Wall insulation for wood clad building

[pooksahib]

Hi. I'm being told that the proposed construction of my extension will have better insulation qualities than the existing house (which is standard brick/concrete). I find it hard to believe that two layers of what looks like fancy polystyrene will be enough to insulate a building which has an exterior wall made of wooden planks. Can anyone reassure me on this I wonder?

Thanks in advance. Here's an extract from the plans:
View media item 16750

 

[freddiemercurystwin]

A typical cavity wall construction has say 50mm insulation in the cavity, the drawing is specifying 125mm of insulation so its fairly obvious its going to better, concrete blocks and bricks offer little in the way of insulation. BTW Kooltherm K3 is about the highest spec rigid foam insulation that you can buy.

 

[pooksahib]

That's good to know, thanks for posting. I forgot to mention, however - the Kooltherm is actually going to be QuinnTherm. I'm told it's 'equal and equivalent' - would you agree?

Thanks again.

 

[freddiemercurystwin]

I believe Kingspan is slightly better (ie would need slightly less thickness), truthfully the only way to ensure a Quinn-therm solution achieves the same U Value as a Kingspan solution is to contact each manufacturer and get them to do U value calc, both manufacturers will be happy to provide such a service with a 5 minute conversation with their technical department. One assumes as this is for a domestic extension you need to achieve a U Value of less than 0.30 although your designer may intend that this construction surpasses that figure. As your construction is slightly out of the ordinary it is not very easy for us to check online hence you will need to contact the manufacturers or get your designer to do so.

 

[pooksahib]

Thank you once again. Very helpful.