Do you need a vapour barrier behind wall insulation batts?

[michaeljb]

I'm insulating all the walls. It's single brick . I will use rockwool r2.5 acoustic batts

Do I need a vapor barrier filt behind the batts for extra protection? I do live in melbourne

thanks  

  

[MitchellMc]

Welcome to the Bunnings Workshop community @michaeljb. It's fantastic to have you join us, and many thanks for your question about installing insulation.

It's important to have sarking as it prevents your insulation batts from coming in contact with the bricks and mortar and wicking moisture from them to the timber frame. You can retrofit Ametalin 1370mm x 30m VapourTech Brane VHP Vapour Permeable Wall Insulation between studs. Measure the width between your studs and add 100mm to that. Cut the sarking into strips and use a staple gun to staple 50mm to the side of one stud at the back. Place a staple every 200mm. Transfer across to the next stud and staple it to the side of that one. Repeat this across the span. You'll then be able to install your wall insulation.

Here's an image of how it's done on floor joists, and it will be the same with your wall studs.

Please let me know if you have any questions.

Mitchell
 

[michaeljb]

I did found some information and it says I have to place it next to the internal wall lining? That means I have to also put it in between the gyprock and insulation batts? Ametalin recommended that in colder climates like Melbourne 

Maybe I'm reading it wrong.

[MitchellMc]

I spoke with Ametalin technical support, and I have advised what they suggested, @michaeljb. There was no mention of needing to line between the batt and wall lining. If you can link me to the information you've come across from them, I'd be happy to follow up for qualification.

Mitchell

[NadiaTee]

How does this work with the electricals in the wall? Do you go over it? Under it? 

[MitchellMc]

Welcome to the Bunnings Workshop community @NadiaTee. It's great to have you join us, and many thanks for your question about installing sarking.

That would depend on where the wiring is positioned in the wall. There's no reason why the sarking should go over or under it; the decision would be down to what's easier.

When working around power, it is exceptionally important to ensure any fixings for the sarking do not damage the cable. If in doubt, I recommend you enlist the services of a professional.

Please let me know if you have any questions.

Mitchell