Insulation - partial/full fill
Discussion
Can someone clear up some points for me i nrelation to insulation that goes into the cavity of (newly) built walls for houses.
I understand that the insulation boards that you can buy are partial fill - so you need to leave an airgap - does anyone know what happens if you don't leave a space? Damp? What if the wall is sheltered - i.e there is no chance of it getting wet from rain.
I understand the mineral roll type stuff is full fill. A buidler I was talking to says you need to leave SOME gaps because the way he does it is build a few course of block/brick and then put the insulation in - and you need soem leeway to actually squeeze it in. So my query is ocne it is in, if it is not crammed in touching block and brick on either side does it matter too much?
I woudl have thought a smarter way to have done it owuld be to build the block, then put the insulation in and then build the brick - that remvoes the issue of trying to put something between the gap and the ties being in the way.
I have been gettign conflciting advice from builders hence my queries.
I understand that the insulation boards that you can buy are partial fill - so you need to leave an airgap - does anyone know what happens if you don't leave a space? Damp? What if the wall is sheltered - i.e there is no chance of it getting wet from rain.
I understand the mineral roll type stuff is full fill. A buidler I was talking to says you need to leave SOME gaps because the way he does it is build a few course of block/brick and then put the insulation in - and you need soem leeway to actually squeeze it in. So my query is ocne it is in, if it is not crammed in touching block and brick on either side does it matter too much?
I woudl have thought a smarter way to have done it owuld be to build the block, then put the insulation in and then build the brick - that remvoes the issue of trying to put something between the gap and the ties being in the way.
I have been gettign conflciting advice from builders hence my queries.
Partial fill - the rigid boards lined with foil such as Kingspan, Celotex, Extratherm etc come in 1200x450 sheets and should be fitted to the inner leaf blockwork with a 50mm clear cavity. It should not be used as full fill.
Full fill, flexible fibreglass or mineral wool 'cavity batts' made by companies like Knauf or Rockwool. Comes in sheets of 1200x450mm and doesn't need a clear cavity, infact because they are flexible they should ideally be installed as full fill to hold them in place. Normally attached to the brickwork as it has been built with the blockwork built afterwards.
As a general rule to achieve the same U value you need twice as much full fill as you do partial fill - to achieve current Building Regs wall U value of 0.28 you will need 50/60mm partial fill and 100mm ish full fill.
If your project needs Regs, make sure you clear you proposals with the BCO. If your builder wants to do it differently, be wary.
Full fill, flexible fibreglass or mineral wool 'cavity batts' made by companies like Knauf or Rockwool. Comes in sheets of 1200x450mm and doesn't need a clear cavity, infact because they are flexible they should ideally be installed as full fill to hold them in place. Normally attached to the brickwork as it has been built with the blockwork built afterwards.
As a general rule to achieve the same U value you need twice as much full fill as you do partial fill - to achieve current Building Regs wall U value of 0.28 you will need 50/60mm partial fill and 100mm ish full fill.
If your project needs Regs, make sure you clear you proposals with the BCO. If your builder wants to do it differently, be wary.
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