There are 4 main strategies for Domestic Ventilation generally adopted in the UK and Ireland.
1. Passive Stack Ventilation
A Passive Stack Ventilation system comprises vents located in 'wet' rooms, connected via near-vertical ducts to ridge or other roof terminals. Warm, moist air is drawn up the ducts by a combination of the stack effect and wind effect. Replacement dry air is drawn into the property via background ventilators (e.g. Brookvent Window Ventilators) located in the habitable rooms, and by air leakage.
2. Intermittent Extract with Background Ventilators
Local extract fans are installed in 'wet' rooms and provide rapid extraction of moisture and other pollutants. They operate intermittently under either occupant or automatic control. The fans can be either mounted in a window, ceiling or external wall. When ceiling-mounted, the extract should be ducted to outside. Replacement dry air is provided via background ventilators (e.g. Brookvent Window Ventilators) and air leakage. In addition, as these fans do not run continuously, the background ventilators should be sized to provide adequate continuous whole house ventilation.
3. Continuous 'Mechanical Extract Ventilation' (MEV) with Background Ventilators
A 'Mechanical Extract Ventilation' (MEV) system continually extracts air from 'wet' rooms. It usually consists of a central ventilation unit positioned in a cupboard or loft space ducted throughout the dwelling to extract air from the wet rooms. The system is typically dual speed, providing low-speed continuous 'trickle' ventilation, and high-speed 'boost' flow. Replacement dry air is drawn into the property via background ventilators (e.g. Brookvent Window Ventilators) located in the habitable rooms, and by air leakage.
4. Continuous Whole House 'Heat Recovery Ventilation' (HRV)
Whole 'House Heat Recovery Ventilation' (HRV) systems usually combine supply and extract ventilation in the one system. Typically, warm, moist air is extracted from 'wet' rooms via a system of ducting and is passed through a heat exchanger before being exhausted to outside. Fresh incoming air is preheated via the exchanger and ducted to the living room and other habitable rooms.
The transition towards airtight, super insulated homes means that purpose-provided ventilation is now more necessary than ever before. England and Wales, Approved Document F , (Ventilation) was revised in 2010 specifically to cater for homes that are completely airtight and which would need larger purpose-provided ventilation openings, with the potential to cause substantial heat loss. For this reason, ventilation options that are able to recover heat from the outgoing ventilation (exhaust) air have an obvious attraction, namely Heat Recovery Ventilation (HRV) systems, which also have the added bonus of offering continuous, demand controlled ventilation which has the ability to respond to levels of increased household pollutants ensuring a comfortable and healthy indoor environment.
A recent detailed report published in February 2012 by the National House-Building Council (NHBC) in conjunction with Building Research Establishment (BRE) supports this view that the current trend towards Heat Recovery Ventilation (HRV) will continue, and suggests that it is likely to become the dominant form of ventilation in new homes to 2016 and beyond.
Below are links to the current regional (UK and Ireland) Ventilation Regulations:
Approved Document F - Ventilation (2010 Edition) Link
Domestic Ventilation Compliance Guide (2010 Edition) Link
Domestic Building Services Compliance Guide (2010 Edition) Link
Technical Handbook 2010 Domestic Link
DOE Technical Booklet K: 1998 - Ventilation Link
Part F Ventilation 2009 Link