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  1. #1
    Join Date
    May 2003
    Location
    Central Coast, NSW
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    Default Help me interpret our insulation requirements

    Hi. We are building a house and are required to insulate the walls as follows, quoting from our Basix:
    R3 (3.4 including construction)

    My Interpretation of this statement is that counting all the elements of construction from the very inside of the wall to the exterior the total R value must be R3.4.

    We have NRG Greenboard on much of the walls which - looking at the spec sheet and considering our method of construction - gives us the following.

    External air firm R0.03
    Render system. R0.02
    Greenboard 100mm. R2.60
    Sisalation wrap. R0.48
    Cavity and frame. R0.17
    10mm plasterboard. R0.06
    Internal air film. R0.12

    Giving total value of R3.48

    At first sight, this seems to mean we have hit the required R value. Is this correct ?

    Second question. Insulation is relatively cheap, and we have very large walls facing west with no eaves. Is there any value in upping the R value by, perhaps, putting some R1.5 or R2.0 batts into these walls. Will it make the walls perform better and will we be more comfortable? Or is there some reason it may have a negative effect or no effect at all?

    Cheers
    Arron
    Apologies for unnoticed autocomplete errors.

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  3. #2
    Join Date
    Apr 2018
    Location
    Nsw
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    64
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    Default

    Regardless of your target R rating I would be putting batts in your frame as it is the closest element to your interior and good value for money
    You may even consider acoustic batts if you have a potential noise issue, I also like to put them in internal common walls between bedrooms or backing onto a washing machine etc

  4. #3
    Join Date
    Jan 2003
    Location
    Osaka
    Posts
    909

    Default

    Quote Originally Posted by Arron View Post
    Second question. Insulation is relatively cheap, and we have very large walls facing west with no eaves. Is there any value in upping the R value by, perhaps, putting some R1.5 or R2.0 batts into these walls. Will it make the walls perform better and will we be more comfortable?
    Dear Dog, yes!

    Western facing walls soak heat from the sun and radiate it into your living space. Do it.
    Semtex fixes all

  5. #4
    Join Date
    May 2012
    Location
    Woodstock (Cowra)
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    74
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    3,381

    Default

    Do it!!
    Make sure you use the appropriate breathable sarking or you could end up with mildew problems
    The person who never made a mistake never made anything

    Cheers
    Ray

  6. #5
    Join Date
    May 2003
    Location
    Central Coast, NSW
    Posts
    3,330

    Default

    Thanks for the replies guys. I expected that more is better but was mainly just checking to make sure there were no issues that might arise that I hadn’t considered, especially wrt moisture issues.

    How about my first question ? Any answers to whether I have hit the appropriate R level (leaving aside the fact that as I have the opportunity to exceed it then I definitely should)?

    Cheers
    Arron
    Apologies for unnoticed autocomplete errors.

  7. #6
    Join Date
    Feb 2015
    Location
    Hobart
    Age
    77
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    649

    Default

    Quote Originally Posted by Beardy View Post
    Regardless of your target R rating I would be putting batts in your frame as it is the closest element to your interior and good value for money
    You may even consider acoustic batts if you have a potential noise issue, I also like to put them in internal common walls between bedrooms or backing onto a washing machine etc
    Yes to acoustic batts. We didn't have any installed in the walls of our bath and shower rooms. It is amazing how much the sound an unfurling roll of loo paper gets amplified in the cavity of the walls... DAMHIK !!!

  8. #7
    Join Date
    Apr 2013
    Location
    Macksville
    Age
    62
    Posts
    391

    Default

    When I was doing energy efficient building design, as part of a TAFE course I was doing, we were told that to keep heat in, in a cold climate, use bulk insulation (batts) & to keep heat out in hot climates use reflective insulation. Batts insulate by absorbing the heat, which will radiate into the house at night. I used something similar to these Concertina Foil Batts | Going Solar in the west facing walls of our last house & it made a huge difference. I stapled them to the wall studs when I renovated the kitchen & dinning room.

  9. #8
    Join Date
    Feb 2015
    Location
    Hobart
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    77
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    Default

    Are these Concertina Foil batts used together with or without insulation batts?

    Cheers Yvan

  10. #9
    Join Date
    Apr 2013
    Location
    Macksville
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    Default

    Quote Originally Posted by yvan View Post
    Are these Concertina Foil batts used together with or without insulation batts?

    Cheers Yvan
    Without, they need an air gap either side to work. If you go down the page in the link I posted to the section on using them in walls, it explains it all.

  11. #10
    Join Date
    Jun 2011
    Location
    Melbourne, Australia
    Posts
    32

    Default

    Quote Originally Posted by rwbuild View Post
    Do it!!
    Make sure you use the appropriate breathable sarking or you could end up with mildew problems
    +1

    As dwellings have come to incorporate higher levels of insulation and become more airtight, the problem of moisture accumulation from condensation has increasingly raised its ugly head. One-way breathable sarking (vapour permeable construction fabric) is specifically designed to mitigate this problem.

    BTW, whilst the law of diminishing returns applies (say, R5.48 versus R3.48), insulation is relatively cheap and effective for the life of the building. Make sure bulk insulation is installed with its uncompressed width retained so far as possible and with a minimum of gaps around building elements and services such as plumbing, electrical wiring etc. Gaps in insulation in particular will lead to a disproportionate reduction in overall performance.

    Cheers

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