Good ventilation can make a home easier to sell. A damp, airless, home can smell bad, which is never a good pulling point for buyers.
Ventilating a home can just mean opening windows and doors to air the house and using traditional or automatic extractor fans in kitchens and bathrooms.
This should always be done before buying a ventilation system, says Christian Hoerning, senior technical adviser buildings at the Energy Efficiency and Conservation Authority (EECA).
If your house is damp, try finding and addressing the source of the moisture before investing in a ventilation system, says Hoerning.
For example if the ground under your house is wet, a ground vapour barrier may be a low-cost way of sorting rising damp.
Nonetheless, fancy ventilation systems do catch buyers' eyes and are an answer for people who don't like opening windows.
Ventilation systems come in two main flavours. There are positive pressure systems and balanced pressure heat recovery systems.
Positive pressure systems are the most common in New Zealand and force filtered air through ceiling vents and into the rooms.
Hoerning says anyone investing in a ventilation system should ensure the air supply is from outside, not the roof cavity, which can be contaminated with mould, rat droppings, or even asbestos.
"Ventilation systems have filters but keeping these clean is often overlooked," he says.
Homeowners can ask for standard systems supplied by most of these companies to take air from outside. But don't assume it will be done if you don't ask.
Balanced pressure systems work best in modern, well-sealed homes, in colder parts of the country.
They supply fresh outdoor air into the house through ceiling vents and a second fan extracts air from the home and discharges it outside after having recovered any heat. Again, make sure the air is coming from outside, not the roof cavity.
Martin Cooper, managing director of Harcourts Cooper & Co on the North Shore, says ventilation systems are listed in sale adverts because they are a pulling point.
"It's always hard to sell a musty, mildewy home," he says. "Smells associated with poor ventilation might even make buyers suspicious that the home is potentially leaky.
"Ventilation systems air the property. We might say to buyers it has beautiful views, the latest Smeg appliances and a ventilation system. It's a value add. It's a definite plus for purchasers."
Smell is one of the senses that makes buyers get a good or bad feeling towards a property, says Cooper, and if it's supplied with clean, fresh, dry air it is going to smell better.
"People say to us they bought a property because it just 'felt right'. It's like popcorn at the movies. It's part of the experience."