# Forum Home Renovation Flooring  sarking - shiny side facing ground or blue side?

## hitsam

Hi. 
Just joined... great place you got here  :2thumbsup:  
I'm looking to insulate under my house, timber floor on stumps. 
I've decided to use sarking but I'm confused about which way to attach it. 
Should I have the shiny side facing the ground or the blue side facing the ground? 
Thanks.

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## autogenous

If shiny side up gets covered in dust will it still reflect temperature? 
It sounds like, if you scream in a forrest with no one there will any one hear you  :Biggrin:

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## nww1969

> If shiny side up gets covered in dust will it still reflect temperature? 
> It sounds like, if you scream in a forrest with no one there will any one hear you

  Yeah I can see where your going with that one. 
But my understanding is the only reason they paint one side blue is to try
and stop the glare for the builders,.
can you imagine a nice sunny day and a roofer trying to do his job roofing
looking at the silver reflection, blue cuts the reflection down.

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## hitsam

> If shiny side up gets covered in dust will it still reflect temperature?

  Ok fair point, leaning towards blue side down, anyone else?   

> It sounds like, if you scream in a forrest with no one there will any one hear you

  
Or perhaps... 
If a man speaks in a forest and there is no woman around to hear him,
is he still wrong?  :Cool:

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## Bedford

Hi Hitsam, whenever we've done this we put the reflective (silver) side down as instructed by building inspectors. 
. You may also need to put bats in between the joists to increase the affectivness.

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## Bloss

This handbook is useful to show how things go together for insulation.  http://www.icanz.org.au/pdf/17132_ICANZ_HANDBOOK.pdf 
For example for a timber floor there is 19mm of timber and you can have regular sarking foil attached to the bottom of the joists. 
If you want to have batts too you use breathable foil such as is used in wall wrapping (but not as roof sarking). 
Depends which direction you are trying to have the biggest effect - heat flowing down (from inside the building in winter) or heat flowing up into the house in summer. Most effective is winter use and for that the shiny side should face up in a retrofit (glare is not an issue) - difference is not huge though - and you can get shiny both sides too! Worth paying for the better quality foils too - more substantial harder to damage etc. 
See here - biggish file though (1.2MB)   http://www.timber.org.au/resources/I...%20Systems.pdf 
See sheet 2 on page 30. Note that the effectiveness is quite different with an open or enclosed sub floor.

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## Bloss

> Hi Hitsam, whenever we've done this we put the reflective (silver) side down as instructed by building inspectors. 
> . You may also need to put bats in between the joists to increase the affectivness.

  Shows you how much that inspector knew . . .  :Rolleyes:   :Smilie:  
As mentioned if you are using batts then use the breathable foil (and if in humid areas that applies to deal with condensation). If you seal the airspace with foil and tape etc with good overlaps you get an R-value of around 1.8 to 2.5 - plenty enough for floors in most areas. 
Note a big improvement from sealing the gaps at the base of the wall cavity (while ensuring there is sufficient underfloor cross ventilation) gives big improvements all year round. BCA slow to catch up, but building practice elsewhere in the world has acknowledged this for 20 years or more!  :Frown:

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## Bedford

> Depends which direction you are trying to have the biggest effect - heat flowing down (from inside the building in winter) or heat flowing up into the house in summer.

   

> Shows you how much that inspector knew .

  This was in a very hot climate and predominatly for cooling, I should have mentioned that ...sorry.

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## jatt

Picked up some concerina foil for the subfloor I'm soon to be insulating.  Reasoning is that I have ifferent spacings between bearers across span of floor.  Packaging says rating of 1.9 .  Holes at intervals for condensation to drip out. 
Obviously one needs to attend to  sealing the air space. 
5 star mob is happy with choice 
Another option I was presented with is Silverfloor.  Basically a 500 mm wide roll thats stapled between joists spaced at 450 mm.  Most of my spacings are wider than that, so of couse this is not a good option for me.

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