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

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

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.

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"?

"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

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"?