How much insulation goes into new loft extensions or new builds

[Mr_T25]

I'm curious to know how much insulation goes in the loft of new builds or even loft extensions. Forget about what u values you want to achieve, just want to know what is the norm these days.

 

[roboughton]

Well on a new build its what is specified in the build drawings and the same goes for extensions. If its not under building control then most probably anything between nothing a 300mm depending what you are doing or who is doing it.

 

[ey143]

Wow - so I thought 100mm was good (board type). Is even 150mm considered below average?

 

[GeoffJ]

Hi

This web site says http://www.thinkinsulation.co.uk/up.../how-much-insulation-do-i-need/#axzz43k4j0PHN

Says "Current building regulations recommend a minimum depth of 270mm"

Geoff

 

[Mr_T25]

Ok and I agree with mineral wool type yes, we will have 270mm in the flat section. I meant the sloping section of the roof using board insulation.

 

[roboughton]

Ok and I agree with mineral wool type yes, we will have 270mm in the flat section. I meant the sloping section of the roof using board insulation.

Most probably 120-130mm of The roofing type of board (there are different spec of boards) then to meet regs for U value, of if no U value then what ever you can get to fit that allows ventilation still

 

[Mr_T25]

So 150mm kingspan in the rafters should be super insulated then?

 

[tony1851]

Yes, but would there be space for ventilation?

 

[Mr_T25]

using breathable membrane and 25mm air gap in the rafter.

 

[^woody^]

It depends on the insulation type, the average u values of the rest of the build and the elimination of thermal bridges.

So "how much insulation" is unanswerable.

 

[chappers]

for a conversion 90mm between with 50mm below the rafters would be about right for a pitched roof or as suggested about 150mm between.
more for a new build as the u-value requirement is higher.
Reesey 70mm between with tri-iso 10 would probably leave you a bit short, but you would have to speak with BC, they may let you away with that.
BC where I am require 90mm between and tri-iso under the rafters, but the height saving is zero. tri-iso 10 is 30mm thick so by the time you have battened over it, you may have used 12.5mm bonded to 50mm rigid insulation

 

[^woody^]

Not forgetting that Tri-iso might not actually work.

 

[jeds]

Forget multi foils. To be anywhere near effective (if that's even possible?) they need to be suspended in clear air gaps both sides. That's difficult to achieve in practice and in fact is rarely achieved meaning most multi foil insulation is just expensive bubble wrap. A 50-60mm layer of pir foam is far better, easier to fix, cheaper and will take less space.

 

[mointainwalker]

[QUOTE=". And the 2 layer will provide me with the 0.18 required and a lot quicker to install.[/QUOTE]

So just how are you going to create the clear, sealed air-spaces either side of the multi-foil and do this
[QUOTE=" a lot quicker .[/QUOTE] ?

 

[^woody^]

Has superquilt got BBA certification now, and do all building control depts now accept it?

I suspect that there are reasons why a manufacturer would make a convincing video, and say that it meets all regulations.