Insulation questions

[richo106]

Hi All

 

I am now in the process of deciding on what insulation to go with etc

 

I was planning to have 200mm PIR under my screed but the general feeling is EPS is more cost effective so could be going for 300mm EPS. My question is jabfloor EPS70 suitable or does it need to be EPS100?

 

my next query is cavity wall insulation, the cavity on the new extension/floor can only be 100mm wide. At the minute I am looking to use Celotex Thermaclass 21 90mm cavity wall insulation but is there any other options to consider? EPS platinum beads?

 

many thanks 

[Ferdinand]

Morning, @richo106.

 

Floor

 

AIUI there are two things here.

 

1 - Insulation value, where the differences between Jabfloor EPS70 and EPS100 are marginal - 0.038 vs 0.036 u-values respectively.

 

On the U-value, you will need something like 350mm of EPS to give you the same insulation value as your 200mm of PIR.

 

EPS100 would save you ~25mm on the thickness required afaics. Significant?

 

2 - Compression strength, where it needs to take whatever weight you are putting on it without collapse.

 

According to the datasheet either seems applicable under a domestic floor.

https://www.jablite.co.uk/wp-content/uploads/2016/12/Jabfloor-70-100-150-200-250-below-slab-Technical-Data-Sheet.pdf

 

Wall

 

I think you may be constrained by building regs here depending on what type of blocks you are using for teh inner leaf and what extra you have inside the inner leaf. EPS may only barely meet the required standard depending on

 

That may force you down the PIR route. 

 

TBH I would plump for the one that insulates better, given what has happened to heating costs. Then worry about any of the house which is less insulated.

 

Ferdinand