It pays to be on guard against condensation
WHEN you’re insulating your home, you must be wary of causing condensation problems, says Steve King, from the built environment faculty at University of New South Wales.
“We have very little choice about adopting energy efficiency – we have to use a lot less on heating and cooling than we currently do,” he says. “But one of the consequences of improved insulation standards is that, unless you’re very careful, you can cause significant moisture damage.”
Condensation occurs where humid air hits a cooler surface, like the way droplets appear on the outside of a chilled glass of beer.
In cool climates – which include most of Victoria – your roof or wall cavity can become wet when air from inside the home meets the building wrap, or foil sarking, which is commonly attached outside the frame or under the tiles.
Mr King says Australian homes haven’t been built very airtight or with much insulation – until recently. “Traditionally, while there may have been condensation in homes, it dried out very easily because of the ventilation, so there weren’t any cumulative effects.”
In recent years, he says, New Zealand, Canada and the UK have witnessed widespread condensation troubles after ramping up insulation standards.
“We have to be cautious in making a comparison, because they’re colder climates than most of Australia. But even so, based on their experience, we could be looking at disastrous consequences here,” he says.
Andy Russell, from Proctor Group Australia (which sells insulation and breathable building wrap) was one of the contributors to the handbook.
He says that where condensation forms regularly and doesn’t dry out, it not only causes mould, but can also decay the framing and lining of the house. In some cases, residents will experience the symptoms of “sick building syndrome”, including asthma, itchy eyes and nasal allergies.
Mr Russell advises householders to watch for water stains or mould spots around cornices or skirting boards.
“Stick your head up in the loft first thing on a cold morning,” he says. “That way you’ll see whether it’s a leak in the roof, or if it’s condensation forming on the underside of the sarking.”
To reduce the risk of damp, the condensation handbook suggests using breathable building wraps in cooler climates, rather than the impermeable products now used by the industry. Another smart move, Mr Russell says, is to make sure roof spaces have adequate ventilation that draws replacement air through vents in your eaves or gables, rather than up through the ceiling.
The best strategies for avoiding too much moisture will depend on your climate zone, building materials and the construction method. Whatever the situation, condensation is much easier to avoid upfront than solve afterwards, especially in your walls – it’s very expensive to remove plasterboard or cladding if you think there’s a problem.
Mr King’s key advice is to be aware that condensation is a potential issue in your renovation or building project.
“Don’t be shy,” he says. “Ask your builder quite specifically whether or not there’s a condensation risk with the particular method of insulation being proposed. Ask separately about the systems for the ceiling, walls and the floor.”