Insulation coverage - impact on effectiveness.

Gentlefolk,

Looking for some advice on ceiling insulation for PPOR.

PPOR is a 1930's weatherboard with absolutely no insulation. Majority of the home has 3.0m ceilings except for an addition right across the back of the house with 2.3m ceilings. Main residence is gable roofed, with a tiled skillion roof to the rear. Rear of the house faces due west with no shade. Approximately 2/3 of the addition is separated from main house by plasterboard wall, with the remaining third an open archway. Plan is to extend out the back in 12-18 months to add a kitchen/family and a bedroom.

Have had 3 quotes for r5.0 insulation supply and install. 2 at approx $1500, both excluding the skillion area due to lack of access. 3rd quote is approx $2K, which includes removing roof tiles from skillion and insulating both skillion area and the wall over the arch (between the two ceiling levels).

My thinking is that not insulating the skillion area will significantly impact the performance of the insulation (particularly during summer). The two cheaper installers say it won't make much difference, which I don't believe. On the other hand, paying to install an area earmarked for demolition seems wasteful...but so does only doing half the job.

Does anyone have any experience they can offer in this area?

Cheers,
Scott

 

How big is the space between the skillion ceiling and the roof?

Just squeezing insulation into a skillion isn't necessarily that effective. If batts touch the roof, some of the insulation value can be lost - and you may not have enough room for foil as well.

I would leave it, if you are renovating. It would be wasteful if it's going to be pulled down.

In the meantime, use external blinds and sunblock internal curtains to reduce the effect of the western sun, and a thick curtain across the archway.

 

Thanks for the reply Joynz.

Wouldn't the cost of external blinds, sunblock curtains and a thick internal curtain consume most of the $500 saved on insulation?

Floorplan is somewhat disjointed, with the kitchen being partially in the main house and part under the skillion. The arch is 'mid-Kitchen' and the toilet is also under the skillion accessed via the kitchen, so the heavy curtain to block off the arch would be unworkable...hence why I question the impact of not insulating the skillion area.

I guess the real question is whether insulating the main part of the house (bedrooms, bathroom, lounge) would be of benefit if the skillion is not done?

From a theoretical perspective, the higher ceilings of the uninsulated part would likely suck heat from the skillion. Given the skillion is also a high use area (kitchen and toilet) I am concerned that not insulating it could mean the remaining insulation is ineffective and therefore also wasted.

Cheers,
Scott

 

Curtains and rods are not expensive, $150 (from memory) for nice curtains on a big sliding door, Bunnings have curtains cheap.

DIY! DIY!

Sliding roof tiles up is easy (just make sure you can get spares from a renovator junkyard), Bunnings has insulation and crawling around the roof space is no drama, wear long longs and a P2 mask, lay it in and cut it away from lights and fans in the roof space.

 

I would just do the main house. Sure it is only half a job, but the other half will be done when you demolish the back section and extend.

As well as the insulation, add whirlybirds on the roof and big vents under the eaves to maximise air flow in the roof cavity.
Marg

 

Funnily enough I was just looking at solar powered extraction fans. Not really that much more expensive given their capacity is much greater.

 

Switches off at night.

 

So I won't have to worry about any noise interrupting my rest

 

Just make sure you install the large eave vents. Many installers don't mention them, and for hot air to be extracted efficiently from the roof cavity you need a separate means of fresh air entering.
Marg

 

Thanks for the tip.

And before someone jumps in, yes I know it will be sucking in ambient temperature air but that's a lot cooler than the air trapped in the roof cavity!

 

Not much fun on hot nights though. In all seriousness, I can't hear any noise from whirly birds I have seen installed.