Fullfill insulation in a 75mm cavity to reach 0.28?

[cox377]

Hello guys,

Does anyone know of a full fill insulation that would hit 0.28 in a 75mm cavity?

This is working out my options before building control tell me to rip out the celotex thats already in there which I'm sure will be the out come next week.

Thanks in advance

J

 

[theoldun]

Coxswain

There is no full fill cavity insulation on its own for 75mm cavity to achieve 0.28W/m2K

Tell us why you think that you have to pull 40mm celotex partial fill insulation out, and we in all probability will tell you why you do not have to.

Do you know the block lambda value (resistance value) of the block that you used or the name of the block manufacturer and the block name.
Regards oldun.

 

[^woody^]

It will depend on what is being used for the cavity wall, as to what insulation is required in the cavity

 

[theoldun]

If all these mortar snots are pushing the insulation forward, then you will never get it back tight against the blockwork without demolishing one of the skins

Board insulation is bad enough to use for pro work, let alone DIY

Your options do seem to be limited

Taking down the blockwork may be easiest, and with care you can reuse the board rather than change to quilt

Hows that for a clue.
Regards oldun

 

[^woody^]

Oh. Why do people post lots of threads on the same subject.

How is a poor overworked soul supposed to keep up?

Anyway, that still don't say what the blocks are which would help in working out what the cavity insulation needs to be. Or is that in the other thread somewhere?

 

[cox377]

Hello guys,

Cavity wall - 100mm block/ 40 celotex/ 25 air gap / 110 reclaimed bricks

I've got three walls on an extension I'm building. You may remember three weeks ago my post about building control seeing cement between the foil and the outside skin.

A day later my car engine blew up and that set me back. Cut a long story short I used a piece of flat bar to knock a lot of the cement below the DPC line.

The end wall with the windows in, cleared out easily with little ripping of foil. Attached a piece of conduit to a hoover and sucked a lot of it out.

One of the gable walls seems okay. Not much pug was down their but the board itself is not as flush as one would like due to building the brick then the block due to a neighbours shed.

The last wall, insulation was laid flush etc but the foil got torn and so touched the outside wall. I used a large paint brush on the end of a bar to glue the flaps back down. It's not perfect so will need more work. The gaffa tape I got from wickes as I forgot to order has started peiling off so I've bought some double strength water proof stuff to try and rectify.

The BCO talked about using mirrors to confirm the cavities were good as previously discussed. He said I could pull the inner skin down use full fill then king span on the inside to get the u value required. Best 75mm fullfill I've found was rockwall eco which is 0.32.

The celcons used were standards and are 0.15's but I'm guessing they couldnt all be reused once pulled down.

Thank you in advance guys and I appologise that this is getting old.

J

 

[cox377]

Guess we'll wait and see what he says

 

[cox377]

Building control called for tomorrow afternoon. Wish me luck guys.

 

[tony1851]

If your wall U-value doesn't quite come up to 0.28, you can go down the so-called 'area-weighted' route, where you can put more insulation elsewhere in the extension to compensate (eg in the roof).
Whatever you do, don't start pulling walls down just on the inspector's say-so; - there are easier ways to achieve compliance with Part L.

 

[cox377]

hello tony,

Thanks for your response, I was hoping to go down the route to put more in the loft to compensate.

Looking at the Part L doc

http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADL1A_2010.pdf

It states that the highest U value for walls when using area weighted is .30. With Solar blocks and eco rockwall I could hit 0.31

The fullfill was only if he isn't happy with what I've done and requests I pull it down, take king span out and rebuild with fullfill.

It's not the fact that it's not currently up to spec, it's the fact there was cement between insulation and outter skin. I knocked it down to the bottom below the DPC line and some came out through wholes I made in the wall.

Spoke to him this morning, he said to me how can he see the air space is clear down the bottom because it's tight, 25mm.

In regards to other ways to meet part L, are you refering to it being full fill currently?

Thanks in advance

James

 

[tony1851]

It states that the highest U value for walls when using area weighted is .30.



J

I might be missing something but precisely where in L1B does it state this?

In the previous (2006) edition of L1B, there was a stipulation that the area-weighted U-value for a wall should be no worse than 0.35, when using the area-weighted method. That has been omitted from the (latest) 2009 edition, so I would guess that if your existing wall gives no worse than, say, 035 you should be OK and only need to make up for this elsewhere - probably best in the roof.

(Assume your area of glazing is not excessive?)

 

[cox377]

Page 15, think I'm looking at the right thing.

Edit - That was the new dwelling document.

Thanks

James

 

[tony1851]

James, just noticed your latest post which came up as I was editing mine. Yes, you were looking at L1A, which is not for existing dwellings - its L1B you want which covers extensions to existing dwellings
With the insulation you described, I think you will be OK to use the area-weighted method, and just compensate elsewhere.

 

[cox377]

Is there a limit to the u value of walls when using area weighted?

Regarding pulling the walls down, we'll see what he says tomorrow

 

[tony1851]

Is there a limit to the u value of walls when using area weighted?

I don't think one is quoted in L1B in relation to the area-weighted method, but Approved Document C (page thirty eight) advises a minimum of 0.7. Your wall should be well above this.