I spent all of last weekend crawling around in our attic, cleaning out 70 years of dust and laying insulation batts. Total project cost (batts, tools, safety equipment) was $570 for an 82sqm ceiling.
By far the hardest part was removing all the dust from the attic. Our tiled roof does not have any sarking installed, which increased the amount of crap that is able to find its way in. Worst of all, our original ceiling is lath and plaster, resulting in a concrete ridge every few centimetres creating nice little gathering spots for dirt. It’s worth noting that this ceiling dust is nasty stuff, full of lead and other contaminants so you may like to consider a professional cleaning service. (I’ve heard this costs about $1,500AUD and is probably the route I’d take if I ever have to do this again in my life now that I’ve proven my stupidity.)
First, I tried using our household vacuum cleaner. After only a few square metres the bag was full and the machine would overheat. Cooling it back down in the attic environment was difficult, making this a slow process.
Second, getting more desperate, I tried our outdoor blower / vacuum. Predictably, and not as spectacularly as I expected, it was only able to pickup a small amount of the gunk which it then promptly spewed back into the air through it’s course filters.
I then spoke with Kennards about hiring an industrial vacuum ($68/day), which I’m sure would have worked well and is the solution a number of my friends took. (I would have done this earlier, but picking up an industrial vacuum is non-trivial when you don’t own a car.) Unfortunately, we have an unusually small manhole that the vacuum would not fit through. I considered removing roof tiles and battens, but this seemed like a high risk strategy particularly with forecasts of rain on the weekend.
So, in the end, I spent a day and a half removing many kilos of dust from the attic using a dustpan and broom on my hands and knees. I refined the process down to brushing along each 2cm x 40cm plaster crevice towards the beam, and then lengthways along the beam. This gathered the most dust and piled it for an easier lengthways brushing over the plaster ridges.
All in all, brushing was reasonably effective, but is definitely not recommended.
Compared to cleaning out all the crap, laying the actual insulation batts is fast and easy. I settled on Bradford Gold R3.5 batts, which were not at strong as the R4.0 I wanted, but were immediately available off the shelf at Bunnings.
Understanding as much as I could about R-values, it appears that the typical recommendation in Sydney is R3.0. The primary problem in our house is loss of heat during winter combined with 12’ ceilings, so I wanted as much protection as possible. In Sydney, we have a habit of believing we live in a warmer climate than reality suggests (hence no central heating and constant comments of “I should have brought a jumper”). BTW, don’t be confused when the US uses imperial R-values rather than metric R-values. R3.5 (metric) is approximately R20 (imperial).
The one area I still don’t understand is the use of vapour barriers with bulk insulation batts. I know that the vapour barrier is important to stop the build up of condensation. I know that it should go on the warm side of the insulation layer. But, I could never work out if I need a vapour barrier in simple pitched roof with batts on the flat ceiling. I couldn’t find any instructions for vapour barrier installation in this scenario and in the end, it appears to be something people worry about more in environments with an extreme difference between inside and outside temperatures than they do in a Sydney style location. So, I didn’t install a vapour barrier.
There are 4 things you need to know when buying batts: desired R-value, gap between your beams (450mm centres or 600mm centres), total sqm to be covered and how the hell you are going to get all these massive bags back to your house. The beam gap is easily measured in the ceiling and the total sqm can be estimated from ground floor level. I’d definitely suggest buying extra batts, so you can shove them in around the edges and not be stuck in the roof covered in crap wishing you’d had just one more bag delivered.
Delivery of the batts is an obvious choice, particularly when without a car the alternative is to pile them into a taxi or walk them home bag by bag. Unfortunately, on this particular night at this particular Bunnings the task was all a bit much. We got there, but only after they (impressively) called in the store expert from his holidays to help with the computer. $35 for a huge pile of batts delivered next day delivery after 4pm.
Opening a packet of batts is like pulling the cord on an inflatable raft. In one of the few home handyman lessons my father has passed down, I didn’t make his error of opening them inside a small bathroom before taking the pack into the ceiling. But, our tiny manhole struck again as I squeezed, pulled and wobbled 10 packs through.
Laying the majority of your batts is dead simple. They fit perfectly between the beams and are fairly easy to throw around. Even with the recommended face mask and overalls I ended up fairly itchy on my arms, so be sure to invest the $20 in this gear. The only slight complication is making sure that you don’t cover all the electrical wiring, I just loosened any fasteners and laid it across the top of the batts.
Batts around the edges require some trimming. I bought a retractable knife which worked OK until I woke up to the idea of cutting them with a beam as the “chopping board” at which point it worked brilliantly. Our roof has a fairly high pitch, so even laying in the corners was not too difficult.
Basically, with some preparation (i.e. buy batts & safety gear) and a little determination you should be able to completely clean and insulate your ceiling in a weekend.
One week later I’m finally able to kneel down again. More importantly, over the 40C weekend our house stayed cool during the day (great) and then relatively hot at night (not so great, but proves the effectiveness of the insulation).