Alternative Technology Assn Forums

1. 

   kd
   Member

   Hi,

   I'm just finalising the design for a steel framed/colorbond clad house (pale colours!) in the Illawarra (just a shade cooler than coastal Sydney), and I"m wondering what people's thoughts are about what R value the ceiling and floor insulation should be. I see that the VIC government legislates for R 1.3 for walls and R 2.2 for the ceiling. Our kit home fabricator has specified R 1.5 for walls and 3.3 for the ceiling, which seem to be inline with the VIC sustainable energy authority for coastal areas.

   The house faces north and is designed to pick up the majority of its winter heating needs through solar gain, and we're dealing with providing internal thermal mass to achieve that.

   We're frost-free here, and only really have a handful of days where temperatures exceed 30ºC. "Cold" here means when it gets to minimum temperatures of 8-10 degrees or so (4 is possible but rare at maybe 1-2 days per year).

   Any thoughts on what wall and ceiling insulation would be optimum for our situation. At what R value would I just be throwing my money away do you think?

   Posted Saturday 26 May 2012 @ 11:18:26 am from IP #
2. 

   dymonite69
   Member

   The answer is partly related to your comfort levels - at what temperature you would consider turning on the heating or cooling. If you can bear living in a tent, then technically you need no insulation! Although the incremental returns lessen with additional insulation, over the course of the life of the house even with R 6 batts you would pay of the savings in additional heating or cooling in less than 10 years and possibly faster if you often use artificial conditioning.

   Posted Saturday 26 May 2012 @ 3:13:15 pm from IP #
3. 

   dave lawrence
   Member

   a combination of factors will determine the answer.
   for example : if your glazing is inappropriate (too much facing west etc ) then the insulation will have to work that much harder to achieve less. in other words the insulation is but one piece of the puzzle

   Posted Saturday 26 May 2012 @ 8:52:15 pm from IP #
4. 

   kd
   Member

   Well our goal is to have a house that needs no artificial cooling other than ceiling fans, and limited heating (one wood burner to be used lightly - design somewhat undecided at the moment). There is no west facing glazing and very limited east facing glazing. Eaves on the north facing windows (to about 15% of floor area of the north facing rooms), and reasonable levels of thermal mass in the lower floor (it's a one-and-two storey house due to being built on a north facing hillside). I think we're going to have laminated low emissivity glass rather than double glazing.

   Posted Saturday 26 May 2012 @ 10:53:36 pm from IP #
5. 

   dave lawrence
   Member

   sounds good .
   insulate to high levels and ensure installed as per manufacturers specs .

   Posted Saturday 26 May 2012 @ 11:13:05 pm from IP #
6. 

   ghostgum
   Member

   What sort of insulation are you using?
   Given that it is a steel frame, are you being careful to provide a thermal break between the steel frame and the outside cladding? For example, a layer of EPS or PIR board betwen the roof sheets and the steel frame? The same would be desirable on the walls.

   Posted Monday 28 May 2012 @ 1:14:09 am from IP #

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