Alternative Technology Assn Forums

1. 

   Frances
   Member

   I am planning for a light weight building in Maleny, which is light weight because of the cost of building on a hill. I am more concerned about winter warmth than summer cooling. The house design makes good use of north and minimise east and west windows etc. I have several queries.
   1. The gov site yourhome says the walls should have a r value of 2.8 minimum, but none of the builders I talk to do this as the norm. Yet they still reach the 6 star standard. How can that be?
   2. I am finding it hard to work out the best way to reach 2,8. If using bulk insulation it has to be kept away from the standard foil, and no one seems to talk about how they are kept apart.
   Any suggestions? Thanks

   Posted Thursday 12 Jun 2014 @ 6:46:46 am from IP #
2. 

   Benny
   Member

   Try this for examples on how to achieve good wall insulation.

   http://www.insulation.com.au/_literature_41669/ICANZ_Handbook

   I think the main idea you will find is to have double thickness walls - not just a 90mm stud. Then you have space for reflective/vapour barrier and bulk insulation.

   Posted Thursday 12 Jun 2014 @ 9:21:34 am from IP #
3. 

   dave lawrence
   Member

   i agree with benny about the double stud walls, but the attachment he included did not illustrate the double stud wall that i thought he was referring to.

   Posted Thursday 12 Jun 2014 @ 8:36:42 pm from IP #
4. 

   tom
   Member

   Maybe consider external foam panels instead of brick. R4 for the panel alone is possible.

   Posted Thursday 12 Jun 2014 @ 9:38:11 pm from IP #
5. 

   dave lawrence
   Member

   if interested pm me and i can send you some details

   Posted Thursday 12 Jun 2014 @ 10:46:57 pm from IP #
6. 

   Frances
   Member

   For some reason I can't get the download to work.
   I understand you can have the frame deeper to allow room for more insulation, but do you need to hold the insulation in place to keep it off the foil? How? Is this extra deep frame plus keeping the bulk insulation in place going to work out very costly?

   It's hard for me to believe that batts will not sag over time, leaving a gap at the top. Doors this happen, do you know?

   Posted Friday 13 Jun 2014 @ 3:23:00 am from IP #
7. 

   Adamc73
   Member

   Frances they use string to keep the insulation from touching the external wall if no wall wrap is used but they never instal it properly. If I was building my own home I would be on site making sure it's done right. Also other trades are the worst offenders in that they pull insulation out to put ducts wires pipes etc and never put it back.

   Posted Saturday 14 Jun 2014 @ 7:43:13 am from IP #
8. 

   Chip
   Member

   Hi - we are about to build a lightweight timber framed house near Canberra and we contemplated having a deeper frame but in the end decided it wasn't cost effective for the extra insulation that could be added.

   Air leakage and expanses of glass (even double glazed) will be the weak link in most houses anyway.

   Starting from the outside we'll have colorbond, 22mm air gap moderately well sealed, reflective foam core insulation wrap, 90mm timber frame with R2.5 batts, another layer of reflective insulation wrap, another 22mm air gap, then plasterboard.

   Total wall thickness inside the slab edge will be almost 150mm and should add up to about R4.0 depending on which wrap we use. Some is up to 12 mm thick and certainly strong enough to keep the batts from bulging to near the cladding. It can offer an effective thermal break which allows metal battens to be used with little penalty.

   If cut carefully, batts won't sag down in the cavity at all. Careful planning of studs and noggings could keep cutting to a minimum anyway

   We will have to figure out whether to use perforated wrap on one or both sides of the frame. Condensation should not be an issue except possibly some occasional harmless moisture on inside of colorbond.

   The air gap behind the plasterboard will be fairly well sealed which will add to effectiveness. The air gap on the outside will be less well sealed.

   Would appreciate any feedback or other ideas.

   Cheers

   Posted Saturday 14 Jun 2014 @ 8:12:49 am from IP #
9. 

   sandystone
   Member

   Cavity battens may be the answer.
   That can provide an air gap of say 19 mm if using timber battens and give you sufficient air gap and also relief from condensation issues.
   There are also proprietary cavity batten systems such as Weathertex or Hardies etc too, though air gaps are less, but address thermal bridging.

   How about this system?- plasterboard + 90 mm studs with bulk insulation + breathable membrane + cavity battens + 15 mm foilboard / foam + cladding (light coloured)

   That would get you over R 2.8

   Posted Sunday 15 Jun 2014 @ 1:41:59 am from IP #
10. 

    Benny
    Member

    Frances have you considered SIPs ?

    Posted Sunday 15 Jun 2014 @ 3:37:38 am from IP #
11. 

    Frances
    Member

    Thanks for all the suggestions. I am unused to these forms so have pmed Benny which therefore the rest of you can't see. Sorry!
    I will look for the foam core insulation wrap, which I hang heard of before

    Posted Tuesday 24 Jun 2014 @ 2:18:45 pm from IP #
12. 

    Frances
    Member

    I have Google foam core insulation wrap without success. I have pmed you, Chip, to ask you where to find it.

    Posted Wednesday 25 Jun 2014 @ 12:49:40 am from IP #
13. 

    Chip
    Member

    Hi Frances,

    There are a couple of different options of the foam core insulation wrap here:

    http://www.greeninsulation.com.au/product-overview/reflecta-break

    Also worth a look is the Pro clima system which uses an airtight wrap either side of the timber frame with batts in it. See http://www.proclima.co.nz/

    We haven't made a final decision on what to use so would welcome any thoughts you have along the way.

    Cheers

    Posted Wednesday 25 Jun 2014 @ 2:59:40 am from IP #

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