilator that does not run all of the time, usually only used when pollutants and vapour are required to be removed (e.g. during cooking or bathing). The intermittent operation may be automatically or manually controlled. Background ventilators are small ventilation openings designed to provide controllable whole building ventilation (e.g. window trickle vents).

2. Continuous mechanical extract ventilation

A ventilation system that comprises of either a central ducted continuously running extract fan (centralised) or a set of local continuously running extract fans in the wet rooms (de-centralised), or a combination of both.

3. Continuous mechanical extract with heat recovery (MVHR)

A ventilation system that comprises a central ducted supply and extract fans, air being supplied into the habitable rooms through a heat exchanger. Stale, moist air is extracted from the wet room through extract diffusers; heat from the warm extract air in the wet room is given up to the heat exchanger. Fresh air is supplied to the dwelling through the intake ducts and passed across the heat exchanger, pre-warming the fresh air to ensure the temperature of the dwelling is maintained.

Commissioning of Natural Ventilation Systems

The Building Regulations 2010, Statutory Instrument Part 9, paragraph 42, imposes a requirement that testing, and reporting of mechanical ventilation performance is conducted in accordance with an approved procedure. This is done using a suitable certified measuring instrument, such as the one shown here.

Energy Rating
Continuous mechanical extract ventilation
Continuous mechanical extract with heat recovery
Ventilation system performance testing
Background ventilators and intermittent extractor fans
Pro Wired Electrical Contractors and Electricians, Lighting Specialists, Sittingbourne, Kent

Prowired Electrical Ltd
Unit 12, Precision 4 Business Park,
Styles Close, Sittingbourne,
Kent ME10 3FZ

Tel: 01795 470285
Email us

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