Roof Sarking – Dealing with Heat at the Source

Roof sarking to reflect heat

When we hear the word “insulation” we think about different things, and what we think about is usually heavily influenced by our background and our experiences. Most Aussies who haven’t been involved in a building project might automatically think about something yellow or pink, which they’ve spotted being pushed into the walls of a house still in the construction stage. For the home owner-builder or renovator, insulation will mean a whole lot more – it might mean comparing different brands and R-Values, and pricing, and trying to figure out what the house needs and what it can do without, in the way of insulating performance.

There’s no doubt that the word “insulation” carries with it a slightly negative connotation for many older Australians. The fibreglass insulation which was commonly manufactured, imported and installed in Australian homes a few decades ago was frankly horrible to work with, and not wearing gloves and a long sleeve shirt would trigger a persistent itch from the long, piercing needle-like shards of fibreglass. All of the above relates to bulk insulation, but thankfully today, the quality and handling properties of these products has vastly improved, compared to the “olden days”.

Reflective Foil Sarking – A Different Type of Insulation

There is, however, another type of insulation which is altogether different to bulk insulation – it works in a different way and addresses a different type of heat. It is called “reflective” insulation and it is designed and installed to deal with what is commonly referred to as “radiant heat”. Roof sarking is one of the most popular types of reflective insulation, and is a very effective insulator.

One of the best ways to learn how reflective insulation works, or to gain an understanding of its effectiveness, is to crawl up into the roof or loft space of a house which doesn’t have reflective roof sarking installed. If the temperature outside is warm, and the sun is shining onto the roof tiles, unobstructed by cloud cover or any shady trees, then chances are the temperature inside the roof space will be uncomfortably, if not unbearably hot. Why? The main reason is “radiant heat”, and the absence of roof sarking.

Heat Transfer from the Sun and Into the Loft

Think about your typical roofing material – cement tiles or metal sheeting would account for the vast majority of roofs in Australia. These materials share a common trait – they are terrible insulators. Having quickly absorbed the heat energy from the sun, will then immediately commence radiating this heat downwards, into the enclosed roof space. With this in mind, it’s not difficult to understand how a reflective sheet cover such as roof sarking, installed immediately below the roofing materials itself, will make a world of difference to the temperature in the loft space. Sarking reflects the radiant heat back up towards the roof sheet or tile, which in turn, helps to keep the temperature in the roof space cooler throughout the day.

Sisalation roof sarking is effective alone, and is also very effective when installed in combination with bulk insulation batts – the latter which are typically installed between the ceiling joists.

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