Thread: Shed Layout Advice

Originally Posted by MaIN2203

...."The shed has three metal purlins (girts ?) along the sides, at the top, middle and just off the bottom. My plan was to attach some 90 x 35 timber studs flat against the purlins as battens and then attach the ply to the timber.....

Hi Mark

I think you have got some more good advice from Moph.

What he and Kingspan do not say is that the foil will act as a vapour barrier and keep condensation to the outside of this barrier.

I am not so sure about his recommendations to use steel Top Hat battens as the steel would act as a heat sink and transfer outside heat direct to the inside cladding. But I do not know enough about the Perth climate to have a firm view. It might come down to a cost decision between top hats and pine studs.

If you decided to go with timber studs, then you could mount the 90x35 pine studs on their narrow edges then this would give you a lot more space for insulation. (90mm stud plus 34mm top hat; Total 124 mm. This would be quite easy to do - just predrill the studs and countersink a 90 mm self tapping screw through the stud into the purlin.

The Australian Government, through the Building Code of Australia, reccomends the following minimum levels of insulation in the ceilings and walls of houses in different cities. I believe that the original recommendations were based on work by the CSIRO. But I am a little puzzled that they should recommend the same levels of insulation for places with such disparate climates.

Insulation Levels.jpg

I wish I had put this much thought into setting up my shed !



Fair Winds

Graeme

Personally I would favour timber batterns over metal top hat. Timber is a better sound insulator and will help with the metal transmission of sound. Another alternative to ply lining would be to use HMR melamine sheets as they are pre finished and will reflect the light.
With you insulation depending on your circumstances you might consider acoustic batts if sound is going to be an issue
Keep in mind that unless you are going to be artificially controlling the internal temperature you won’t experience the level of condensation you might get in a domestic home situation

Ugh, wrote a reply and hit the wrong button.

In brief:

• Don't get too caught up in the nitty gritty of timber vs steel battens if (like me) you also have unshaded windows and an uninsulated roller door with unenclosed gap at the top. Unless you can address major issues like that - and I will try, but it's going to be far from perfect - then there's little point worrying about lesser issues like thermal conductivity differences between wood vs timber battens. My intent is only to (1) keep moisture out and (2) reduce summer heat load to a point where I can reasonably air condition the space when I'm using it.
• Next time it's 35°C+ here, I'll take some thermal images at various points throughout the day to see what the differential between the battens and the insulation is.
• BCA requirements have changed a fair bit since the table that Graeme posted. E.g. BCA 2016 requirements for minimum total ceiling R-value range from R3.1 in the tropics to R6.3 in alpine regions. The provisions of BCA 2019 will come into effect as of May this year and require use of a heat load calculation method that I haven't had reason to get my head around yet.
• Acoustic batts are definitely worth the money IMO. I did some grinding on a steel plate at 9pm the other day. Wifey was working in the kitchen / playroom across the lawn and had no idea that I'd done so.

Don't get me wrong - things like air gap on both sides of the sisalation, thermal conductivity of battens, etc are all valid points for consideration. Just keep in mind the overall structure that you're dealing with, the limitations that apply and the usage you'll be giving it.

Originally Posted by Moph

Acoustic batts are definitely worth the money IMO. I did some grinding on a steel plate at 9pm the other day. Wifey was working in the kitchen / playroom across the lawn and had no idea that I'd done so.

Might I (without trying to hijack the thread) ask if by "Accoustic batts" you mean these or similar please? Bradford SoundScreen, Australia's most trusted acoustic insulation

Originally Posted by Moph

....

• BCA requirements have changed a fair bit since the table that Graeme posted.

......

Are you sure, Moph?

I think that you will find that the figures I quoted are still current for all climate zones for all "very light coloured roofs". As Mark is in Perth I never considered he would paint the roof dark.


Cheers

Graeme

Originally Posted by Midnight Man

Might I (without trying to hijack the thread) ask if by "Accoustic batts" you mean these or similar please?

I used Earthwool R2.0HD 75mm x 600mm acoustic batts. Couldn't tell you what the difference is between the thermal and acoustic batts but they sell both varieties so I assume there is some.

https://www.bunnings.com.au/earthwoo...-pack_p0810598

Originally Posted by GraemeCook

I think that you will find that the figures I quoted are still current for all climate zones for all "very light coloured roofs". As Mark is in Perth I never considered he would paint the roof dark.

Here's the BCA 2016 Volume Two table for light coloured roofs ... varies between R3.1 and R6.3 depending on climate zone:

zMpJjQf.png

i.e. the table you posted showed Darwin & Marble Bar as R4.1 (both CZ1; should be R3.1) and Hobart as R4.1 (CZ7; should be R4.6). The CZ5 locations (Perth & Sydney) and the CZ8 location (Thredbo) were correct as shown.

Originally Posted by Midnight Man

Might I (without trying to hijack the thread) ask if by "Accoustic batts" you mean these or similar please? Bradford SoundScreen, Australia's most trusted acoustic insulation

Feel free to ask away Midnight Man (and any others).... Hopefully we can all learn something.

Temperature is about 3°C higher where the ply is fixed to the metal tophat battens, as compared with the insulated plywood adjacent. Not too terrible IMO.

If you look closely, you can even see small hotspots where the screws are.

IR002577.jpg IR002578.jpg IR002579.jpg
IR002580.jpg IR002581.jpg IR002583.jpg
IR002582.jpg

Originally Posted by GraemeCook

.....The Australian Government, through the Building Code of Australia, reccomends the following minimum levels of insulation in the ceilings and walls of houses in different cities. I believe that the original recommendations were based on work by the CSIRO. But I am a little puzzled that they should recommend the same levels of insulation for places with such disparate climates.

Originally Posted by Moph

.....Here's the BCA 2016 Volume Two table for light coloured roofs ... varies between R3.1 and R6.3 depending on climate zone:

zMpJjQf.png

i.e. the table you posted showed Darwin & Marble Bar as R4.1 (both CZ1; should be R3.1) and Hobart as R4.1 (CZ7; should be R4.6). The CZ5 locations (Perth & Sydney) and the CZ8 location (Thredbo) were correct as shown.

Hi Moph

Thank you for confirming my suspicions.

One government agency providing "expert advice" but not conforming with Australian Standards! Or a typical case of the left hand not knowing what the right hand is doing...


Cheers

Graeme