Home ventilation

Did you know that, according to Smarter Homes, cooking creates around 3 litres of moisture every day in the average kiwi home? And every time you take a shower, you create another 1.5 litres. Drying washing, doing dishes, even breathing – they all create moisture. Moisture can also get in from damp ground underneath your home. That’s why ventilation is so important – because unless you get rid of that moisture, it can do a lot of damage. 

Excess moisture makes homes colder because it’s harder to heat damp air. It encourages mould and fungi which are bad for our health, and can damage your clothes, your belongings, and your house itself.

There are a number of ways to ventilate your home. They range from simply opening your windows, to installing extractor fans in high moisture areas, up to home ventilation systems for your whole house.

Research from BRANZ found that opening windows fully for 10-15 minutes can provide sufficient ventilation to replace most of the moist air inside a room. It also showed that most of the heat in the walls and furniture was retained – and rooms with dryer air are easier to heat. Getting into a habit of opening windows for 15 minutes in the mornings can make a big difference.

In high-moisture areas like kitchens and bathrooms, windows typically don’t provide enough ventilation on their own. That’s why the healthy homes standards specify extractor fans should be installed in these areas. 

Extractor fans remove or ‘extract’ moist air from your home to the outside. Depending on where they’re installed, they can vent to the outside directly through an external wall or window, or via ducting.

Home ventilation systems which are sometimes also known as continuous mechanical ventilation systems, provide an automated ventilation system for your whole house. There are three main types of home ventilation system. The best type for you will depend on the type, age and condition of your home.

• Positive pressure systems: These bring fresh air in from outside through one or more vents and circulate it throughout the house, which then forces stale, moist air out through gaps and cracks around doors and windows. That’s why they can be a good solution for older homes which tend to have more gaps and places where stale air can escape. Note: some positive pressure systems circulate air from roof cavities, rather than fresh air from outside. However, the air in roof cavities can often be low quality due to pollutants. It’s important you discuss your options with your ventilation provider to ensure they are suitable and refer to the Healthy Homes Standard and building code for more information.
• Negative pressure systems: Continuous, extract only supplemented by window vents may be a cost-effective retrofit option for many homes.
• Balanced or neutral pressure systems: These tend to be used in newer homes and apartments that are more airtight. Like positive pressure systems they bring fresh air in from the outside which is ducted throughout your home, but they also extract stale air to the outside at the same time – so there’s a constant balance of fresh air coming in and moist air going out. Many feature a heat recovery system where outgoing stale air preheats the cooler incoming fresh air (in winter, and the opposite in summer), making heating and air conditioning more efficient.

Another way of reducing moisture in your home is to stop it getting in in the first place. Insulation can help. So can installing a moisture barrier – something as simple as a sheet of heavy polythene under the house.