Below is a list of further reading on passive ventilation. This includes both New Zealand literature and also International studies and regulations supporting passive ventilation as an effective means of ventilation your home.
New Zealand Associations
WANZ (Window Association of New Zealand) – Information on Passive Background Ventilation
New Zealand government supported sites, standards, studies and reports
Housing New Zealand – Link to Housing New Zealand’s Healthy housing project, of which we have been a part of for the last five years.
Housing New Zealand have published an Architecture Design Guide.
This lays out the design principles that must be followed on any HNZC development. Page 15 of this document covers the Internal Environment:
Ventilation is required. Due to security issues it is important to provide a means of ventilating houses that is secure. Passive air vents are recommended as people may be reluctant to leave windows open, particularly at night. (4000mm2 of ventilation is recommended to all habitable rooms.)
Passive ventilation grill systems allow the occupant to safely leave an unoccupied house to ventilate. Note: cross-ventilation is needed to meet air change requirements.
Homestar.org.nz – This is the latest website designed to help improve the quality, health and energy efficiency of New Zealand homes.
Damp homes are hard to heat, cause health problems and damage your home. Make sure moisture doesn’t come into your home by fixing leaks and drainage issues and laying a vapour barrier under your floor. Use extraction fans and rangehoods in bathrooms, laundries and kitchens. Regularly air your home – leave windows open or use passive ventilation such as louvres or vents in window frames to bring fresh air inside.
ConsumerBuild – Moisture control and Ventilation – Site developed by the Department of Building and Housing and Consumer NZ
Ideally the air in a home should be ‘renewed’ every two hours, even when you are not at home. Some simple options are to fit aluminium windows with passive air vents or to fit security stays that allow the windows to be left ajar.
Level.org.nz – Passive Ventilation – Level.org.nz is a site developed for the construction industry by BRANZ Ltd, the independent research, testing, consulting and information company.
Passive ventilation is an essential component of passive design and is a free and environmentally friendly method of ventilation that is suitable for most New Zealand locations.
In most New Zealand homes, passive ventilation will be sufficient to meet most temperature control and air quality requirements, so long as it is used in conjunction with localised air extraction systems such as range hoods and bathroom extractor fans to remove moisture and pollutants.
Smarter Homes – Ventilation – Smarter Homes is a a joint initiative by the Department of Building and Housing, the Ministry for the Environment, Consumer, Beacon Pathway Ltd and URS, with assistance from a number of other organisations interested in helping consumers access good quality, reliable and independent information about smart homes.
Good design should strike a balance between the need to introduce fresh, healthy air into your home and the need to maintain comfortable temperatures, so ventilation should be considered alongside passive heating and passive cooling options. If you consider heating without ventilation, you may end up with a home that’s warm but not as healthy or comfortable to live in as it could be.
“Designing Quality Learning Spaces: Ventilation & Indoor Air Quality” – Report developed by BRANZ for the Ministry of Education
“In-home Ventilation Systems” – BRANZ article by Joanna Jackson
“Housing an extended family in New Zealand” – A report by John. M. Gray, Victoria University for CHRANZ (Centre for Housing Research Aotearoa New Zealand)
In very cold or windy conditions, or during the working day when a house is left unoccupied, windows will normally be closed, and stop performing a ventilating function. Contemporary standard window frames are tight-fitting to prevent drafts that commonly occurred in earlier types of timber windows, and they normally lack the means for passive ventilation. The proposed house has passive vents in the frames to provide a trickle of ventilation at all times.
Clause G4 Ventilation (3rd Edition) – Code compliance document for New Zealand Building Code from the Department of Building and Housing. Note: This 3rd edition supersedes the 2nd Edition.
The document sets out the requirement to include trickle ventilators as part of the ventilation solution for household units and accommodation units with only one external wall such as apartments, hotels and motels. This is essential reading for anyone involved in the design of hotel, motel, apartment style buildings.
Under the current G4 requirements (effective from 1 November 2008), the following room layouts must have high level trickle ventilators included in the design:
- Where kitchens, bathrooms or laundries do not have an external wall (section 1.3.3)
- Habitable spaces with an external wall and that are open to a kitchen, bathroom or laundry with a passive stack ventilator (section 1.3.4)
- Habitable spaces with an external wall and no permanent opening to surrounding spaces (section 1.3.5)
- Habitable spaces with both one external wall and a permanent opening to a kitchen, bathroom, toilet or laundry, within which a continuous mechanical extract system is installed (section 1.4.2)
- Habitable spaces with one external wall and a permanent opening to a kitchen, bathroom, laundry, or toilet, within which an intermittent mechanical extract system is installed (section 1.4.3)
The following room layouts must have both high level and low level trickle ventilators:
- Habitable spaces without openings to the exterior, which are ventilated via another adjoining habitable space (section 1.3.6)
The following room layouts may use trickle ventilation to meet the building code:
- Kitchens, bathrooms or laundries that have an external wall (section 1.3.2)
Apartment Ventilation – Proposed acceptable solution G4/AS1 – Report by Sinclair Knight Merz for the Department of Building and Housing
“Hot Air Claim Under Fire” – NZ Herald article questioning the claims of positive pressure systems being heavily marketed in NZ, 21 June 2009
International Standards and Studies on home Ventilation
Approved document F – Ventilation (2006 edition) – UK Building regulations on ventilation
This document specifies one of four methods of ventilation being implemented:
- Passive Stack Ventilation
- Intermittent extract fans with background ventilators
- Mechanical extract ventilation
- Whole house mechanical ventilation with heat recovery
Page 12 of the document includes diagrams of each of these four systems.
Each of the first three options require trickle vents installed as part of the solution to ensure a sufficient flow of outside air to replace the air being extracted. This is more important for modern airtight homes where natural infiltration is below the required level.
The need for background ventilators will depend on the air permeability of the dwelling, and this is not normally known at the design stage. Therefore, as a precaution, it is recommended that controllable background ventilators having a minimum equivalent area of 2500mm2 are fitted in each room, except wet rooms from which air is extracted.
“Energy Efficient ventilation in dwellings – A guide for specifiers (2006 edition)” – UK guide prepared by the Energy Saving Trust / greenspec.co.uk
When installing new windows, the airtightness of the existing dwelling is likely to improve. Unless the room is ventilated adequately by other installed ventilation methods, it is recommended that all replacement windows include trickle ventilators. These allow a controlled amount of ventilation to take place.
This study describes the following typical methods of home ventilation:
- Passive stack ventilation (PSV)
- Intermittent extract fans with background ventilators (trickle vents)
- Single room heat recovery ventilation (SRHRV)
- Mechanical extract ventilation (MEV)
- Whole House mechanical ventilation with heat recovery (MVHR)
Of these solutions, it recommends the use of trickle vents in all but the MVHR option:
Passive Stack Ventilation
A PSV 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. trickle ventilators) located in the habitable rooms, and by air leakage. Providing a gap at the bottom of the internal doors will allow the free passage of air through the property.
Intermittent extract fans and 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. trickle 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. Providing a gap at the bottom of the internal doors will allow the free passage of air through the property.
Single room heat recovery ventilators
As the units are typically only used in wet rooms, appropriately size background ventilators (e.g. trickle ventilators) are required to ventilate the habitable rooms.
Mechanical extract ventilation
Replacement dry air is drawn into the property via background ventilators (e.g. trickle ventilators) located in the habitable rooms, and by air leakage.