# Forum Home Renovation Heating & Cooling  Wall insulation - building wrap under weatherboard

## Aussiejed

Hey all, been a lurker for a while but have reached a point of needing some help. 
Weatherboard house, 40s - 50s construction. Melbourne. 
We're replacing the weatherboards. While the boards are off we thought we would insulate the walls. We're looking at using batts (R1.5 eg Earthwool or something like it). My question regards building wrap. 
The types and use of wrap are confusing. Do we need to maintain an air gap? I've read an air gap is required between foil-sided wraps and the insulation batts but is the air gap also required for non-foil sided wraps? How is the air gap maintained (ie stop batts from moving)?   This is the I've come to an official document but even it is quite vague.

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## Aussiejed

Before anyone says anything yes I did search the forums and found several threads dealing with similar issues, however contradictory advice in those threads. 
As it happens there is a house like ours being renovated professionally around the corner and I snuck a look. I see they've put batts in and then just used the foil wrap over the top. I didn't get close enough to see what kind of air gap they had but it looked like hardly any at all (10mm at most) - which is about what we would get. They do not appear to have battened the weatherboards (which don't look wood) off the studs.

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## Oldsaltoz

Common practice is to add battens the frame before securing the weatherboard to provide a decent gap. 
Good luck and fair winds.   :Smilie:

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## Aussiejed

Thanks for the reply!
I snuck a closer look at the "professional" reno around the corner an found with interest (on the bit they had yet to finish) they had the batts and the wrap with it appears no attention to air gap between.  
Perhaps this is just the "out of sight out of mind" attitude of contractors who figure no owner will be chasing them in 10 years time but... I'd prefer not to set myself up in my own home.  
Sent from my iPhone using Tapatalk

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## goldie1

Batts between the studs then breathable membrane then battens to form the gap then weatherboards  
Don't forget the expansion gaps around the windows ( the ones covered by the architrave )  Use spray foam

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## barney118

I wouldn't worry about battens just use foil with holes used for weatherboard. I don't like the idea of gaps around openings which will let water into the frame.  
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## jimfish

Perforated foil is not recommended for direct contact with timber cladding.
If not using battens you may need to use a membrane like rhino wrap .

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## Oldsaltoz

> Batts between the studs then breathable membrane then battens to form the gap then weatherboards  
> Don't forget the expansion gaps around the windows ( the ones covered by the architrave )  Use spray foam

  Plus 1, for Godlie.

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## barney118

> Perforated foil is not recommended for direct contact with timber cladding.
> If not using battens you may need to use a membrane like rhino wrap .

  "Breather products are pin perforated to allow air flow through
the foil so no excess moisture build up occurs. Breather
products are designed for use on timber or steel frames of
fibre cement and timber clad homes where the cladding is
applied directly to the frame." under suitability page 2

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## shauck

Personally, I'd not bother with battens to an existing building. You will create extra work to deal with window reveal and door frame widths and architraves for these if you batten out. Maybe that's worth the trouble but eh, not so sure. Rhino wrap and clad it.

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## ChocDog

Hey Jimfish and Shauck, 
Which Rhino wrap product do you recommend? I'm guessing Rhino Wrap Breather  RP-51*B*  (the 'breather' version - the high vapour barrier version is just  RP-51). Like Aussijed, I need to do this soon, and dont want to deal  with window reveal issues etc so dont wish to batten out. Shauck I  remember seeing in your thread you did exactly this to your place?   Rhino Wrap | Thor Building Products

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## barney118

i just got some from the green shed

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## shauck

> Hey Jimfish and Shauck, 
> Which Rhino wrap product do you recommend? I'm guessing Rhino Wrap Breather  RP-51*B*  (the 'breather' version - the high vapour barrier version is just  RP-51). Like Aussijed, I need to do this soon, and dont want to deal  with window reveal issues etc so dont wish to batten out. Shauck I  remember seeing in your thread you did exactly this to your place?   Rhino Wrap | Thor Building Products

  I just got whatever the local hardware store had for walls. I was only aware of roofing rhino wrap or wall rhino wrap so up to you.

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## ChocDog

Cheers.

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## phild01

The recommendations here seem fairly confusing.
There are quite a variety of moisture barriers available and in different weights.  Jimfish says not to use breather type with contact with the weatherboards.  Other comment is to use wall wrap and not worry about the contact, but wallwrap is generally the breather type. 
I'd forego the battens as well because of the other difficulties it creates, though agree they would be ideal.  I probably don't think it would matter too much to use the breather type in contact with the weatherboard but maybe it depends how wet the wall might get.  Maybe leave a 25mm gap above the bottomplate.

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## jimfish

The reason I suggested not to use perforated foil is I am currently studying for my cert iv and during the building technology module it was stated that it wasn't recommended for direct contact with timber cladding.
But Barney has shown the manufacturers installation instructions say it's ok so I would think if you follow them it would comply with bca.I will ask the question at school on Thursday night if I remember.
Cheers Jim

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## ChocDog

> I will ask the question at school on Thursday night if I remember.
> Cheers Jim

  That would be much appreciated. It would be good to get some clarity on it. I've also shot a question off to Rhino to see what they say.

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## intertd6

I believe there are some different wall sarking methods depending on the climate zone.
regards inter

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## ringtail

For what it's worth, I have never seen battens spacing the weatherbords off the frame regardless of house style or age. It is definitely never done in new house construction in Brisbane. Frame it, wrap it, batts in, clad it, sheet it.

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## barney118

> The reason I suggested not to use perforated foil is I am currently studying for my cert iv and during the building technology module it was stated that it wasn't recommended for direct contact with timber cladding.
> But Barney has shown the manufacturers installation instructions say it's ok so I would think if you follow them it would comply with bca.I will ask the question at school on Thursday night if I remember.
> Cheers Jim

  You should have done some research first before posting misleading info. BCA only care about R value on sarking not how they are applied.

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## phild01

I have previously read that a gap is required for the foil to achieve the r-rating, that is it apparently doesn't work as well when in contact.

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## shauck

I always thought, as phil01 says, a gap to achieve the R rating but I would think that you can still get some gap without the battens. Isn't that possible by using batts that don't fill the stud cavity too tightly and not pushing them hard up against the weatherboards and sisaltion? This is also why you don't use oversized batts (thicker than the framing materials) in walls or roof Not as good as battens but still... I use a heavy duty staple gun to hold batts in place, flush with the inside edge of the studs. 70mm batts for walls and whatever you can get into the roof depending on rafter thicknesses. I'm not saying this is the best way but it's got to be half way decent if not more.

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