Steam from cooking and showering can be effectively managed by using extractor fans vented to the outdoors and not into the ceiling space. For bathrooms, it's a good idea to put a 10-minute delay timer on your extractor fan.
Moisture coming off of wet clothes and unflued gas heaters is best controlled by avoidance. Put another way, try not to do either if at all possible. Whenever you are able, try to dry your clothes outdoors on the line. If the weather does not cooperate, airing them in a shed or under a deck or waiting for a sunny, windy day would be preferable.
For homes that are built on piles, rising damp can be the largest source of internal moisture by a country mile, accounting for 40-60 litres per day depending on the size of the structure, soil type, drainage, and subfloor ventilation.
Dealing to rising damp can be as easy as laying a ground vapour barrier (aka damp-proof membrane) or - in my case - improving drainage around the perimeter of the structure, increasing subfloor ventilation and then installing a ground vapour barrier.
Over the past six months I have spent hundreds of hours and dollars on all three of these. I finished the work two days before the recent deluge arrived. Ironically, the lowest moisture reading ever recorded inside our home (so far) was the day 88mm of rain fell on our roof.
The combination of drainage work, builder's polythene and more vents has reduced the indoor humidity from a very unhealthy 85 per cent when we arrived to 64 per cent - a level just within what is considered healthy.
Dehumidifiers are brilliant, and we have used one up until recently. It's there at the ready should we need it, but like a positive pressure ventilation system installed in a roof cavity it only removes the damp that is already inside our home.
The following tips come from "Reducing Moisture and Condensation" available free at: http://www.ecodesignadvisor.org.nz.
- Keep beds and furniture at least a hand-width from external walls.
- Wipe condensation from windows as soon as you see it.
- Leave wardrobe doors slightly ajar to allow air circulation.
- Regularly check for mould behind curtains and furniture, and in corners.
- Spray a mixture of 70 per cent white vinegar and 30 per cent water on mouldy surfaces, leave for 15 minutes to an hour, and then scrub. Be sure to rinse off the vinegar afterward with a sponge. This is extremely important as mould will grow back on the vinegar residue if not rinsed properly.
- Wash or dry clean affected curtains.
- If there is no extractor fan in the bathroom, open windows when showering or bathing.
- Flush your home with fresh air once or twice each day for 10 to 20 minutes by opening windows and doors. During winter months the best time to do this is around mid-day when outdoor temperatures are highest. It is better to fully flush the home with fresh air than to leave windows ajar all day and night.
- Only consider a positive pressure or dilution ventilation system as a last resort. They are not suitable for all houses and can cause more problems than they solve.
-Dr Nelson Lebo is an eco design professional specialising in new residential building, renovation, and healthy homes - 022 635 0868; 06 344 5013; theecoschool@gmail.com
