Removing ceiling - should I insulate?

Hi Darren
I'd say insulate with batts, the ideal time, slip them onto the battens just before you fix your ceiling. Never going to be as easy again.

I painted my old Zincalume roof with standard white "weathershield", if its white it's heat reflective, no primer. 2 coats. Done it a couple of times over the last ten years.
Last time I used a kitchen broom to brush it on. Saves hire of spray gun and wasted paint, and saves your back. Those corrugated foam rollers are useless.

I'd say the best thing is a couple of 300mm whirlybirds as high up as possible, and maybe a few eaves vents if necessary.

Not one single thing does the complete job, it's a combination I guess.

Cheers
Bill (in Darwin)

Originally Posted by billbeee

Hi Darren
I'd say insulate with batts, the ideal time, slip them onto the battens just before you fix your ceiling. Never going to be as easy again.

I painted my old Zincalume roof with standard white "weathershield", if its white it's heat reflective, no primer. 2 coats. Done it a couple of times over the last ten years.
Last time I used a kitchen broom to brush it on. Saves hire of spray gun and wasted paint, and saves your back. Those corrugated foam rollers are useless.

I'd say the best thing is a couple of 300mm whirlybirds as high up as possible, and maybe a few eaves vents if necessary.

Not one single thing does the complete job, it's a combination I guess.

Cheers
Bill (in Darwin)

thanks Bill, great tips

Originally Posted by ausdesign

I would definitely install a min. of R3.5 batts as you go making sure there are no gaps.
Is there any RFL to the underside of the roofing iron ?
BTW there is an interesting topic on envirotalk on roof venting.

from what I saw there is no RFL on the underside of the roof.

I'll price some R3.5 batts today. any danger with the fibreglass batts? Do you have a preference for type or brand, ausdesign?

Originally Posted by Daren

I'm replacing the ceiling in the lounge, dining, kitchen and hallway and wondering wether I should insulate while Im at it and which method would be best.
?

Leave the old ceilings in place putting battens up and then fixing the new gyprock sheets to these battens. This saves a huge mess and provides some insulation with the air gap between the two. I have done this in three room so far and you cannot notice the small loss of height (although we do have very high ceilings).

Definitely put in insulation but do no use cool and cosy, the previous owners used it here and it is a pain to go into the roof space as well as the stuff falls out of the vents in the ceiling.

Cheers
Rodney

Darren - depends on where you are, if you require minimal heating in winter (i see you are somewhere in qld) then batts directly over the ceiling will not have the effect you want.

Batts in hot environments heat up during the day - they will indeed slow down heat transfer through your roof into the house, but the cost is, that come evening they will continue to hold the heat they collected during the day and re radiate that heat down into the house - so you get cooler days but warmer nights inside the building - btw if you are somewhere like toowoomba that gets cold all this is pointless, but i'll go on anyway....

reflective foil however is very effective at stopping heat coming through a roof, because its radiated heat. the best way of doing this is to install the foil (sisalation) with some air gap between it and the iron of the roof - of course with the ceiling off you will have access to do this to the underside of the rafters with maybe a staple gun.


Windows typically are much the greater in heat gain during the day than roof, and that should be a priority with external shading


the above is even more important in FNQ where batts make buggar all sense at all

Originally Posted by ausdesign

I know this is a sweeping statement and yes if you have large areas of incorrectly orientated glass allowing heat gain and if you don't have good cross flow ventilation then the ceiling batts will work to keep the unwanted heat in once it gets in..

peter, its not about keeping the heat in once its there, its about how the bulk insulation works. at its very basic bulh insulation (batts) only work by providing a layer of still air between the cooler environment and the hotter envirnoment preventing or slowing down as you say the transfer of heat. in a roof space under metal roofing the heat transfer is by radiated heat - radiation isnt absorbed by air at all, and thus its only what the radiated heat hits thats warmed - in this case it is the timber and the batts (or without batts - the ceiling linings). so it is correct to say that batts will help the ingress of heat into the space during the day - absoluetely - as they slow the process of that transferrance down.

However energy transfer is always and will always be a 2 way street.

the bulk insulation does not refect the heat at all, what it does is absorb the heat - thus at night when you have 23c outside, you may have batts sitting directly on your plasterboard at 40c, completely unable to give off their energy any faster than the rate at which they absorbed it - they give off that energy in 2 directions - up and down.

As you rightly say, if its air conditioned then its a different matter. in FNQ thermal mass is often used as a cooler - but it needs to be out of the sun and not heat up - what roof insulation is is a thermal mass, but its in reverse - it heats from above then re rdaiates that heat at night.

prevention of heat entering if thats your primary objective (cooling) is an absolute necessity - especially in climates where the night is cooler than the day

itys potentially argueable that you could stop the overwhelming of the insulation in queensland with R5 or 6 but its far easier (and cheaper) to reflect the radiant heat in the roof in the first place. I didnt make the laws of thermodynamics, but depending on your circumstances its better to work with them than against them

note - if the building has no ventilation and is always closed up, then bulk insulation is clearly best - btw thats how the ratings and rubbish on the greenhouse site are done it would seem - horse for courses