Wednesday, August 19, 2009

RENOVATION FIX: Beware of sarking and insulation problems

I applaud ceiling insulation as one of the easiest ways homeowners can reduce their energy bills and make their home a more comfortable temperature all year round. BUT there is a problem with high levels of insulation and what's known as sarking - a reflective foil installed underneath roofing material like tiles or colorbond. You see, if a roof cavity isn't well ventilated and ceiling batts are laid on the floor of that roof cavity then the entire space can turn into a condensation chamber. See that image above? Well, sarking acts like the edge of the glass and if it doesn't breathe or ventilate to the outdoors then the temperature differences can create condensation within the roof cavity. This picture shows some of the droplets along the roofing timbers that can be seen in most homes that have insulation and sarking.
The big problems with condensation often don't make themselves obvious, but include:
1. The water creates a mould-growing environment
2. Moisture appears on the ceiling below, but many think it is a roof leak
3. The south-eastern corner of the house (the least ventilated with little sunlight) can become mouldy
4. The mould can lead to sick building syndrome, where the home occupants are breathing in bad air which can lead to respiratory problems such as asthma.
So what's the solution?
- ensure the roof cavity is ventilated, perhaps with a whirly bird
- if building from new, use breathable sarking rather than solid sarking which allows the moist air to escape
- if the insulation has become soaked and is mouldy, it must be removed and replaced.
With the governments $1600 insulation rebate happening, it's the perfect time for people to be reminded that this CAN be a problem ... but don't let it stop you installing the wondrous insulation material. Any insulation is better than none.
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Pictures: Diagram by Kieding,

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