300mm loft insulation?
 

Is there any reason not to use 300mm of loft insulation rather than the
270mm specified?

It actually would be cheaper to use 3x100mm layers than the normal 100mm
layer with a 170mm layer on top as there would be no waste left over.

Adam

300mm loft insulation?
 

ARWadsworth wrote:
Is there any reason not to use 300mm of loft insulation rather than
the 270mm specified?

It actually would be cheaper to use 3x100mm layers than the normal
100mm layer with a 170mm layer on top as there would be no waste left
over.

Adam

Adam

None whatsoever - the specifications for the thickness of loft insulation
changes according to the thinking of the day, and when my house was built in
the '70's, the loft was covered with a layer 1/2" thick - it's now 300mm.

NB: Just try and keep cables that supply any electric shower above the
insulation - or if that is not possible, leave it free in a 'valley' in the
insulation.

Cash

300mm loft insulation?
 

On Dec 21, 5:45*am, "ARWadsworth"
wrote:
Is there any reason not to use 300mm of loft insulation rather than the
270mm specified?

It actually would be cheaper to use 3x100mm layers than the normal 100mm
layer with a 170mm layer on top as there would be no waste left over.

Adam

Dont you rate it by R value, so what are you buying? In the US we do.
Different types of insulation have different values and it goes from R
3" to R 7.2" fpr polyisocyanurate foam. Many types settle up to 20%,
Code for me is minimum R 35 attic and I have R 100. Did you know
Fiberglass looses about 20% of it R value at 10f? Codes are minimums
depending on type and how cold your area is, and figure in settling
maybe 450mm is correct for you. 300mm is about 12" or R 45 which is ok
if it doesnt settle or get real cold where fiberglass looses R value.

300mm loft insulation?
 

ransley wrote:

Dont you rate it by R value, so what are you buying? In the US we do.
Different types of insulation have different values and it goes from R
3" to R 7.2" fpr polyisocyanurate foam. Many types settle up to 20%,
Code for me is minimum R 35 attic and I have R 100. Did you know
Fiberglass looses about 20% of it R value at 10f? Codes are minimums
depending on type and how cold your area is, and figure in settling
maybe 450mm is correct for you. 300mm is about 12" or R 45 which is ok
if it doesnt settle or get real cold where fiberglass looses R value.

On this side of the pond we use U-values, which are the reciprocal of
the sum of the R-values. That way we can trade-off heat losses, and take
account of thermal bridging. We use metric units, rather than imperial,
so resistance is measured as metres^2.degrees Kelvin/Watts. The maximum
U-value for roofs is 0.16W/m^2K (or less depending on the overall carbon
emissions), which is a R-value of 6.25m^2K/W, of which the insulation
(plus ceiling joists) would need to be about 5.86m^2K/W. How that
relates to your imperial units, I'm not sure.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed"?

300mm loft insulation?
 

"Huge" wrote in message
...
On 2008-12-21, Hugo Nebula abuse@localhost wrote:

How that
relates to your imperial units, I'm not sure.

http://en.wikipedia.org/wiki/U-value#Units

Wonder what happens if I paste the conversion equation? Here we go ...

1 ft²·°F·h/Btu ? 0.1761 K·m²/W, or 1 K·m²/W ? 5.67446 ft²·°F·h/Btu.

--

I put 3 layers of 100mm down. Just 50% extra work. But no waste.

Adam

300mm loft insulation?
 

Huge wrote:
On 2008-12-21, Hugo Nebula abuse@localhost wrote:

How that
relates to your imperial units, I'm not sure.

http://en.wikipedia.org/wiki/U-value#Units

Wonder what happens if I paste the conversion equation? Here we go ...

1 ft²·°F·h/Btu ? 0.1761 K·m²/W, or 1 K·m²/W ? 5.67446 ft²·°F·h/Btu.

Thank you for allowing me to make the correction. After, "How that
relates to your imperial units", replace text with, "I can't be arsed to
look up".
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed"?