U value

[Dodgy-diver]

can anyone please confirm the minimum U value for a timber framed external wall and where the info came from . I keep finding different answers 

 

im trying to find out what thickness of Celotex or similar I need 

 

thanks so much for any help 

 

[Temp]

Is it a new building or an extension? There are two versions of Part L one for each.

 

https://www.gov.uk/government/publications/conservation-of-fuel-and-power-approved-document-l

Edited November 10, 2020 by Temp

[A_L]

32 minutes ago, Dodgy-diver said:

im trying to find out what thickness of Celotex or similar I need 

 

If a new build in England allowing for a 15% timber fraction you need 120mm of PIR (U=0.295), ignoring any other fabric layers. There are variations in Scotland and I think in Wales.

[ADLIan]

For a new extension wall you need 0.28 W/m2K. For new build house it depends upon the numbers that come out of the SAP assessment, looking at better than 0.25, ideally better than 0.20.

 

After the revelations at the Grenfell Inquiry this week not sure why anyone would consider Celotex or Kingspan.

[Thorfun]

22 minutes ago, ADLIan said:

After the revelations at the Grenfell Inquiry this week not sure why anyone would consider Celotex or Kingspan.

 

just briefly read up on this and it doesn't seem that PIR was at fault and I presume your statement comes from the fact that Celotex and Kingspan knew about the issues with the PE and so should be avoided as they obviously have no morales at all.? in that case, other PIR manufacturers are available, right? 

[Dodgy-diver]

1 hour ago, Temp said:

Is it a new building or an extension? There are two versions of Part L one for each.

 

https://www.gov.uk/government/publications/conservation-of-fuel-and-power-approved-document-l

just a rear extension . many thanks 

34 minutes ago, ADLIan said:

For a new extension wall you need 0.28 W/m2K. For new build house it depends upon the numbers that come out of the SAP assessment, looking at better than 0.25, ideally better than 0.20.

 

After the revelations at the Grenfell Inquiry this week not sure why anyone would consider Celotex or Kingspan.

what would you suggest instead please

[ADLIan]

We may drift off topic here. But basically both lied about fire performance, used outdated test data, changed the chemistry of products, openly confused the market.....Does not make for good reading. Celotex also admitted overstating thermal performance just after the Grenfell fire.

Yes, other manufacturers are available.

[Thorfun]

5 minutes ago, ADLIan said:

Yes, other manufacturers are available.

but that doesn't mean the other manufacturers are any better of course!

 

it's definitely food for thought as I was planning to use some PIR in our wall make up.

[ADLIan]

Could try Recticel or Extratherm, they don’t appear to be caught up in this mess. 

[SteamyTea]

47 minutes ago, Thorfun said:

it's definitely food for thought as I was planning to use some PIR in our wall make up.

You are not building a block of flats, the fire issue was caused by a number of failings, not just one.

[A_L]

@Dodgy-diver, here is a solution using Frametherm32, U=0.26

 

https://www.buildingmaterials.co.uk/knauf-earthwool-frametherm-roll-32?ps=MjA5PTgxMDgmMzY2PTEwMzYyJjM3MT0xMDU1NCY0MzE9MTU3NTI=&gclid=EAIaIQobChMIg4z05df47AIVDO7tCh35nwObEAQYASABEgIOGfD_BwE&gclsrc=aw.ds#209=8108&366=10362&371=10554&431=15752infinity=ict2~net~gaw~ar~441793144077~kw~~mt~~cmp~Shopping_Smart+Shopping_Insulation_All~ag~Insulation+Only

[scottishjohn]

surely latest regs  for smoke detectors and linked alarms will take care of any possible problem there --

law in scotland from 2022

[Thorfun]

18 hours ago, A_L said:

@Dodgy-diver, here is a solution using Frametherm32, U=0.26

 

https://www.buildingmaterials.co.uk/knauf-earthwool-frametherm-roll-32?ps=MjA5PTgxMDgmMzY2PTEwMzYyJjM3MT0xMDU1NCY0MzE9MTU3NTI=&gclid=EAIaIQobChMIg4z05df47AIVDO7tCh35nwObEAQYASABEgIOGfD_BwE&gclsrc=aw.ds#209=8108&366=10362&371=10554&431=15752infinity=ict2~net~gaw~ar~441793144077~kw~~mt~~cmp~Shopping_Smart+Shopping_Insulation_All~ag~Insulation+Only

 

@A_L what software is that? I've been using https://www.changeplan.co.uk/u_value_calculator.php which seems to work but the software you're using looks very interesting

[A_L]

2 hours ago, Thorfun said:

what software is that?

 

It is part of a package (NHER Evaluator) which was  state of the art 2000-2010 but is no longer publically available.

[Gone West]

I used BuildDeskU which I managed to download on two occasions each for 30 days free. It had a similar looking output but I used it in 2009.

 

http://www.builddesk.co.uk/software/builddesk-u/download-builddesk-u/