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Ventilating and Insulating Roofspaces

"Passing Wind"

Roof spaces are not nice, in fact having crawled around in a few I can quite safely say that they are 'orrible places. This is the forgotten nether world above your head. Roofspaces are always hot, usually very dark and have collected more dust than King Henry's 8th naval (and he's been in his crypt for some time now).

Forget the whitewater rafting, elephant rides or mountain biking, enjoy all the thrills and spills of adventure in your own home, climb into your roof. As you blunder around in the dark trying your hardest not to put your foot through your precious ceiling the adrenilin starts to pump and perspiration starts to run down your forehead and into your eyes where the stinging makes you stumble around like a one legged tightrope walker.

You drop your torch.

“Oh dear” you say politely. Balancing on a piece of wood the size of a matchstick (remember them?) you know you will have to recover the recalcitrant torch. In the dark your hands catch on a tangled mass of something, you can't work out quite what, you carry on groping stirring up the dust which fills your lungs and sticks to the beads of sweat on your face. You start to move faster wanting to get the job done and get out of this terrible place. Eventually you manage to recover the torch and you point it down at the tangled mass of …...... “Oh HHHenry FFFFonda's SSSSShaving CCCCceam” ….. a bundle of electric cables and there in the middle are bare connections, the twisted copper glistening in the torchlight.

For some strange reason it is at about this moment you have had enough “adventure” for one day, in fact all month, and you scurry back across the matchstick beams. In the rush you miss one, there is a sickening sound of cracking and tearing followed by a sudden beam of light from below. You stop, breathing heavily, and carefully struggle to disengage your foot from the hole to reveal a face in the room below staring up at you, the arms are folded and the face does not reflect a sense of compassion and understanding.

She who must be obeyed is very definitely not amused and you haven't broken the edge of the manhole trying to get down yet...........

Your roof space may be a forgotten world but it is worth paying it a bit of attention. The first thing is that if you have a tiled or asbestos roof or, much worse, corrugated iron or pressed steel “tiles” you are living with an oven above your head. The hot tiles heat the roofspace like an oven, it can get very hot, the heat is transferred to the ceiling which in turn heats up the house. You may notice that in some houses you can feel the heat radiating from the ceiling.

In cold climates people are very much aware of insulation and go to great lengths to install double glazing, draft excluders and roof insulation. Unfortunately in hot climates people don't appear to have the same awareness and all too often air conditioners are busy wasting huge amounts of energy trying to cool down the front street.

A starting point in keeping your house cooler and reducing your air conditioning bills is to take two steps:

  1. Install roof vents to ventilate the roof space
  2. Install glass wool insulation above your ceiling.

It is becoming standard practice in Bali to install aluminium foil underneath roof tiles and this is what most people here understand as “roof insulation”. This will have a significant impact in reducing the amount of heat getting into the roofspace. Unfortunately aluminum foil is usually combined with “Triplex” (thin plywood) to support it and this reduces the roof's ability to “breathe” because it prevents breezes from penetrating between the rooftiles.

In Australia, a country with very hot sun and extensive use of corrugated iron for roofing, roof spaces can be hotter than a fire-eater's tonsils but the old bushies learned some tricks. Many of the older houses have what appear to be ornamental circular vents on the ridges of their roofs. In fact these are venturis. They have a vertical chimney with a narrow section in them rather like the flue of a fire. As our parliamentarians prove hot air rises and as the hot air in the roofspace rises through the chimney of the air vent it speeds up to get through the constriction causing suction. These venturi air vents suck air in under the eaves of the house, through the roofspace and out at the top cooling them down and reducing the temperature both of the roofspace and of the ceiling below.

Australian building codes these days stipulate that roofspaces should be vented. Modern roofs don't use venturis but usually have ridgetiles with slots in them. Breezes can pass through these slots drawing hot air from the roofspace below. This works satisfactorily but are no where near as effective as the old venturis which work even in very still conditions.

Look around and you will find that here in Bali most roofspaces are not vented. Change is coming, people are waking up, and you will notice that many roofs, particularly industrial roofs, are starting to sport shiny metal adornments rather like large revolving phallus's on their roofs. These are, of course, air vents. There is no motor involved, they turn simply from the circulation of air through them, they are very low cost and very effective.

Of course most people don't want some great shiny rotating adornment erected on their roof but there are other ways of venting your roofspace. Old traditional buildings sometimes had two tier roofs so that, once again, passing breezes could flow through the gap between the roofs and draw out the warm air from beneath.

With a bit of attention paid to roof design it is a fairly simply matter to incorporate some form of natural self ventilation which will have a significant impact in keeping your house cool.

While you are up in the roof take the time to have a look at your electrical wiring. It should be installed inside plastic conduit (20mm plastic pipe) with junction boxes to protect the cable joints. This conduit is not only to protect the cable from damage or you from touching anything that might be live but it is also to protect the cable from rodents. If you are a true animal lover you will leave tomato ketchup in your roofspace so that those nice little furry tikus grandus (don't worry we all have them) can have sauce with their feast of the insulation on your electric cables. Chewed cable is a very common problem and, of course, can result in short circuits and even fires.

Just take note that if you have an old house be very, very careful. In the past it was common practice to have bare copper wires suspended on insulators to carry the electricity around the roof space. I once climbed into a roofspace to find 3 strands of live copper wire 6 inches from my right hand as I climbed through the manhole. This is very quick way of going through that golden manhole in the sky to the eternal roofspace above. Thankfully there are very few houses still around like this.

Ok you can climb down now, have a shower to get all that dust off you, get the pembantu to call someone to fix the hole in the ceiling and go and book a whitewater rafting trip – it's less exhilarating but much safer.

Copyright © Phil Wilson 2009
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