[Strawbale] Foams

[Andrew Webb]

Hi Doug,

Your points are valid and you are right that reflectivity is important 
in this climate.  That is another potential problem with sandwich panels 
because there is no air space in the system to have a reflective layer.  
However, the roofing itself can help a bit if kept white or 'natural' 
zinc (which does dull over time).  I haven't done any thermal modelling 
of these sandwich panels vs a composite system with reflective foil, but 
will soon.  I suspect that an R4.8 sandwich panel will outperform a 
composite system with R3.5 reflective batts (+ minor contributions of 
other layers).  I also suspect the sandwich panel will cope as well or 
better with humidity than a composite system.  Delamination of the 
sandwich panel is a potential downfall. 

As H.W. said, longevity is an important goal but, as I said a few weeks 
ago, it is not necessarily something you can guarantee despite your best 
efforts.  Therefore I aim to minimise energy use, greenhouse emissions, 
unfair trading, dangerous manufacturing practices and environmental 
degradation with every decision; while working within a conventional 
building industry and housing market.  So, I keep questioning.

-AW



Leanne Rellstab wrote:
> ....
> Don't forget to match the product's resistance to humidity over the 
> long term because sub tropical means more humidity.
>
> Doug