external wall insulation / cavity

[CharlotteJ]

Hi, we are converting a concrete block building that was originally built around 2007. It has 7n concrete blocks (100mm thick) external walls apart from gable ends and the long rear wall which are all 7n concrete blocks on the flat side (215mm) thick.  There is a DPC strip under all the blocks at floor level.

 

We have established that we need to build the floor up in order to insulate and achieve required U values.

 

We are now looking at the walls and I want to check cavity requirements.

 

I have seen conversion videos where there is no cavity and studwork is covered with a membrane and installed up against the block walls then insulated. - Not sure how to calculate the U value of this method.

 

The Kingspan U value calculator  option is 50mm cavity, studwork backed with OSB and membrane, insulation inside studs, then insulated plasterboard - to achieve required U values.  This is difficult to retrofit as I think it would need tying in?  Also would we need a cavity tray? - we could achieve this as there is enough DPC protruding from the bottom of the walls to wrap across the 100mm high sole plate, to create the slope and install weepholes.

 

Two very different methods - any advice much appreciated!

 

Thanks

[Russell griffiths]

Look up the restoration couple on you tube, your project sounds like theirs, just probably smaller. 
is this a class Q conversion or something similar. 

Edited 20 hours ago by Russell griffiths

[CharlotteJ]

43 minutes ago, Russell griffiths said:

Look up the restoration couple on you tube, your project sounds like theirs, just probably smaller. 
is this a class Q conversion or something similar. 

I dont believe it is class Q.  It was an agricultural building although a modern building rather than stone barn.  We have full PP for change of use to two dwellings - its a large C shaped building so a two bed and a 7 bed separated by an internal fire wall.

 

Thanks, I will have a search on youtube. 

[Russell griffiths]

24 minutes ago, CharlotteJ said:

I dont believe it is class Q.  It was an agricultural building although a modern building rather than stone barn.  We have full PP for change of use to two dwellings - its a large C shaped building so a two bed and a 7 bed separated by an internal fire wall.

 

Thanks, I will have a search on youtube. 

If it’s a large build then definitely look at those vids on YouTube, he’s doing an excellent job on a massive farm barn. 

[Iceverge]

Kingspan will direct you towards their own products and have a habit of playing fast and loose with some of the specs. Tragically this has included some of the fire tests too. 

 

Ubakus is free when you make an account and you can choose genetic materials. 

 

https://www.ubakus.de/en/r-value-calculator//?

 

What are your aims for the wall. What kind of U value do you need? Are you stuck for internal space. 

 

Pics/sketches would help.