Adventures in Wall Insulation

Decided on Sunday (9th) that since the house was open, some of the sarking (internal wall lining) was off and it would remain that way for a week I should make a quick and dirty attempt at insulating the exterior walls.

This intent was driven by memories of how cold these villas can get in winter (I flatted in one for a time while I was at University), how cold the winters get in Taranaki and the realisation that our time in California has removed any tolerence we may have had for the NZ cold.

And insulation happens to be the cheapest and most effective way of making a building heat efficient (about 24% of Heat loss is through walls)- we're gonna mass insulate the ceilings and floors also once the building work is completed.

Being that we weren't taking off all the sarking (interior house lining - basically 25mm thick planks) and the house should have a year or so to stand and dry in its new orientation it wasnt possible to insulate with fiberglass wool (called Pink Batts here), instead should use something that wouldnt hold moisture.

Building standard insulation for walls in this area is R1.8
(R value is a measure of how well something doesnt conduct heat.
R1 is about the conductance of an inch(25mm) of wood,
the same thickness of fiberglass batts is about R3,
styrofoam about R5).
Theres at least 50mm of wood in the walls (weatherboard outer and inner sarking - they made the walls thick in the old days) with a gap between and the interior is going to be gib (sheetrock) lined so any little bit extra should be fine.

I figured if I could get something with an R factor of above 1.0 I'd be doing OK.

I thought closed cell foam would be a good material (R2ish or more in 20mm), failing that styrofoam sheets both of which I thought I could bend enough to get down the sarking gap without breaking it. Fortunately these old villas dont usually have dwangs or noggins between the studs, the boxing of the outer weatherboard and inner sarking evidently provided enough rigidity.

Theres at least a 50mm gap, probably more like 75-100mm. I figured 25-40 mm of material should provide some insulation and be flexible enough to be forced in.

What would be ideal is foil lined bubble wrap but I couldnt find any suppliers of it in NZ - not as a building/insulation supply anyway (plenty in the States according to google).

OK so what about building foil and just bubble wrap?
Hmm whats the R value of bubble wrap?
Back to the web:
While looking for something or someone who'd been perverse enough to actually formally test bubble wrap for its insulating possibilities I came across a very interesting article about using discarded plastic bottles as insulation in Nepal.

PLASTIC WASTE INSULATION FOR HIGH ALTITUDE AREAS

Well that works for me too, We dont get anywhere near as cold as Nepal - Its all just ways of making air sit still. I'll ask my relatives to collect all their plastic bottles for a week or so and if thats not enough I'll go to the transfer station and get some more.

Right back to bubble wrap - where do I get that from ?
packaging places, fire up google again.
Well look at that; as well as bubble wrap some of them have a foil lined bubble
wrap product as well (its a product called air-cell and its australian).

Right I'm set
closed cell foam, styrofoam, foil bubble wrap, bubble wrap and plastic bottles
I'll get costings and maybe try some of each and see if theres any noticeable
difference.

Spent some of Sunday night Oct 9th and all of Monday Oct 10th googling for building suppliers, looking at web sites and ringing around New Plymouth. In the process I discovered that while most of the large NZ building supplies suppliers have websites, none of them have any clue about what to use it for.

I got extremely frustrated with one in particular after being subjected to a barrage of corporate bumf and unbelievable excuses of why they couldnt post their product line online and (when I managed to find their feedback page) sent a nasty little missive aboout what they should be doing with 4 or 5 immediate points they should correct.
To their credit I got a nice reply from some marketing person thanking me for the feedback, apologising for my negative experience and saying they were going to review their web site soon. She also offered to take a list of the materials I was looking for and get some quotes for them directly ... Too late - by then I'd already chosen suppliers and made the orders and it wasnt from them.
Still bless their corporate little dinosaur hearts, they can roar and crash around and all the while the proto-mammals are eating their eggs.

So Monday, ascertain stock levels and pricing and make orders....
At the end of the day:

• Closed cell foam - unbelievably expensive, forget it
  
• Styrofoam - cheap but some suppliers not have in stock, some doubt as to if it would be flexible enough. Decide its too much hassle to transport as we have:
  
• Foil wrap: Found a good cheap supply 100m x1.2 m rolls for about $400 ($4/m), unrated as to R value but believed 'comparable' to similar products.
  
• air-cell expensivish ($10/m) and its in smaller rolls so I'll just use a bit of it.
  
• Bubble wrap - cheap I'll get a 60m roll just for laughs.
  
• Screw the building foil,
  
• The transfer station will sell me a trailer of bagged plastic bottles for $50
  

All sorted, will get the wall insulation for about $500.
Batts would have cost about twice that.
Pick the stuff up on Thursday. With any luck start installing it Friday.