GraemeS

Hi All,
We have insulation R3.5 batts in our roof (glass wool type) - its still pretty cold during the night here in Perth.

We are thinking of doubling the insulation up so its twice the thickness by laying another lot on top.

I think this is going to help in the winter, but how much extra heat will be likely when summer comes back?

Japonica

If I recall (from some of the helpful threads on here), you'd need to have joists that were adequately spaced to begin with (450mm vs 600mm standard--from memory, correct if I'm wrong) to support the extra insulation.

I'm curious about this too...I'm thinking about adding extra (we're building), and I saw an ad talking about "reduce your carbon footprint blah blah blah....add extra roof insulation, cooler in summer" but wondering how it won't just trap more heat in the house...

MrCro

speaking as a builder the additional rolls of insulation should be laid at 90o to the existing insulation between joists so it should not be an issue what centres the joists are spaced at? The weight of insulation rolls is negligable here in UK so extra weight not an issue (unsure about Oz insulation types and weights tho.)

In regards to summer it does help keep cool as the roof space of a house in summer with the sun heating the roof (especially with darker roof tiles) gets suprisingly hot. Some of that heat is transferred through ceilings but less so with increased roof insulation so yes it should keep coller.

Also cool air from air con is retained longer in better insulated houses so air con costs should decrease.

Siren & Brian

I would focus on windows and doors first.

KRudd has just added extra batts to our home and done little.

Dorothy

Yeah, I can't see that roof insulation would do much when the windows are single pane and the walls are uninsulated. Double brick with no insulation when it gets down to single digits over winter is just stupid.

Wol

If you lay more insulation over what's there you will have big problems stepping around in the loft, not being able to see where the joists are!

Friend of mine has just had his laundry ceiling redone after putting his legs through while investigating why his gas heating wasn't working after our gas outage last week (and he hasn't *any* insulation!)

Japonica

Yeah, that bugs me too but I can't see an economical way around it...ideas anyone?

ozhappy981

Yes, the OP needs to have the joists spaced at 400mm and the gyprock ceiling needs to be a minimum of 10mm.

We have R6.0 in our house and I got the above instructions straight from the horse' mouth: The Bradford Insulation technical helpline.

But if the OP has already got R3.5, I would look at double-glazing and cavity wall insulation first before adding more to the ceilings.

We used Perth Double Glazing (they are based in Rockingham) and are very happy with their work: www.perthdoubleglazing.com.au

GraemeS

Thanks for the comments - just been to Bunnings (B&Q), didn't buy anything yet.

Dorothy

I'm going to stock up on the 3M window films when I'm over in Canada in July. Crappy Tire does their own brand for about 1/2 the price so I plan to bring home a whole whack of them. Other than that about the only thing I can think of for wall insulation would be if you could find someone who would do the cellulose insulation and get that done. It would have to be sprayed in via either holes drilled in the interior brick (between the interior and exterior bricks) or from the roof space where the roof meets the top of the brickwork.

Wol

I would be VERY careful about filling a cavity wall. The cavity is there for a reason, and even so-called waterresistant fills can allow condensation to cross by capillary action and make the interior skin damp.

Dorothy

Yeah you're probably right. In NA we used to have vapour barriers between the exterior walls and insulation. I never thought of that here.

Japonica

I was just thinking about that today...I was reading online and it said something about water-resistant insulation, but what would that be here? I'd imagine most insulation here without vapour barriers is going to be one soggy mess...and moldy...

I swear the insulation issues here drive me bonkers...this is one place that could sure use it for a number of reasons, but they don't make it easy...

Dorothy

It would cut down so much on the need for air con if the houses were properly insulated. Oh well. At least I'm bringing home the window film.

johnandjoanne

we are coming out in September as pr,s, i know it can get a bit chilly at times so as much as everyone has told me "you must be mad"we are bringing our wood burner, the question is " am i mad" !!!!