Additional insulation on underside of roof - ?

Hi all,
house was built 2 years ago, we have a 2nd floor living space in the "ceiling space" (as it appears from outside) - and have access to the roof space around this.

There is insulation on the external sides of the internal walls in this space - but this area still gets ludicrously hot during summer.

I have installed 2 x solarstars (http://solatube.com.au/roof-ventilation/) and found they made no noticeable difference.

My next thought was to add another layer of insulation - on the "underside" of the roof. It is a colourbond roof, which has a lining of silver material on the underside already (called "sarking" I believe?).

So - to those in the know - would adding another layer of insulation at that location make any difference? and more to the point, does it pose any type of fire risk or contravene and building codes ?

thanks.

I presume this upstairs living space is lined with plasterboard for both the walls and the ceiling so you may have to remove the ceiling lining to install further insulation unless you know what is in there already. Either that or remove the roofing in this area and do the insulating from the top.
It wouldn't contravene any rules - just make sure if you have ceiling lights that you give a bit of space between the insulation and the light fitting for fire prevention.

Stewie

If you remove the plasterboard in order to get access to the voids under the roof framing, you can get an additional insulation boost by replacing the plasterboard (or drywall, as we of the American persuasion call it) with insulated plasterboard. The insulation is a superlight rigid material called aerogel. It adds nothing to the weight of the plasterboard, but a significant amount of R-value. If you have anything piercing the ceiling (down lights, electrical boxes for conventional fixtures, solatubes) you'll need to accommodate the extra thickness. Over here that is done by adding collars to the electrical bits; all the big d-i-y places here sell them, but I don't know about Australia.

There is at least one Australian company that makes the insulated plasterboard, Kingspan. I haven't been able to convince my Australian builder to use it, so we may retrofit our 'colder' ceilings after handover.

Good luck with your project --adding insulation is a really good investment in energy savings and comfort.

Chris

Another good product is foilboard, inexpensive and easy for DIY

sorry I haven't replied properly to this yet, im going to take a photo just to make sure we are all talking about the same thing... i should be able to get to this on the weekend.

Alrighty then - this is a pic of the area - that also shows off my mad photo editing skills and ability to use mspaint to type in clunky text.

yes that's what I thought you meant...

I'd be curious to know what difference it makes

Fibreglass batts held in by more sarking or a more solid type of insulation like foilboard as BE suggests or rigid polystyrene sheets would certainly help keep more heat out of your house. What insulation is in the roof of your upstairs room as opposed to roof space that is visible in your photo?

Stewie

well, the batt's are pretty cheap, but then how much of your heat would come through the wood?

same type of insulation is in the roof of the upstairs rooms.... its meant to be acoustic insulation R3.5 I believe - but I would have to check that in my building docs..... (and even if its in the docs, it doesn't mean the builder actually used what was specified)

as far as the other comment - I would be interested to see how well it works too! but would really prefer to do it once - hence the posting here.

I was thinking insulation batts + soundcheck gyprock.... but batts + foil board (depending on price) could be a good option.

What about using one of the spray on polyurethane foams to add additional insulation? There's a few different brands, and they look fairly easy to apply to the inside of existing roofing. I've got no idea how it compares cost wise..