Ventilation in your home is important to maintain air quality and remove moisture. A dry home is generally a warmer and therefore healthier home. As new homes become more airtight the need to add a ventilation system is much greater. So let’s look at the types of ventilation system most commonly available in New Zealand and what they’re best used for.
Positive pressure ventilation systems
These are very common in NZ in existing homes but do not comply with current ventilation standards for new builds. Essentially the system works by taking air from the attic or roof space and pumping it into the main living areas though ducts or vents. The air is trapped at this point and relies on gaps in the building structure to allow it to move. The other downside of these older systems is that they don’t have a heat exchanger like new systems do so they’re not designed to recover heat energy to help pre-warm incoming air.
Balanced pressure heat recovery systems
With newer systems it’s a two-way operation, fresh air comes in and old air is pushed out. It’s also fitted with a heat exchanger that recovers heat energy from the outgoing air and uses it to warm up the incoming air. This system is specifically designed for modern homes with fairly airtight construction and they work best with outlets in multiple rooms so air can flow through the whole house. The performance is also affected by the temperature difference between air inside and out. The larger the difference, the more heat the heat exchanger will recover so if you live in a colder part of the country you’ll see better power bill savings than warmer regions.
Why is outside air better?
It’s MUCH fresher than the air that’s been circulating your house already. Add to that the fact that air from the roof or attic space will be significantly less fresher again. And because there is so little air movment in that part of a home the build up of dust, dirt, mould and insect and rodent droppings makes this air dirty and diffitcult to clean by just filtering it.
Extractor fans and rangehoods
Bathrooms and kitchens generate huge amounts of moisture so a little extra help to get air moving in these rooms is needed. Extractor fans and rangehoods should be placed as close to the moisture source as possible and must be vented to the outside NOT the roof space. And because they only suck air out think about having vents installed across the room from it or slightly opening a door or window in a nearby (but not too close) part of the home to get air moving.
HRV, ERV, HVAC – what’s the difference?
HRV stands for ‘heat recovery ventilation’ and it provides good climate control economically. However, they are mainly just for ventilation. No heating is added so it won’t warm your home (beyond what can be recovered by the heat exchanger). These are one of the best options for Kiwi homes.
ERV stands for ‘energy recovery ventilation.’ Effectively it works the same as an HRV system but an ERV transfers both temperature and moisture and uses it’s heat exchanger to pre-warm the cold air coming in. ERV systems aren’t great in NZ as we have naturally high occurring humidity. ERVs are best for increasing humidty in areas where it is uncomfortably low.
HVAC stands for Heating, Ventilation and Air Conditioning and is much more complicated than the others. Designing an HVAC system design takes mechanical engineering expertise and a grasp of the principles of thermodynamics, fluid mechanics, and heat transfer. HVAC systems are best for offices or large industrial spaces.
Is a heat transfer system also a ventilation system?
While some ventilation systems are combined with heat transfer systems theses days, a heat transfer system on it’s own simply moves around air and heat that’s already in the home, blowing it through ducts or vents. It does not bring new air in and you need to have powerful heat source to make it worthwhile. A heat transfer system is great paired with a wood burner as they generate more heat than is needed for one room.