Alternative Technology Assn Forums

1. 

   bennygsr
   Member

   Thanks for this forum - a great source of information. Short time lurker, first time poster: I tried Whirlpool forums, but no response to my very specific question as yet.

   We are renovating our house and the amount of options and variety in insulation options is hard to work through. I've read the very useful yourhome.gov section on insulation and passive design now numerous times.

   The new section of roof is colorbond (light colour) and relatively flat fall, with a shallow roof space (about 500mm). The roof will get anticon underneath, then have some air space and I'll put large bats in above the ceiling.

   We have large areas of glazing, so are not kidding ourselves that this place is full enviro-friendly, however am keen to do what we can within our envelope

   Now, there is one section of ceiling that is lower than the rest, and has a lot less insulation potential, and I am keen for opinions:

   From bottom to top it goes something like this:
   140mm joists, yellow tongue directly on joists with colorbond sheet metal gutter directly on the yellow tongue – no sarking, blanket or anything.

   GIven I have 140mm joist space to play with – what is my best option?
   Do i try to from the underside, put some vapor permeable sarking in between each joist to reflect some radiant heat? and with my limited space jam battinsulation up against it?

   Or forget the sarking and go straight bats. I'd be somewhat worried about condensation UNDER the yellow tongue causing it to rot?

   Any ideas welcome.

   Posted Tuesday 20 Jun 2017 @ 12:01:39 am from IP #
2. 

   dave lawrence
   Member

   how wide is this section of ceiling ? and how long ?
   what will the room be used for ?
   what is the proposed ceiling height ?
   is it functioning as a box gutter ?

   Posted Tuesday 20 Jun 2017 @ 10:34:46 pm from IP #
3. 

   jdaley
   Member

   I take it you have heard of the PPPPPP Piss Poor Planning Produces Pathetic Problems, I think this may be your problem.
   What restrictions have you created to produce this problem?

   Posted Wednesday 21 Jun 2017 @ 9:32:46 am from IP #
4. 

   bennygsr
   Member

   8000 l
   900 w
   It is a lowered section above our tv in our living room
   Ceiling height here will be 2400 (rest 3000)
   It is a really wide box gutter above, yes.

   Jdaley -
   I have heard of PPPPPP. And you are right. The restriction is probably having an architect design with a greater emphasiis to aesthetics. But we are also bound by the res code, as we can't have a higher ceiling in this location due building on the boundary.

   No question I wished I'd done more reading here and been more on top of this before the architect and engineers finalised plans, but nonetheless, its a problem I likely can't fix without $$$$ and will prefer to look forward and make the best of a bad situation

   Posted Thursday 22 Jun 2017 @ 11:39:57 pm from IP #
5. 

   bennygsr
   Member

   My plan right now would be:

   Bats, with small amount of air space above them to the yellow tongue.
   Then get a dispensation to lower ceiling height here and put some 50mm insulated plaster board (Kingspan kooltherm). Sure it's expensive, but then I still get some reflective advantages and a little more than just standard plaster.

   Posted Thursday 22 Jun 2017 @ 11:43:47 pm from IP #
6. 

   dave lawrence
   Member

   ask the architect for his/her ideas.. and for clearly annotated details.
   Somebody needs to specify the entire roof section WELL. and then build it as per specs .
   Personally ,I would never contemplate a box gutter unless there were no other options.
   At the very least you need ease access to it ,to enable cleaning it out and checking it regularly . A recipe for disaster if not done perfectly .
   Having said that... It can be done with careful attention to detail. Your first priority is not the insulating properties of this roof .. but keeping it leak proof.

   Posted Friday 23 Jun 2017 @ 5:58:53 am from IP #
7. 

   jdaley
   Member

   Box gutters will always eventually leak, unless they have a steep slope and discharge to the air so there is no build up of anything.
   I understand architects, I am a civil Engineer and they are all away with the pixies.
   The "greater emphasis to aesthetics may make the architect feel good and cause problems for you in the long run.
   Building codes are another matter and that well may be the issue, but if the room is big, why not pull it in from the boundary and get the gutter and the insulation right.
   You may have to stand up to the architect after all you are paying the bills!
   Sometimes a bit of lateral thinking goes a long way, and any building professional who says' no 'from the start is doing themselves and the client a disservice.
   Try a bit of brainstorming with some mates over a beer, you all may be surprised.
   Good luck.

   Posted Friday 23 Jun 2017 @ 7:35:35 am from IP #
8. 

   bennygsr
   Member

   Thanks for the replies.

   The plumber is of the opinion that the design is safe. We have a 900mm (approx) wide and 8m long gutter. It is completely open and resembles a small man made creek so it can't really get blocked up?? It then runs to a trap that has an extra open pipe to drain to the ground. Additionally - it is already built. Both the builder and plumber both say it's perfectly "safe"?

   Given their assurances, I am planning on putting a thick "anticon" style blanket in between these joists - giving me the radiant barrier also. Should I face it toward the yellow tongue (and leave a small 2cm gap) or face the plaster underlying? Will I have a condensation issue here and thus just use a regular batt - but then I lose the radiant barrier here.

   Posted Wednesday 28 Jun 2017 @ 12:28:14 pm from IP #

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