Wall insulation 100mm cavity Best form

sydthebeat

bauderline wrote: »

syd,

Thanks for that, the wall U values look pretty good. Did you use builddesk for that ?

b.

yes... its a very helpful tool.

ircoha

DLBuild wrote: »

Okay, I'm delighted you guys are addressing some of the concerns and questions I have regarding drylining also.
I'm stuck with a cavity build so I want to gain best results possible in terms of heat retention within the building.
A few points regarding bauderlines methods above which may be obvious to you gusy but not so obvious to me are
4.1 Why the need for battens at point 4. if the insulation is being dabbed to wall couldn't you do without battens altogether.
5.1 Is this foil backed insulation at point 5 between the battens or the non foil backed stuff.
Also, and vitally, how do you work with openings? i.e. would you do the same detail at window openings i.e. top, bottom, left and right and reduce your window size?
Many thanks.

IMO the battens are to fix the second layer of insulation and the plasterboard to as u cant dab again.

re the opes this has been kicked around a bit as well, if u thought sorting out the wall was tough, it was a walk in the park compared to agreeing cold bridging details:).

look at http://www.planningportal.gov.uk/england/professionals/en/1115314255826.html

Also search the C+P forum for cold bridging, thermal bridging etc, I have started a few posts on the topic and have benefited from the expertise of others here.

Finally browse some of the product sites such as rockwool.co.uk for sketchs of details: I am not advocating rockwool as a product but their sketches show the principles very well which apply regardless of insulation product.

One suggestion is that u make the frames wider than normal so as when u wrap the inner reveal with 25mm PU or similiar u still have some frame visible, this requires an extra layer of plaster outside on the reveal.

sinnerboy

bauderline wrote: »

Okay....

I am not giving up yet....

I know that cavity wall construction severely displeases some you and I understand the issues with it, however lets work on the basis that I can ensure that the insulation is installed to a high standard and meticulous attention is given to detail.

good luck with that ......:rolleyes: I have seen this achieved once since 1982

[/QUOTE=bauderline;55194907]

I have 310mm width of wall to play with so ....

1. 100mm block outer leaf.
2. 110mm cavity which contains 70mm insulation and a 40mm cavity.
3. 100mm block inner leaf.
4. Install battens on inner leaf. (50x25)
5. Install 50mm of PU between each batten using dot dab method.

[/QUOTE]

no- run over and screw fix to battens . foil tape joints

bauderline wrote: »

6. Install another 50mm of PU over existing 50mm insulation and battens. Should be foil faced on both sides. Using long fixings.
7. Foil tape all joints in an effort to prevent air leakage.
8. Cover with 12.5mm foilbacked plasterboard and skim.

This will give me 170mm of insulation and should minimise condensations issues should it not ?

And now to ask the questions...

1. Considering I am hell bent on cavity wall construction is this the way to do it ? If not WHAT specifically have I got wrong.

do what you want to do - I can't reapeat myself endlessly

[/QUOTE=bauderline;55194907]


2. Do I really need a layer of polythene in there ? If so where EXACTLY should it go.

[/QUOTE]

on the warm side of the innermost insulation layer . OR use foil backed plasterboard

[/QUOTE=bauderline;5519490

Thanks for your time !

Best regards, Baud.[/QUOTE]

Sorry , I have not mastered the multi qoute bit yet .....

DLBuild

Argggggh.
Just when I thought I was getting somewhere my mind asks another million questions re drylining.
Mainly now i'm thinking, 100mm of drylining as proposed here would mean it would be really difficult if not impossible to hang curtain rails etc. Are there ways and means around this?
Also, in the detail provided above, is the layer of insulation next to the inner leaf block foil backed or not?
I spoke to a guy from Kingspan last week. He mentioned they have drylining boards, one without foil for sticking to wall with dabs and one foil backed for battening. Any thoughts?
I've got a feeling this is going to lead to more questions. I appreciate everyones patience.

sinnerboy

DLBuild wrote: »

Argggggh.
Just when I thought I was getting somewhere my mind asks another million questions re drylining.
Mainly now i'm thinking, 100mm of drylining as proposed here would mean it would be really difficult if not impossible to hang curtain rails etc. Are there ways and means around this?

hardwood grounds . keep as small as possible . use to hang rads too

DLBuild wrote: »

Also, in the detail provided above, is the layer of insulation next to the inner leaf block foil backed or not?

yes

B&T

Hi All,
Sorry for butting in but regarding condenstaion I had one question on work I have done on my own self build and may have to redo!
In the opes for windows etc I have put in 1 " thick by 6 inch wide double foil kingspan strips into the remaining opening between L block and outer leaf. the Damp proof is only 4" wide though. I then sealed (& to hold in place) the insulation to blockwork using expanding foam.
This to me looks like a great job and looks like it will really seal from draughts in the cavity.
Question is though Is there a risk that the 6" overlap on the 4" DPC will be an oppurtunity for damp to come towards the reveals.
The reason I used the 6" strips is to overlap properly internal cavity insulation already in place.
Should I undo this work is the the risk of moisture ingress low

Thanks B&T

sinnerboy

I would think the risk is low . do a hose test to ease your mind .

B&T

Thanks Sinnerboy.
I might try that hose test and see what I get. I since chatted to the engineer to ask advice. He seemed to think it should be fine!

B&T

sydthebeat

neilsbreak wrote: »

SNIP

Its very dangerous for Kingspan to be putting out info like that...... it seems to purport that insulation levels is the be all and end all of the BER procedure... which it isnt.

At an A2 level, boiler efficiency + heating controls, ventilation specification, and design for solar gains are possibly even more important....




Edit by muffler: Sorry Syd, had to get rid of a muppet's work

Rigney

Hi Just my 5 cent worth...

If you have 310mm width of wall to play with try:

1. 100mm block outer leaf.
2. 110mm cavity which contains 110mm insulation
3. 100mm block inner leaf.

<SNIP>
he construction of walls with cavities in excess of 110mm wide would require adjustments to lintels, wall ties, cavity barriers, etc. It is therefore necessary that cavity walls are adequately designed in respect of structural stability.[/LEFT]

You can then driline to achieve even better U-value!:D

sydthebeat

according to the table supplied 'certainfil' grey bead in 110mm cavity with 1700kg/m3 block only gives a u value of 0.26....... thats not a good result considering.....

.....that to increase the partial fill from 60mm to 70mm would probably result in a similar u value (on paper)

muffler

Very poor spammed advice given syd. - Sorry not by you but by Rigney who has now gone on holidays