When you’re insulating your home, you must be wary of causing condensation problems.
When carrying out pre-purchase building inspections on homes built in the last 10 years, it’s quite common to find interstitial condensation in walls and ceilings using a combination of a thermal imaging camera and moisture detection meter. It all comes down to poor building practices and unsuitable wall and ceiling foils that don’t allow our buildings to breathe.
We have very little choice about adopting energy efficiency – we have to use a lot less on heating and cooling than we currently do, 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 – such as Tasmania – 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.
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 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.
In 2011 the Australian Building Codes Board released a handbook on condensation in buildings, as a detailed guide for designers and builders.
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.
My advice is to be aware that condensation is a potential issue in your renovation or building project.
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.
Its important that buildings are constructed tight, however advanced construction materials and informed construction techniques are crucial in effectively addressing potential condensation issues.
It’s also important that blower door tests are carried out at lock up and completion stages of building construction so as to determine if the building is suitably naturally ventilated or if mechanical ventilation will be required.
We can provide advice on breathable wall and roof membranes, energy efficient mechanical ventilation, such as heat recovery ventilation as well as carry out blower door testing for architects, building designers and builders.