Home ventilation systems – what’s blowing in the wind?

November 3rd, 2011

There’s a lot of talk these days about mechanical home ventilation systems. We’ve seen them on the telly, or on billboards, or our friends have installed one. Opinions about them vary, but in New Zealand they are certainly becoming more common-place. Around 10% of New Zealand homes are now thought to have one.

This seems to be the result of an increased awareness of the importance of having a warm, dry home (something New Zealanders are only just coming to realise is achievable and – gasp! – preferable to what we’re used to), a frustration with living in damp houses (think ‘crying’ windows in winter), and fairly agressive marketing and sales tactics by some suppliers.

Adequate ventilation is vital to keeping your home healthy, controlling temperature and good home maintenance. It removes moisture and pollutants and brings fresh, clean, drier air inside. We spend more than 75% percent of our lives at home, mostly inside so the impact our on our health shouldn’t come as a surprise.

Increased awareness is great because it changes people’s perception of what’s acceptable and normal, but as with many things a little knowledge is not always helpful. We’ve still got a long way to go understanding how to live well in our homes.

You can ventilate your home either ‘passively’ (using doors and windows, or with louvres and vents) or ‘actively’ using some kind of mechanical ventilation system. The most common type in this country are positive pressure systems, the most well recognised brands being DVS and HRV.

If you’re looking at investing in a mechanical ventilation system, the first thing you should ask yourself is what is the problem you’re trying to address? Then you can start to decide what the most appropriate solution is. Is it condensation on your windows in winter? Is it mould in your bathroom or the rooms on the south side of your house? These issues can often be resolved in low/no cost (or subsidised) ways that remove the need for a mechanical solution.

For example, if the issue is condensation there’s either too much moisture in your home or not enough heat. Or both. First thing to consider – what are the sources of moisture in your home and are you giving your home a chance to dry out? Do you have extractor fans in your kitchen and bathroom? Do you use an un-flued gas heater? Do you dry clothes on a rack indoors? Do you have lots of indoor plants? Is it damp under the floor of your home? Are there lots of trees close to your house, shading the light and preventing airflow? Do you open doors and windows when you can to let fresh air in and stale moist air out? 20 questions I know… but all these things influence the amount of moisture in your home, which in turn affect condensation, mould growth and your ability to efficiently heat your house.

The official line from EECA (Energy Efficiency and Conservation Authority) is to “address the source of the moisture problem first, before looking at ventilation systems” something Community Energy Network supports. Once you’ve dealt with the root cause of the issues, then look at a mechanical system if you still need a solution.

If you want personalised advice over the phone, or in your home there are a couple of options. Currently three of Community Energy Network’s member organisations have Energy Advice services. That is, experienced, independent advisors who can talk you through the issues in your own home and help you find solutions. They’re not sales people, they’re there to help you get a better outcome.

You could also contact an Eco Design Advisor. Based in 7 local councils, they provide free, independent advice about sustainable home design and management.

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