Getting the most out of natural ventilation in your home

Getting the most out of natural ventilation in your home

For many years our homes have sucked.

Literally. Older homes suck air inside via infiltration to naturally ventilate, which for many years was enough. However, newer homes have become more airtight for better temperature control, which is great for energy efficiency, but at the cost of less natural air infiltration and ventilation.

This has led to our homes sucking in a different kind of way. Poorer ventilation leads to uncomfortable living conditions and worse health outcomes. On its own, natural ventilation is insufficient to ventilate a modern home, however, when combined with other ventilation systems you can get the best of both worlds.

But before we get into how you can get the most out of natural ventilation, we should first cover exactly what it is, and how it works.

What is natural ventilation?

Natural ventilation is the oldest form of ventilation. While it now has more to do with opening a window than rolling a boulder away from the mouth of a cave, the principles haven’t changed.

Natural ventilation is simply the process of allowing fresh air to enter and circulate within a space via wind or buoyancy. This is typically done by opening windows, doors, or through natural infiltration (air passing through the natural gaps in a house).

Wind ventilation:

Wind ventilation, or cross ventilation, is the most common type of natural ventilation. As wind blows past a home it creates an area of high pressure on one side, and low on the opposite. Because wind naturally blows from areas of high pressure to low pressure, opening a window on either side of your home will create a pathway for the air to flow through. This air movement helps flush the old, stale air out, ventilating your home.

Buoyancy-driven ventilation:

Buoyancy-driven ventilation is another type of natural ventilation and is more common in larger buildings. This style of ventilation uses the fact that warm air rises, which creates an area of lower pressure around the floor which ‘pulls’ cold air in from outside.



Why is natural ventilation alone Insufficient for homes?

While natural ventilation may be cheap, by itself it is inadequate to meet the needs of modern homes, particularly as they become more airtight. Here's why:

Diligence: One of the biggest problems with natural ventilation is simply that people live busy lives. Airtight modern homes need constant airflow to keep the indoor air quality at healthy levels, which means always remembering to open windows so fresh air can flush the contaminated stale air out. Unfortunately, this is easier said than done, and is why Branz suggests that “Modern lifestyles are not as compatible with the level of diligence required” (IAQ #3, Oct 2019) for natural ventilation.

Noise and Security: Sometimes there are very valid reasons to not want to naturally ventilate a home. Environmental conditions such as medium or high background noise can make your life miserable if you need to rely on having open windows. Security is another concern, if your home has easily accessible windows you may be reluctant to leave their windows open all day with no-one home.

Temperature: Achieving adequate natural ventilation often requires sacrificing indoor temperature. Forgetting to open your windows can turn your home into a hot, humid, stuff box, and opening them for too long can leave you freezing!


But isn’t it cheap?

People often shy away from mechanical ventilation because it isn’t free like natural ventilation, but that isn’t really true. Natural ventilation can have a steep cost, it just isn’t paid up front.

Poor ventilation can lead to extremely costly moisture damage to your home, or health complications for your family. The extra cost of purchasing and running an energy efficient continuous ventilation system is more than worth it for the benefits to your health and home.



Natural ventilation is better WITH mechanical ventilation.

To get the most out of your ventilation system, you should mix natural ventilation with some form of mechanical ventilation, either continuous positive input or continuous extraction.* We recommend you accomplish this mix by using one of the through wall Manrose passive ventilation systems.

The simplest way to explain passive air vents is that they are a hole in the wall that passively allows air (and only air) to pass through. When combined with slow-speed energy efficient continuous extraction fans in wet areas (bathrooms, kitchens, and laundries), these systems negate the main downsides of natural ventilation, the diligence required, as well as lower noise and added security. You can find more information about the passive ventilation systems here:     

So, to get the most out of naturally ventilating passive air inlets you should pair them with an existing ventilation system. For a continuous extraction system, a passive air vent allows fresh air to be drawn in all the way through a home, before being extracted in wet zones. The system works the opposite way with positive input ventilation, allowing channels for the air to flow out of the home.

Unsure about which continuous extraction system to choose? Check out MultiVent for a whole home solution here:



*The New Zealand Building Code requires all home building to have mechanical extraction fans from bathrooms and kitchens – with either low-speed continuous, or high-speed intermittent operation.