Ventilation for a Healthy Home

Good ventilation in a home is essential to ensure the health and well being of the occupants and to maintain the structural integrity of the property.

Under normal living conditions moisture is generated from internal factors associated with everyday household activities such as breathing, bathing, cooking and cleaning as well as external influences such as rising damp, building leakage, porous roof cavities etc.

Moisture that is not removed from an individual space can appear as condensation on walls or go unseen as dampness in furnishings and building materials and left unchecked will drift into other zones of the home where there is the likelihood of this being absorbed into the internal envelope and furnishings in the balance of the structure.

When moisture is not managed it can:

Affect the health of an individual ( asthma, skin conditions, allergies, sinus problems …)
Damage the physical structure of a building (rotting timber, decaying carpets, mildew damaged drapes...)
Create an uninviting living environment ( musty odors, dampness)
Cool a home down requiring additional heat energy to meet basic health standard levels with not only heating the space but also heating the moisture content in the space
Dampen bedding and clothing directly impacting on the health of an individual. (Mold often appears behind beds close to walls, in fabric items in closet spaces and on carpet close to walls where moisture has accumulated.

Mold growth in the home should not be tolerated because mold physically destroys the building materials on which it grows, mold growth is unsightly and may produce offensive odours and is likely to sensitize and produce allergic responses in allergic individuals. “ Mold will only grow and amplify indoors when there is an adequate supply of moisture”

Homes are built to meet minimum standards where ventilation is to be provided naturally through passive means or if not sufficient then through mechanical assistance.

The building code stipulates that natural ventilation shall be achieved by providing a net opening area of windows or other openings of no less than 5% of the floor space to any given habitable or service area. If the 5% rule cannot be met due to the size of the window or the fact that the space is internal then mechanical extraction is required.

MIN VENTILATION RATES AS PER NZBC G4

Bathrooms	25 l/s
Toilets	25l/s
Laundry	20l/s
Kitchen	50l/s

There are four main zones within a home where specific attention has to be paid;

Habitable Spaces i.e. living areas/bedrooms Natural ventilation or assisted ventilation is required to ensure air changes in spaces for the purpose of providing fresh air to areas and to assist with continuous removal of contaminants in the air to the exterior.

As homes have become more and more air tight with modern construction methods, along with considerations of keeping the home closed up for temperature retention, air quality and security the ability for a house to operate well with unassisted natural ventilation is greatly diminished.

Bathrooms

Bathrooms are one of the major moisture zones within the home with steam and water generated from showering and bathing.

If the moisture is not removed effectively to the exterior it will either accumulate within the space or drift into other areas of the house adding dampness to other zones.

Moisture that accumulates in a bathroom ultimately affects the life cycle of the internal linings, paint finishes and other fixtures with damage such as peeling paint, mold and mildew growth and deterioration of impervious materials. (Mildew mold secretes an enzyme that decomposes organic matter and uses it for growth and reproduction)

The fact that a bathroom meets the standards of natural ventilation with an opening window does not guarantee the space is kept free of moisture and the consequential side effects of this.

Laundries

Laundries are traditionally separate rooms within a home but modern building practices often see laundries placed within smaller closet areas to make best use of valuable space.

The main moisture generator in a laundry is the drier. The building code requires all internal wet areas to be vented directly to the exterior with the ultimate solution being direct ducting of the drier to the outside as well.

If the drier is not directly vented to the exterior the moisture contained within a load of clothes for drying is deposited directly into the immediate space.

It is important with smaller internal laundry spaces that the extraction system installed has the capacity to cope with the Volume of air expelled from the drier with consideration in design of these areas for sufficient replacement air.

Kitchens

All kitchens have a stove or hob that is used for cooking which generates heat, odors and steam as pots and pans are used.

The level of moisture generated from cooking will depend on the number of people living in the home and the cultural cooking habits of the occupants.

If a cooking space is not vented to the exterior the steam and odours will drift into the internal environment.

If a re-circulating range hood is used the odors and grease and fat will be removed but the steam and moisture is still released back into the space.

A range hood ducted to the exterior will remove the odours, grease and moisture directly to the exterior environment.

TO SUMMARIZE, WHY VENTILATE?

Good indoor air quality is a basic requirement to ensure a healthy indoor living environment.
Removing moisture limits the negative effects caused by dampness and maintains structural integrity, therefore minimizing maintenance costs over time.
Avoiding moisture accumulation prevents dampness of internal furnishings, bedding etc which will in turn keep the home and occupants warmer and healthier.
A damp house costs more to heat than a dry house.
Moisture that gets into insulation greatly depreciates the R-Value of the insulating barrier.

Minimizing moisture in the home restricts conditions where dust mites, mold and mildew thrive.