insulation

[dapperman]

Hi,

I have a brick cavity wall, the cavity is 55mm and was wondering what type of insulation I can use that won’t bridge the cavity and cause problems later on.

To my understanding celotex brand insulation shouldn’t touch both leaves of wall. I have seen wool insulation being used, that fill the cavity up fully but doesn’t this bridge the cavity and won’t this cause the cavity to not function properly?

Thanks

 

[Notch7]

Existing wall?

there are various cavity batts including rockwall and glass fibre that are suitable for new walls - and can be full fill.

there are some rigid insulation products that can be full fill.

all of these are 450mm high to suit wall tie spacing.

but none can be retrofitted

 

[dapperman]

Existing wall?

there are various cavity batts including rockwall and glass fibre that are suitable for new walls - and can be full fill.

there are some rigid insulation products that can be full fill.

all of these are 450mm high to suit wall tie spacing.

but none can be retrofitted

Sorry I mean building one, are you saying i can put rock wool batts inside my walls without bridging the cavity and causing damp?

 

[^woody^]

Cavity batt insulation is designed to fill the cavity with no damp problems. It just requires care with the placement and when building the leafs.

Rigid board requires much more care, and higher damp risk in narrow cavities.

55mm cavity won't meet current regulations

 

[noseall]

55mm cavity won't meet current regulations

And in about one month's time, 100mm cavities will be old news. 150mm cavities here we come.

 

[dapperman]

Cavity batt insulation is designed to fill the cavity with no damp problems. It just requires care with the placement and when building the leafs.

Rigid board requires much more care, and higher damp risk in narrow cavities.

55mm cavity won't meet current regulations

i thought 50mm cavities were the nominal size for a cavity and is allowed, doesn’t it say in nhbc?

 

[^woody^]

i thought 50mm cavities were the nominal size for a cavity and is allowed, doesn’t it say in nhbc?

 

[dapperman]

View attachment 269473

 

[dapperman]

View attachment 269473

Ok ok. Cavity wall with block on the outside and inside. Wall is being rendered on the outside. Now the main concern here is cold bridging right? When warm air hits cold and condensates and causes damp. What cavity would you recommend and what insulation? I’m guessing you have to have insulation in the cavity?

 

[^woody^]

I'm not sure you understand the concept!

Cold bridging is not the term you would use to describe the scenario you mention. Neither is condensation an issue either in this situation.

The requirement is for a wall to achieve a minimum thermal standard, and the wall does not need to be a cavity wall, nor does insulation need to be in a cavity.

With a cavity wall, the qualities of the block matter, so you could reduce the cavity size by using better blocks either side of it, or dry lining the inner face.

A typical make-up is plasterboard on dabs, 110mm standard AAC blocks internal (or 100mm high performance), 100mm full fill Cavity Batt and your choice of external blocks.
Or a solid wall and 80mm internal or external PIR (foil-faced) insulation board

 

[dapperman]

I'm not sure you understand the concept!

Cold bridging is not the term you would use to describe the scenario you mention. Neither is condensation an issue either in this situation.

The requirement is for a wall to achieve a minimum thermal standard, and the wall does not need to be a cavity wall, nor does insulation need to be in a cavity.

With a cavity wall, the qualities of the block matter, so you could reduce the cavity size by using better blocks either side of it, or dry lining the inner face.

A typical make-up is plasterboard on dabs, 110mm standard AAC blocks internal (or 100mm high performance), 100mm full fill Cavity Batt and your choice of external blocks.
Or a solid wall and 80mm internal or external PIR (foil-faced) insulation board

If i need to do a 100mm cavity i will it’s the right way to do things, what I do not want however is damp from bridging the cavity, so i need to know if the full fill will cause damp?

Also say I didn’t put insulation in the wall and left it at a 50mm cavity, what would happen other than heat loss and a cold wall?

Cheers

 

[tony1851]

The cavity batts have a coating on the side which repels water, and they are easier to fix than rigid boards.

As Nose says, things are-a-changin' from mid June. You can either have 150 cavities with 2 layers of 75mm batts; or a 125 cavity with 75mm PIR board fixed to the inner skin. (Both methods requiring aac block internally).

 

[dapperman]

The cavity batts have a coating on the side which repels water, and they are easier to fix than rigid boards.

As Nose says, things are-a-changin' from mid June. You can either have 150 cavities with 2 layers of 75mm batts; or a 125 cavity with 75mm PIR board fixed to the inner skin. (Both methods requiring aac block internally).

Also say I didn’t put insulation in the wall and left it at a 50mm cavity, what would happen other than heat loss and a cold wall?


Read more: https://www.diynot.com/diy/threads/insulation.591488/#ixzz7T122cbAT

 

[tony1851]

Also say I didn’t put insulation in the wall and left it at a 50mm cavity, what would happen other than heat loss and a cold wall?

As well as a cold wall, presumably you would also have the Building Inspector on your back for not complying with Part L of the regs?

 

[dapperman]

As well as a cold wall, presumably you would also have the Building Inspector on your back for not complying with Part L of the regs?

This is what I will do. 100mm cavity with 100mm or 50mm rock wool batts. Which would you recommend?