# Forum Home Renovation Roofing  Roof Insulation and Ceiling Joist Spacing

## Gooner

I am about to get some quotes for roof insulation and was in the roof today measuring the distance between the joists. 
I noticed that the joist spacing is quite variable. Anything between 520 and 580mm. Then there is the odd section with 450mm spacing or less. (This is measured between the inner sides of the joists). 
Is this normal/typical? Will this cause problems when getting someone in to install batts?

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## SilentButDeadly

Very typical.  But batts typically come in two to three widths (eg. Bradford is in 430 and 580mm) to cover most options and the batts themselves are very easy to cut with a sharp knife (I use a drop point skinner like this one http://www.everten.com.au/product/de...e-012-6bu.html  
Anyone who says it is a problem is......exaggerating.

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## Gooner

Good to hear. Here's another question... Generally, whats the best type of insulation that comes in batts? Polyester, glass wool, sheeps wool? From what I have read, the general answer seems to be glass wool, with polyester being more expensive. This begs the question of why go polyester if glass wool is a better product and costs less?

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## bugsy

i use garden hedge trimmers.
cuts very nicely without dust etc going everywhere

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## GraemeCook

> I am about to get some quotes for roof insulation and was in the roof today measuring the distance between the joists. 
> I noticed that the joist spacing is quite variable. Anything between 520 and 580mm. Then there is the odd section with 450mm spacing or less. (This is measured between the inner sides of the joists). 
> Is this normal/typical? Will this cause problems when getting someone in to install batts?

  
Totally normal.   If the batts are only a little wider than the gap between the joists then just jamb them in - the tight fit will help the insulation by minimising infiltration.   Its gaps in the insulation that you have to avoid - they're the equivalent of a leaking pipe! 
Cheers 
Graeme

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## SilentButDeadly

> Here's another question... Generally, whats the best type of insulation that comes in batts? Polyester, glass wool, sheeps wool? From what I have read, the general answer seems to be glass wool, with polyester being more expensive. This begs the question of why go polyester if glass wool is a better product and costs less?

  The answer to this question involves cans, worms and marketing. 
Glass fibre is cheapest because 'they' make tonnes of the stuff.   
The alternatives like PET, polyester, wool, newspaper etc. all work in much the same way as glass wool although you could argue that these products are less thermally responsive than the glass fibre (which is technically a better thing).  How significant this technical difference is......is open to question 
The major point of difference is that these products are aesthetically 'nicer'  than glass wool - they are either kinder to the environment in some largely unspecified way, more pleasant to fit or just give the consumer a warm and cuddly feeling.  Because of marketing.....nice costs more. 
How much extra do you want to pay to be 'nice'?   :Blush7:

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## Gooner

> The answer to this question involves cans, worms and marketing.
>  ........ 
> How much extra do you want to pay to be 'nice'?

  Well at the moment I have had a few quotes that range in price by over $1200. 
I have about 150 sqm of roof to insulate with good roof access and no current insulation.  
I have been quoted in excess of $2500 for polyester batts by two different companies. I have had a quote for around the $1600-$1700 mark for glass wool and one just under $1600 for "earthwool" insulation. I do not see why the polyester is so much more expensive. I have not read anything which makes this type of insulation worth over $1000 more. So its probably the standard glasswool type product or the earthwool for now.  
They all seem to do the job and I can't really spot significant pros and cons for either, other than "reduced formaldehyde content" or "absorbs and releases moisture better". They are all pretty much guaranteed for the life of the structure and are all R4 rated..... so whats the difference?

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## Bloss

Fact is there is no difference in what they are used for - insulating! So for the same R-value (in this case R4) then you just want the cheapest batt you can get. Installation in any roof is easy regardless of spacings - as has been said cutting to fit is not problem. Of course if there is more cutting then more time so labor might be up a little, but any quotes you get should be after an inspection (or fixed price - or better still both). 
For most people the batts go in and they never see them again - so just get cheapest R-4 you can find with the best installation deal.

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## Gooner

> For most people the batts go in and they never see them again - so just get cheapest R-4 you can find with the best installation deal.

  Yeah..seems the way to go. I can't understand how people are quoting almost $3000 when others can do it for half the price.

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## SilentButDeadly

One word: rebates 
If the government offers rebates on a product then that immeadiately distorts the asking price.  And there's rebates available for insulation from the Feds.....

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## GraemeCook

> One word: rebates 
> If the government offers rebates on a product then that immeadiately distorts the asking price.  And there's rebates available for insulation from the Feds.....

  
Yep, plus the effects on supply and demand.   With the rebates demand soared to exceed supply and the quick-buck merchants saw the opportunity to raise prices. 
I had never heard of "Earthwool" before so I googled and their website said:  Made with recycled glass bottlesA natural earthy colour 
Seems Earthwool may be yet another brand name for fibre glass wool batts - anyone know anything different? 
Cheers 
Graeme

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## SilentButDeadly

Your description of 'Earthwool' sounds about right to me........but I'll wager they are more exey than the plain old vanilla glass fibre batts.

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## Gooner

They are not more expensive as far as I know. In fact the quote I have obtained for earthwool insulation is the lowest. From what I have read, they are basically glass wool batts with the main difference being the process used to bond the fibers. 
Most insulation guys are telling me it will be a 3-8 week wait due to supply issues. The guys laying down the earthwool say its readily available and can do the job within 1-2 weeks. This is just going off my experience.

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