New Zealanders have, over the last few years, favoured positive pressure ventilation systems, touted by HRV and DVS products. However, as the style of houses we build evolves, insulation envelopes become tighter, and more housing is built in high-density areas, ventilation and heating needs are changing too.

While positive pressure systems have their place, and provide reasonable performance in certain situations, they are becoming obsolete in many new builds and higher density living situations. As Richard Adams from The Heating Company explains, positive pressure ventilation systems are only valid for older homes that have natural ventilation, not modern air tight homes.

“Positive pressure systems work by pushing warm air from the ceiling cavity into the home creating positive pressure, which then removes moisture from the house. While that is all very well, positive pressure systems take the heat out of the home while removing the moisture, so they are detrimental to your heating costs, which become higher when using this sort of system,” Adams says.

Because positive pressure systems move air from the ceiling cavity into the house, the air is stale rather than fresh air from outside. Also during the winter months, there is only a limited amount of warmth retained in the ceiling cavity so when the temperatures drop, positive pressure systems push cold air from the ceiling into the house.

“As houses become far more airtight than they were even a few years ago with insulation, double glazing and a tighter building envelope, you have to ventilate. If you don’t you end up living in an unhealthy environment.”

And that’s why Adams says specifiers are turning to different solutions and moving away from positive pressure systems that have been favoured of late.
Mechanical Heat Recovery Ventilation systems are far more effective for modern homes and those in high density areas, where windows may not open, Adams says. These systems draw fresh air from outside into the home while extracting pollutant moisture-laden air by passing it through a heat exchanger and returning up to 93 per cent of the energy (heat) back into the home.
“Essentially, you’re retaining the heat you’ve already paid for while removing polluted air at the same time. It greatly assists to keep pollens out of the house, improve the quality of air and help with asthmatics’ health as well as negating grimy surfaces.”
There are two types of heat recovery ventilation systems. The first is a ducted system, which sits in the ceiling cavity. That expels pollutant air through ducting and a heat exchanger outside and is replaced with fresh, clean and warm air to each room. While a ducted system has its place it is generally more expensive to install than the second option because of the need for the extensive ducting. A ducted system also has great challenges when a building is more than one level, has no roof cavity or it is a retrofit situation.

“The other option for heat recovery ventilation is a “decentralised” Mechanical Heat Recovery Ventilation system that sits in the wall cavity of individual rooms. The Heating Company distributes Lunos, a German designed and manufactured decentralised system, which leads the world market.” Adams says.

The Lunos decentralised units sit in the wall cavity, instead of the ceiling cavity, and utilises a ceramic block that retains heat, and a fan system that extracts pollutant air and draws in fresh air, while retaining warmth in the home. “They are 12 volt systems which cost almost nothing to run – about one cent per day per fan.”

The initial cost for a Lunos system ranges between $5,000 and $8,000 which is a very cost effective way to produce a healthy living environment and the minimal operation cost provides a great investment. “This is where the market is headed. You can ventilate and provide a clean, healthy environment for very little ongoing cost. With modern houses, you don’t need to heat as much as you used to, but the need for ventilation is essential.” Mechanical Heat Recovery Ventilation is the best way to achieve this and will provide even greater heating operational savings.

Lunos is designed for modern homes with tight envelopes, and in particular for apartments, townhouses or other small dwellings. The units can also be used in older buildings for the retrofit market, to control moisture levels.

The Lunos system is automated so it will run without needing any manual control. It is also virtually noiseless and is more versatile than a centralised system. “It is simple technology, but it’s state of the art in terms of what it can provide for New Zealand homes in our humid climate.”
The Heating Company has been involved with heating and then ventilation since introducing Hotwire Under Tile Heating system to New Zealand in 1994 and now offers multiple heating and ventilation options.

As our homes change, so too are the needs around ventilation and heating, and the clear move towards the use of different ventilation systems is a step towards ensuring our homes are healthy environments in which to live.