Ventilation: why fresh air matters

Why fresh air matters in your home

Most of us spend the majority of our time indoors—cooking, showering, sleeping, and simply living. All of these activities release moisture, carbon dioxide (CO₂), and other pollutants into the air. If these build up, they could affect your health and damage your home. 

Many New Zealand homes also have cold spots – around windows, around the edge of the floor or inside the wall. If warm, humid air comes into contact with these cold spots, condensation can form, which can allow mould to grow.  

Surely, I can just open the windows to let some fresh air inside
New Zealand’s Building Code doesn’t currently require homes to have continuous fresh air ventilation. That means many homes rely on open windows
or random air leaks (called "infiltration") to bring in air. But here’s the catch: 

• Drafty homes don’t equal a well-ventilated home 
  Cold drafts through gaps in walls, around windows, or under doors are uncontrolled and inconsistent. They don’t guarantee fresh air—and they can bring in moisture and pollutants from places like roof cavities or wall spaces, negatively impacting the health of your home.
• Open windows aren’t enough. 
  Studies show that relying on windows alone rarely provides enough ventilation to keep indoor air healthy and help prevent condensation and mould. Plus, people often keep windows closed for security, noise, or weather reasons. 
  
  

Won't building a new home mean I don't have to worry about condensation and mould?

Even if you're building a brand-new home, there's no guarantees that your home won't experience condensation and mould, if your house is built to code. That's because your home will be more airtight than an older home, meaning less drafts and moisture coming in from the outside, but moisture from the inside - from showering, cooking, drying clothes - could have a hard time escaping. That is, unless you have some form of continuous ventilation. 

Sick of wiping down your windows every morning, running the dehumidifier, or worse still, cleaning mould off your surfaces?

To keep your home healthy, you need continuous, controlled ventilation—ideally through a mechanical system that runs quietly and cheaply in the background, removing stale air and bringing in fresh air. 

What good ventilation looks like - Balanced Pressure Systems

These are ideal. They use two fans—one to bring in fresh air and one to remove stale air—keeping your home at a neutral pressure. Many systems also recover heat from outgoing air, saving energy and helping to keep your home warm.

 What you can do 

If you’re building or renovating, ask your designer or builder: 

• What kind of ventilation system will be installed? 

• Will it run continuously and quietly? 

• Is the home designed to be airtight? 

• Will the system be tested to make sure it works properly? 

And remember: a healthy home starts with fresh air.